| Message ID | 20230109205456.30618-1-andriy.shevchenko@linux.intel.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v1,1/1] pinctrl: Proofreading and updating the documentation accordingly | expand |
Hi Andy,
I love your patch! Perhaps something to improve:
[auto build test WARNING on linusw-pinctrl/devel]
[also build test WARNING on linusw-pinctrl/for-next linus/master v6.2-rc3 next-20230110]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Andy-Shevchenko/pinctrl-Proofreading-and-updating-the-documentation-accordingly/20230110-045804
base: https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl.git devel
patch link: https://lore.kernel.org/r/20230109205456.30618-1-andriy.shevchenko%40linux.intel.com
patch subject: [PATCH v1 1/1] pinctrl: Proofreading and updating the documentation accordingly
reproduce:
# https://github.com/intel-lab-lkp/linux/commit/b40cdd58f705c2e00a310f6f3fc828beaae6841f
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Andy-Shevchenko/pinctrl-Proofreading-and-updating-the-documentation-accordingly/20230110-045804
git checkout b40cdd58f705c2e00a310f6f3fc828beaae6841f
make menuconfig
# enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
make htmldocs
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
All warnings (new ones prefixed by >>):
>> Documentation/driver-api/pin-control.rst:210: WARNING: Could not lex literal_block as "c". Highlighting skipped.
vim +/c +210 Documentation/driver-api/pin-control.rst
209
> 210 .. code-block:: c
211
212 #include <linux/pinctrl/pinconf.h>
213 #include <linux/pinctrl/pinctrl.h>
214
215 #include "platform_x_pindefs.h"
216
217 static int foo_pin_config_get(struct pinctrl_dev *pctldev,
218 unsigned int offset,
219 unsigned long *config)
220 {
221 struct my_conftype conf;
222
223 ... Find setting for pin @ offset ...
224
225 *config = (unsigned long) conf;
226 }
227
228 static int foo_pin_config_set(struct pinctrl_dev *pctldev,
229 unsigned int offset,
230 unsigned long config)
231 {
232 struct my_conftype *conf = (struct my_conftype *) config;
233
234 switch (conf) {
235 case PLATFORM_X_PULL_UP:
236 ...
237 break;
238 }
239 }
240
241 static int foo_pin_config_group_get(struct pinctrl_dev *pctldev,
242 unsigned selector,
243 unsigned long *config)
244 {
245 ...
246 }
247
248 static int foo_pin_config_group_set(struct pinctrl_dev *pctldev,
249 unsigned selector,
250 unsigned long config)
251 {
252 ...
253 }
254
255 static struct pinconf_ops foo_pconf_ops = {
256 .pin_config_get = foo_pin_config_get,
257 .pin_config_set = foo_pin_config_set,
258 .pin_config_group_get = foo_pin_config_group_get,
259 .pin_config_group_set = foo_pin_config_group_set,
260 };
261
262 /* Pin config operations are handled by some pin controller */
263 static struct pinctrl_desc foo_desc = {
264 ...
265 .confops = &foo_pconf_ops,
266 };
267
On Mon, Jan 09, 2023 at 10:54:56PM +0200, Andy Shevchenko wrote: > diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst > index 0022e930e93e..0274313e9997 100644 > --- a/Documentation/driver-api/pin-control.rst > +++ b/Documentation/driver-api/pin-control.rst > @@ -11,7 +11,7 @@ This subsystem deals with: > - Multiplexing of pins, pads, fingers (etc) see below for details > > - Configuration of pins, pads, fingers (etc), such as software-controlled > - biasing and driving mode specific pins, such as pull-up/down, open drain, > + biasing and driving mode specific pins, such as pull-up, pull-down, open drain, > load capacitance etc. > > Top-level interface Immediately there is two "Define foo"s, which should have been like: ---- >8 ---- diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst index 22a82ee23a4156..57dd75fa091661 100644 --- a/Documentation/driver-api/pin-control.rst +++ b/Documentation/driver-api/pin-control.rst @@ -17,14 +17,12 @@ This subsystem deals with: Top-level interface =================== -Definition of PIN CONTROLLER: +Definitions: -- A pin controller is a piece of hardware, usually a set of registers, that +- A PIN CONTROLLER is a piece of hardware, usually a set of registers, that can control PINs. It may be able to multiplex, bias, set load capacitance, set drive strength, etc. for individual pins or groups of pins. -Definition of PIN: - - PINS are equal to pads, fingers, balls or whatever packaging input or output line you want to control and these are denoted by unsigned integers in the range 0..maxpin. This numberspace is local to each PIN CONTROLLER, so > @@ -95,7 +96,7 @@ this in our driver:: > To enable the pinctrl subsystem and the subgroups for PINMUX and PINCONF and > selected drivers, you need to select them from your machine's Kconfig entry, > since these are so tightly integrated with the machines they are used on. > -See for example arch/arm/mach-ux500/Kconfig for an example. > +See arch/arm/mach-ux500/Kconfig for an example. > > Pins usually have fancier names than this. You can find these in the datasheet > for your chip. Notice that the core pinctrl.h file provides a fancy macro Don't use "I" for technical documentation like this: ---- >8 ---- diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst index 57dd75fa091661..214a84e5a723c0 100644 --- a/Documentation/driver-api/pin-control.rst +++ b/Documentation/driver-api/pin-control.rst @@ -98,16 +98,16 @@ See arch/arm/mach-ux500/Kconfig for an example. Pins usually have fancier names than this. You can find these in the datasheet for your chip. Notice that the core pinctrl.h file provides a fancy macro -called PINCTRL_PIN() to create the struct entries. As you can see I enumerated -the pins from 0 in the upper left corner to 63 in the lower right corner. +called PINCTRL_PIN() to create the struct entries. As you can see the pins are +enumerated from 0 in the upper left corner to 63 in the lower right corner. This enumeration was arbitrarily chosen, in practice you need to think through your numbering system so that it matches the layout of registers and such things in your driver, or the code may become complicated. You must also consider matching of offsets to the GPIO ranges that may be handled by the pin controller. -For a padring with 467 pads, as opposed to actual pins, I used an enumeration -like this, walking around the edge of the chip, which seems to be industry +For a padding with 467 pads, as opposed to actual pins, the enumeration will +be like this, walking around the edge of the chip, which seems to be industry standard too (all these pads had names, too):: Also, I need to align numbers and change vertices to lines (dashes and pipes) in the enumeration loop diagram: ---- >8 ---- diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst index 214a84e5a723c0..e4938c28af14fb 100644 --- a/Documentation/driver-api/pin-control.rst +++ b/Documentation/driver-api/pin-control.rst @@ -106,17 +106,17 @@ and such things in your driver, or the code may become complicated. You must also consider matching of offsets to the GPIO ranges that may be handled by the pin controller. -For a padding with 467 pads, as opposed to actual pins, the enumeration will -be like this, walking around the edge of the chip, which seems to be industry -standard too (all these pads had names, too):: +For a padding with 467 pads, as opposed to actual pins, the enumeration will be +like a closed loop: walking around the edge of the chip, which seems to be +industry standard too (all these pads also had names):: - 0 ..... 104 - 466 105 - . . - . . - 358 224 - 357 .... 225 + 0 ----- 104 + 466 105 + | | + | | + 358 224 + 357 ----- 225 Pin groups > The pin configuration driver implements callbacks for changing pin > -configuration in the pin controller ops like this:: > +configuration in the pin controller ops like this: > + > +.. code-block:: c > > - #include <linux/pinctrl/pinctrl.h> > #include <linux/pinctrl/pinconf.h> > + #include <linux/pinctrl/pinctrl.h> > + > #include "platform_x_pindefs.h" > > static int foo_pin_config_get(struct pinctrl_dev *pctldev, > - unsigned offset, > - unsigned long *config) > + unsigned int offset, > + unsigned long *config) > { > struct my_conftype conf; > > @@ -235,28 +226,28 @@ configuration in the pin controller ops like this:: > } > > static int foo_pin_config_set(struct pinctrl_dev *pctldev, > - unsigned offset, > - unsigned long config) > + unsigned int offset, > + unsigned long config) > { > struct my_conftype *conf = (struct my_conftype *) config; > > switch (conf) { > case PLATFORM_X_PULL_UP: > ... > - } > + break; > } > } > > - static int foo_pin_config_group_get (struct pinctrl_dev *pctldev, > - unsigned selector, > - unsigned long *config) > + static int foo_pin_config_group_get(struct pinctrl_dev *pctldev, > + unsigned selector, > + unsigned long *config) > { > ... > } > > - static int foo_pin_config_group_set (struct pinctrl_dev *pctldev, > - unsigned selector, > - unsigned long config) > + static int foo_pin_config_group_set(struct pinctrl_dev *pctldev, > + unsigned selector, > + unsigned long config) > { > ... > } Sphinx reports: Documentation/driver-api/pin-control.rst:210: WARNING: Could not lex literal_block as "c". Highlighting skipped. I have to comment out "Find setting" comment: ---- >8 ---- diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst index 0274313e999722..22a82ee23a4156 100644 --- a/Documentation/driver-api/pin-control.rst +++ b/Documentation/driver-api/pin-control.rst @@ -220,7 +220,7 @@ configuration in the pin controller ops like this: { struct my_conftype conf; - ... Find setting for pin @ offset ... + /* ... Find setting for pin @ offset ... */ *config = (unsigned long) conf; } > @@ -378,7 +380,7 @@ will get a pin number into its handled number range. Further it is also passed > the range ID value, so that the pin controller knows which range it should > deal with. > > -Calling pinctrl_add_gpio_range from pinctrl driver is DEPRECATED. Please see > +Calling pinctrl_add_gpio_range() from pinctrl driver is DEPRECATED. Please see > section 2.1 of Documentation/devicetree/bindings/gpio/gpio.txt on how to bind > pinctrl and gpio drivers. > On "Pinmux conventions" subsection, the term "Definitions" is a misnomer for convention lists, so I have to correct that: ---- >8 ---- diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst index e4938c28af14fb..95333dadcbdd08 100644 --- a/Documentation/driver-api/pin-control.rst +++ b/Documentation/driver-api/pin-control.rst @@ -466,7 +466,7 @@ in your machine configuration. It is inspired by the clk, GPIO and regulator subsystems, so devices will request their mux setting, but it's also possible to request a single pin for e.g. GPIO. -Definitions: +The conventions are: - FUNCTIONS can be switched in and out by a driver residing with the pin control subsystem in the drivers/pinctrl/* directory of the kernel. The > Debugfs files > ============= > + > These files are created in ``/sys/kernel/debug/pinctrl``: > > - ``pinctrl-devices``: prints each pin controller device along with columns to > @@ -1440,7 +1428,7 @@ These files are created in ``/sys/kernel/debug/pinctrl``: > - ``pinctrl-handles``: prints each configured pin controller handle and the > corresponding pinmux maps > > -- ``pinctrl-maps``: print all pinctrl maps > +- ``pinctrl-maps``: prints all pinctrl maps > > A sub-directory is created inside of ``/sys/kernel/debug/pinctrl`` for each pin > controller device containing these files: > @@ -1448,20 +1436,22 @@ controller device containing these files: > - ``pins``: prints a line for each pin registered on the pin controller. The > pinctrl driver may add additional information such as register contents. > > -- ``gpio-ranges``: print ranges that map gpio lines to pins on the controller > +- ``gpio-ranges``: prints ranges that map gpio lines to pins on the controller > > -- ``pingroups``: print all pin groups registered on the pin controller > +- ``pingroups``: prints all pin groups registered on the pin controller > > -- ``pinconf-pins``: print pin config settings for each pin > +- ``pinconf-pins``: prints pin config settings for each pin > > -- ``pinconf-groups``: print pin config settings per pin group > +- ``pinconf-groups``: prints pin config settings per pin group > > -- ``pinmux-functions``: print each pin function along with the pin groups that > +- ``pinmux-functions``: prints each pin function along with the pin groups that > map to the pin function > > -- ``pinmux-pins``: iterate through all pins and print mux owner, gpio owner > +- ``pinmux-pins``: iterates through all pins and prints mux owner, gpio owner > and if the pin is a hog > > -- ``pinmux-select``: write to this file to activate a pin function for a group:: > +- ``pinmux-select``: write to this file to activate a pin function for a group: > + > + .. code-block:: sh > > echo "<group-name function-name>" > pinmux-select Code keywords (variables, function names, file paths) are inlined here but not on elsewhere in this doc, so I have to inline the remaining keywords: ---- >8 ---- diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst index 95333dadcbdd08..7ef6da61ea8da2 100644 --- a/Documentation/driver-api/pin-control.rst +++ b/Documentation/driver-api/pin-control.rst @@ -94,17 +94,17 @@ this in our driver: To enable the pinctrl subsystem and the subgroups for PINMUX and PINCONF and selected drivers, you need to select them from your machine's Kconfig entry, since these are so tightly integrated with the machines they are used on. -See arch/arm/mach-ux500/Kconfig for an example. +See ``arch/arm/mach-ux500/Kconfig`` for an example. Pins usually have fancier names than this. You can find these in the datasheet for your chip. Notice that the core pinctrl.h file provides a fancy macro -called PINCTRL_PIN() to create the struct entries. As you can see the pins are -enumerated from 0 in the upper left corner to 63 in the lower right corner. -This enumeration was arbitrarily chosen, in practice you need to think -through your numbering system so that it matches the layout of registers -and such things in your driver, or the code may become complicated. You must -also consider matching of offsets to the GPIO ranges that may be handled by -the pin controller. +called ``PINCTRL_PIN()`` to create the struct entries. As you can see the pins +are enumerated from 0 in the upper left corner to 63 in the lower right corner. +This enumeration was arbitrarily chosen, in practice you need to think through +your numbering system so that it matches the layout of registers and such +things in your driver, or the code may become complicated. You must also +consider matching of offsets to the GPIO ranges that may be handled by the pin +controller. For a padding with 467 pads, as opposed to actual pins, the enumeration will be like a closed loop: walking around the edge of the chip, which seems to be @@ -131,7 +131,7 @@ on { 0, 8, 16, 24 }, and a group of pins dealing with an I2C interface on pins on { 24, 25 }. These two groups are presented to the pin control subsystem by implementing -some generic pinctrl_ops like this: +some generic ``pinctrl_ops`` like this: .. code-block:: c @@ -177,7 +177,7 @@ some generic pinctrl_ops like this: .pctlops = &foo_pctrl_ops, }; -The pin control subsystem will call the .get_groups_count() function to +The pin control subsystem will call the ``.get_groups_count()`` function to determine the total number of legal selectors, then it will call the other functions to retrieve the name and pins of the group. Maintaining the data structure of the groups is up to the driver, this is just a simple example - in practice you @@ -199,7 +199,7 @@ unconnected. Pin configuration can be programmed by adding configuration entries into the mapping table; see section `Board/machine configuration`_ below. -The format and meaning of the configuration parameter, PLATFORM_X_PULL_UP +The format and meaning of the configuration parameter, ``PLATFORM_X_PULL_UP`` above, is entirely defined by the pin controller driver. The pin configuration driver implements callbacks for changing pin @@ -318,23 +318,23 @@ like this: ... } -So this complex system has one pin controller handling two different -GPIO chips. "chip a" has 16 pins and "chip b" has 8 pins. The "chip a" and -"chip b" have different .pin_base, which means a start pin number of the +So this complex system has one pin controller handling two different GPIO +chips. ``chip_a`` has 16 pins and ``chip_b`` has 8 pins. The ``chip a`` and +``chip_b`` have different ``.pin_base``, which means a start pin number of the GPIO range. -The GPIO range of "chip a" starts from the GPIO base of 32 and actual -pin range also starts from 32. However "chip b" has different starting -offset for the GPIO range and pin range. The GPIO range of "chip b" starts -from GPIO number 48, while the pin range of "chip b" starts from 64. +The GPIO range of ``chip_a`` starts from the GPIO base of 32 and actual +pin range also starts from 32. However ``chip_b`` has different starting +offset for the GPIO range and pin range. The GPIO range of ``chip_b`` starts +from GPIO number 48, while the pin range of ``chip b`` starts from 64. -We can convert a gpio number to actual pin number using this "pin_base". +We can convert a gpio number to actual pin number using this ``pin_base``. They are mapped in the global GPIO pin space at: -chip a: +``chip_a``: - GPIO range : [32 .. 47] - pin range : [32 .. 47] -chip b: +``chip_b``: - GPIO range : [48 .. 55] - pin range : [64 .. 71] @@ -355,9 +355,9 @@ numbers can be encoded in the range like this: .gc = &chip, }; -In this case the pin_base property will be ignored. If the name of a pin +In this case the ``pin_base property`` will be ignored. If the name of a pin group is known, the pins and npins elements of the above structure can be -initialised using the function pinctrl_get_group_pins(), e.g. for pin +initialised using the function ``pinctrl_get_group_pins()``, e.g. for pin group "foo": .. code-block:: c @@ -378,15 +378,15 @@ will get a pin number into its handled number range. Further it is also passed the range ID value, so that the pin controller knows which range it should deal with. -Calling pinctrl_add_gpio_range() from pinctrl driver is DEPRECATED. Please see -section 2.1 of Documentation/devicetree/bindings/gpio/gpio.txt on how to bind -pinctrl and gpio drivers. +Calling ``pinctrl_add_gpio_range()`` from pinctrl driver is DEPRECATED. Please +see section 2.1 of ``Documentation/devicetree/bindings/gpio/gpio.txt`` on how +to bind pinctrl and gpio drivers. PINMUX interfaces ================= -These calls use the pinmux_* naming prefix. No other calls should use that +These calls use the ``pinmux_*`` naming prefix. No other calls should use that prefix. @@ -469,7 +469,7 @@ to request a single pin for e.g. GPIO. The conventions are: - FUNCTIONS can be switched in and out by a driver residing with the pin - control subsystem in the drivers/pinctrl/* directory of the kernel. The + control subsystem in the ``drivers/pinctrl/*`` directory of the kernel. The pin control driver knows the possible functions. In the example above you can identify three pinmux functions, one for spi, one for i2c and one for mmc. @@ -513,9 +513,9 @@ The conventions are: the core will simply select the first and only group available.) In the example case we can define that this particular machine shall - use device spi0 with pinmux function fspi0 group gspi0 and i2c0 on function - fi2c0 group gi2c0, on the primary pin controller, we get mappings - like these: + use device ``spi0`` with pinmux function ``fspi0`` group ``gspi0`` and + ``i2c0`` on function ``fi2c0`` group ``gi2c0``, on the primary pin + controller, we get mappings like these: .. code-block:: c @@ -571,8 +571,9 @@ is possible to perform the requested mux setting, poke the hardware so that this happens. Pinmux drivers are required to supply a few callback functions, some are -optional. Usually the .set_mux() function is implemented, writing values into -some certain registers to activate a certain mux setting for a certain pin. +optional. Usually the ``.set_mux()`` function is implemented, writing values +into some certain registers to activate a certain mux setting for a certain +pin. A simple driver for the above example will work by setting bits 0, 1, 2, 3, 4, or 5 into some register named MUX to select a certain function with a certain @@ -696,19 +697,20 @@ All the above functions are mandatory to implement for a pinmux driver. Pin control interaction with the GPIO subsystem =============================================== -Note that the following implies that the use case is to use a certain pin -from the Linux kernel using the API in <linux/gpio/consumer.h> with gpiod_get() -and similar functions. There are cases where you may be using something -that your datasheet calls "GPIO mode", but actually is just an electrical -configuration for a certain device. See the section below named +Note that the following implies that the use case is to use a certain pin from +the Linux kernel using the API in ``<linux/gpio/consumer.h>`` with +gpiod_get() and similar functions. There are cases where you may be using +something that your datasheet calls "GPIO mode", but actually is just an +electrical configuration for a certain device. See the section below named `GPIO mode pitfalls`_ for more details on this scenario. -The public pinmux API contains two functions named pinctrl_gpio_request() -and pinctrl_gpio_free(). These two functions shall *ONLY* be called from -gpiolib-based drivers as part of their .request() and .free() semantics. -Likewise the pinctrl_gpio_direction_input()/pinctrl_gpio_direction_output() -shall only be called from within respective .direction_input() / -.direction_output() gpiolib implementation. +The public pinmux API contains two functions named ``pinctrl_gpio_request()`` +and ``pinctrl_gpio_free()``. These two functions shall *ONLY* be called from +gpiolib-based drivers as part of their ``.request()`` and ``.free()`` +semantics. Likewise the +``pinctrl_gpio_direction_input()``/``pinctrl_gpio_direction_output()`` shall +only be called from within respective ``.direction_input()`` / +``.direction_output()`` gpiolib implementation. NOTE that platforms and individual drivers shall *NOT* request GPIO pins to be controlled e.g. muxed in. Instead, implement a proper gpiolib driver and have @@ -722,8 +724,8 @@ In this case, the function array would become 64 entries for each GPIO setting and then the device functions. For this reason there are two functions a pin control driver can implement -to enable only GPIO on an individual pin: .gpio_request_enable() and -.gpio_disable_free(). +to enable only GPIO on an individual pin: ``.gpio_request_enable()`` and +``.gpio_disable_free()``. This function will pass in the affected GPIO range identified by the pin controller core, so you know which GPIO pins are being affected by the request @@ -731,27 +733,27 @@ operation. If your driver needs to have an indication from the framework of whether the GPIO pin shall be used for input or output you can implement the -.gpio_set_direction() function. As described this shall be called from the +``.gpio_set_direction()`` function. As described this shall be called from the gpiolib driver and the affected GPIO range, pin offset and desired direction will be passed along to this function. Alternatively to using these special functions, it is fully allowed to use -named functions for each GPIO pin, the pinctrl_gpio_request() will attempt to -obtain the function "gpioN" where "N" is the global GPIO pin number if no -special GPIO-handler is registered. +named functions for each GPIO pin, the ``pinctrl_gpio_request()`` will attempt +to obtain the function ``gpioN`` where ``N`` is the global GPIO pin number if +no special GPIO-handler is registered. GPIO mode pitfalls ================== -Due to the naming conventions used by hardware engineers, where "GPIO" -is taken to mean different things than what the kernel does, the developer -may be confused by a datasheet talking about a pin being possible to set -into "GPIO mode". It appears that what hardware engineers mean with -"GPIO mode" is not necessarily the use case that is implied in the kernel -interface <linux/gpio/consumer.h>: a pin that you grab from kernel code and then -either listen for input or drive high/low to assert/deassert some -external line. +Due to the naming conventions used by hardware engineers, where "GPIO" is taken +to mean different things than what the kernel does, the developer may be +confused by a datasheet talking about a pin being possible to set into "GPIO +mode". It appears that what hardware engineers mean with "GPIO mode" is not +necessarily the use case that is implied in the kernel interface +``<linux/gpio/consumer.h>``: a pin that you grab from kernel code and then +either listen for input or drive high/low to assert/deassert some external +line. Rather hardware engineers think that "GPIO mode" means that you can software-control a few electrical properties of the pin that you would @@ -859,8 +861,8 @@ wake up and maybe even gpiod_get()/gpiod_put() as part of this cycle. This all gets very complicated. The solution is to not think that what the datasheet calls "GPIO mode" -has to be handled by the <linux/gpio/consumer.h> interface. Instead view this as -a certain pin config setting. Look in e.g. <linux/pinctrl/pinconf-generic.h> +has to be handled by the ``<linux/gpio/consumer.h>`` interface. Instead view this as +a certain pin config setting. Look in e.g. ``<linux/pinctrl/pinconf-generic.h>`` and you find this in the documentation: PIN_CONFIG_OUTPUT: @@ -1038,7 +1040,7 @@ Finally, some devices expect the mapping table to contain certain specific named states. When running on hardware that doesn't need any pin controller configuration, the mapping table must still contain those named states, in order to explicitly indicate that the states were provided and intended to -be empty. Table entry macro PIN_MAP_DUMMY_STATE serves the purpose of defining +be empty. Table entry macro ``PIN_MAP_DUMMY_STATE`` serves the purpose of defining a named state without causing any pin controller to be programmed: .. code-block:: c @@ -1163,7 +1165,7 @@ Pin control requests from drivers ================================= When a device driver is about to probe the device core will automatically -attempt to issue pinctrl_get_select_default() on these devices. +attempt to issue ``pinctrl_get_select_default()`` on these devices. This way driver writers do not need to add any of the boilerplate code of the type found below. However when doing fine-grained state selection and not using the "default" state, you may have to do some device driver @@ -1181,8 +1183,8 @@ some cases where a driver needs to e.g. switch between different mux mappings at runtime this is not possible. A typical case is if a driver needs to switch bias of pins from normal -operation and going to sleep, moving from the PINCTRL_STATE_DEFAULT to -PINCTRL_STATE_SLEEP at runtime, re-biasing or even re-muxing pins to save +operation and going to sleep, moving from the ``PINCTRL_STATE_DEFAULT`` to +``PINCTRL_STATE_SLEEP`` at runtime, re-biasing or even re-muxing pins to save current in sleep mode. A driver may request a certain control state to be activated, usually just the @@ -1228,49 +1230,49 @@ arrangement on your bus. The semantics of the pinctrl APIs are: -- pinctrl_get() is called in process context to obtain a handle to all pinctrl - information for a given client device. It will allocate a struct from the - kernel memory to hold the pinmux state. All mapping table parsing or similar - slow operations take place within this API. +- ``pinctrl_get()`` is called in process context to obtain a handle to all + pinctrl information for a given client device. It will allocate a struct from + the kernel memory to hold the pinmux state. All mapping table parsing or + similar slow operations take place within this API. -- devm_pinctrl_get() is a variant of pinctrl_get() that causes pinctrl_put() - to be called automatically on the retrieved pointer when the associated - device is removed. It is recommended to use this function over plain - pinctrl_get(). +- ``devm_pinctrl_get()`` is a variant of ``pinctrl_get()`` that causes + ``pinctrl_put()`` to be called automatically on the retrieved pointer when + the associated device is removed. It is recommended to use this function over + plain ``pinctrl_get()``. -- pinctrl_lookup_state() is called in process context to obtain a handle to a - specific state for a client device. This operation may be slow, too. +- ``pinctrl_lookup_state()`` is called in process context to obtain a handle to + a specific state for a client device. This operation may be slow, too. -- pinctrl_select_state() programs pin controller hardware according to the +- ``pinctrl_select_state()`` programs pin controller hardware according to the definition of the state as given by the mapping table. In theory, this is a fast-path operation, since it only involved blasting some register settings into hardware. However, note that some pin controllers may have their registers on a slow/IRQ-based bus, so client devices should not assume they - can call pinctrl_select_state() from non-blocking contexts. + can call ``pinctrl_select_state()`` from non-blocking contexts. -- pinctrl_put() frees all information associated with a pinctrl handle. +- ``pinctrl_put()`` frees all information associated with a pinctrl handle. -- devm_pinctrl_put() is a variant of pinctrl_put() that may be used to - explicitly destroy a pinctrl object returned by devm_pinctrl_get(). - However, use of this function will be rare, due to the automatic cleanup - that will occur even without calling it. +- ``devm_pinctrl_put()`` is a variant of ``pinctrl_put()`` that may be used to + explicitly destroy a pinctrl object returned by ``devm_pinctrl_get()``. + However, use of this function will be rare, due to the automatic cleanup that + will occur even without calling it. - pinctrl_get() must be paired with a plain pinctrl_put(). - pinctrl_get() may not be paired with devm_pinctrl_put(). - devm_pinctrl_get() can optionally be paired with devm_pinctrl_put(). - devm_pinctrl_get() may not be paired with plain pinctrl_put(). + ``pinctrl_get()`` must be paired with a ``plain pinctrl_put()``. + ``pinctrl_get()`` may not be paired with ``devm_pinctrl_put()``. + ``devm_pinctrl_get()`` can optionally be paired with ``devm_pinctrl_put()``. + ``devm_pinctrl_get()`` may not be paired with plain ``pinctrl_put()``. Usually the pin control core handled the get/put pair and call out to the device drivers bookkeeping operations, like checking available functions and -the associated pins, whereas pinctrl_select_state() pass on to the pin controller -driver which takes care of activating and/or deactivating the mux setting by -quickly poking some registers. +the associated pins, whereas ``pinctrl_select_state()`` pass on to the pin +controller driver which takes care of activating and/or deactivating the mux +setting by quickly poking some registers. -The pins are allocated for your device when you issue the devm_pinctrl_get() -call, after this you should be able to see this in the debugfs listing of all -pins. +The pins are allocated for your device when you issue the +``devm_pinctrl_get()`` call, after this you should be able to see this in the +debugfs listing of all pins. -NOTE: the pinctrl system will return -EPROBE_DEFER if it cannot find the +NOTE: the pinctrl system will return ``-EPROBE_DEFER`` if it cannot find the requested pinctrl handles, for example if the pinctrl driver has not yet registered. Thus make sure that the error path in your driver gracefully cleans up and is ready to retry the probing later in the startup process. @@ -1295,7 +1297,7 @@ So say that your driver is fetching its resources like this: pinctrl = devm_pinctrl_get_select_default(&dev); gpio = devm_gpiod_get(&dev, "foo"); -Here we first request a certain pin state and then request GPIO "foo" to be +Here we first request a certain pin state and then request GPIO ``foo`` to be used. If you're using the subsystems orthogonally like this, you should nominally always get your pinctrl handle and select the desired pinctrl state BEFORE requesting the GPIO. This is a semantic convention to avoid @@ -1312,7 +1314,7 @@ to communicate directly with the pinctrl subsystem, using the latter as a back-end. This is when the GPIO driver may call out to the functions described in the section `Pin control interaction with the GPIO subsystem`_ above. This only involves per-pin multiplexing, and will be completely -hidden behind the gpiod_*() function namespace. In this case, the driver +hidden behind the ``gpiod_*()`` function namespace. In this case, the driver need not interact with the pin control subsystem at all. If a pin control driver and a GPIO driver is dealing with the same pins @@ -1326,13 +1328,14 @@ pin control system. System pin control hogging ========================== -Pin control map entries can be hogged by the core when the pin controller -is registered. This means that the core will attempt to call pinctrl_get(), -pinctrl_lookup_state() and pinctrl_select_state() on it immediately after -the pin control device has been registered. +Pin control map entries can be hogged by the core when the pin controller is +registered. This means that the core will attempt to call ``pinctrl_get()``, +``pinctrl_lookup_state()`` and ``pinctrl_select_state()`` on it immediately +after the pin control device has been registered. -This occurs for mapping table entries where the client device name is equal -to the pin controller device name, and the state name is PINCTRL_STATE_DEFAULT: +This occurs for mapping table entries where the client device name is equal to +the pin controller device name, and the state name is +``PINCTRL_STATE_DEFAULT``: .. code-block:: c @@ -1366,9 +1369,9 @@ function, but with different named in the mapping as described under "Advanced mapping" above. So that for an SPI device, we have two states named "pos-A" and "pos-B". -This snippet first initializes a state object for both groups (in foo_probe()), -then muxes the function in the pins defined by group A, and finally muxes it in -on the pins defined by group B: +This snippet first initializes a state object for both groups (in +``foo_probe()``), then muxes the function in the pins defined by group A, and +finally muxes it in on the pins defined by group B: .. code-block:: c Thanks.
On Tue, Jan 10, 2023 at 04:13:00PM +0700, Bagas Sanjaya wrote: > On Mon, Jan 09, 2023 at 10:54:56PM +0200, Andy Shevchenko wrote: > > diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst > > index 0022e930e93e..0274313e9997 100644 > > --- a/Documentation/driver-api/pin-control.rst > > +++ b/Documentation/driver-api/pin-control.rst > > @@ -11,7 +11,7 @@ This subsystem deals with: > > - Multiplexing of pins, pads, fingers (etc) see below for details > > > > - Configuration of pins, pads, fingers (etc), such as software-controlled > > - biasing and driving mode specific pins, such as pull-up/down, open drain, > > + biasing and driving mode specific pins, such as pull-up, pull-down, open drain, > > load capacitance etc. > > > > Top-level interface Thank you for your input, can I add it as a separate change on top of mine? I would like to keep my stuff separate from the more intrusive changes (scope is mostly on the examples and function references). If yes, can you provide your SoB tag? Btw, the pad table is not align on purpose AFAIU how BGA looks from the bottom.
On Thu, Jan 12, 2023 at 01:46:20PM +0200, Andy Shevchenko wrote: > Thank you for your input, can I add it as a separate change on top of mine? I would like to keep > my stuff separate from the more intrusive changes (scope is mostly on the examples and function > references). If yes, can you provide your SoB tag? > Yes, please do. And for the trailers: Co-developed-by: Bagas Sanjaya <bagasdotme@gmail.com> Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
diff --git a/Documentation/driver-api/pin-control.rst b/Documentation/driver-api/pin-control.rst index 0022e930e93e..0274313e9997 100644 --- a/Documentation/driver-api/pin-control.rst +++ b/Documentation/driver-api/pin-control.rst @@ -11,7 +11,7 @@ This subsystem deals with: - Multiplexing of pins, pads, fingers (etc) see below for details - Configuration of pins, pads, fingers (etc), such as software-controlled - biasing and driving mode specific pins, such as pull-up/down, open drain, + biasing and driving mode specific pins, such as pull-up, pull-down, open drain, load capacitance etc. Top-level interface @@ -57,7 +57,9 @@ Here is an example of a PGA (Pin Grid Array) chip seen from underneath:: 1 o o o o o o o o To register a pin controller and name all the pins on this package we can do -this in our driver:: +this in our driver: + +.. code-block:: c #include <linux/pinctrl/pinctrl.h> @@ -78,14 +80,13 @@ this in our driver:: .owner = THIS_MODULE, }; - int __init foo_probe(void) + int __init foo_init(void) { int error; struct pinctrl_dev *pctl; - error = pinctrl_register_and_init(&foo_desc, <PARENT>, - NULL, &pctl); + error = pinctrl_register_and_init(&foo_desc, <PARENT>, NULL, &pctl); if (error) return error; @@ -95,7 +96,7 @@ this in our driver:: To enable the pinctrl subsystem and the subgroups for PINMUX and PINCONF and selected drivers, you need to select them from your machine's Kconfig entry, since these are so tightly integrated with the machines they are used on. -See for example arch/arm/mach-ux500/Kconfig for an example. +See arch/arm/mach-ux500/Kconfig for an example. Pins usually have fancier names than this. You can find these in the datasheet for your chip. Notice that the core pinctrl.h file provides a fancy macro @@ -132,50 +133,38 @@ on { 0, 8, 16, 24 }, and a group of pins dealing with an I2C interface on pins on { 24, 25 }. These two groups are presented to the pin control subsystem by implementing -some generic pinctrl_ops like this:: +some generic pinctrl_ops like this: - #include <linux/pinctrl/pinctrl.h> +.. code-block:: c - struct foo_group { - const char *name; - const unsigned int *pins; - const unsigned num_pins; - }; + #include <linux/pinctrl/pinctrl.h> static const unsigned int spi0_pins[] = { 0, 8, 16, 24 }; static const unsigned int i2c0_pins[] = { 24, 25 }; - static const struct foo_group foo_groups[] = { - { - .name = "spi0_grp", - .pins = spi0_pins, - .num_pins = ARRAY_SIZE(spi0_pins), - }, - { - .name = "i2c0_grp", - .pins = i2c0_pins, - .num_pins = ARRAY_SIZE(i2c0_pins), - }, + static const struct pingroup foo_groups[] = { + PINCTRL_PINGROUP("spi0_grp", spi0_pins, ARRAY_SIZE(spi0_pins)), + PINCTRL_PINGROUP("i2c0_grp", i2c0_pins, ARRAY_SIZE(i2c0_pins)), }; - static int foo_get_groups_count(struct pinctrl_dev *pctldev) { return ARRAY_SIZE(foo_groups); } static const char *foo_get_group_name(struct pinctrl_dev *pctldev, - unsigned selector) + unsigned int selector) { return foo_groups[selector].name; } - static int foo_get_group_pins(struct pinctrl_dev *pctldev, unsigned selector, - const unsigned **pins, - unsigned *num_pins) + static int foo_get_group_pins(struct pinctrl_dev *pctldev, + unsigned int selector, + const unsigned int **pins, + unsigned int *npins) { - *pins = (unsigned *) foo_groups[selector].pins; - *num_pins = foo_groups[selector].num_pins; + *pins = foo_groups[selector].pins; + *npins = foo_groups[selector].npins; return 0; } @@ -185,10 +174,9 @@ some generic pinctrl_ops like this:: .get_group_pins = foo_get_group_pins, }; - static struct pinctrl_desc foo_desc = { - ... - .pctlops = &foo_pctrl_ops, + ... + .pctlops = &foo_pctrl_ops, }; The pin control subsystem will call the .get_groups_count() function to @@ -204,28 +192,31 @@ Pin configuration Pins can sometimes be software-configured in various ways, mostly related to their electronic properties when used as inputs or outputs. For example you -may be able to make an output pin high impedance, or "tristate" meaning it is +may be able to make an output pin high impedance (Hi-Z), or "tristate" meaning it is effectively disconnected. You may be able to connect an input pin to VDD or GND using a certain resistor value - pull up and pull down - so that the pin has a stable value when nothing is driving the rail it is connected to, or when it's unconnected. Pin configuration can be programmed by adding configuration entries into the -mapping table; see section "Board/machine configuration" below. +mapping table; see section `Board/machine configuration`_ below. The format and meaning of the configuration parameter, PLATFORM_X_PULL_UP above, is entirely defined by the pin controller driver. The pin configuration driver implements callbacks for changing pin -configuration in the pin controller ops like this:: +configuration in the pin controller ops like this: + +.. code-block:: c - #include <linux/pinctrl/pinctrl.h> #include <linux/pinctrl/pinconf.h> + #include <linux/pinctrl/pinctrl.h> + #include "platform_x_pindefs.h" static int foo_pin_config_get(struct pinctrl_dev *pctldev, - unsigned offset, - unsigned long *config) + unsigned int offset, + unsigned long *config) { struct my_conftype conf; @@ -235,28 +226,28 @@ configuration in the pin controller ops like this:: } static int foo_pin_config_set(struct pinctrl_dev *pctldev, - unsigned offset, - unsigned long config) + unsigned int offset, + unsigned long config) { struct my_conftype *conf = (struct my_conftype *) config; switch (conf) { case PLATFORM_X_PULL_UP: ... - } + break; } } - static int foo_pin_config_group_get (struct pinctrl_dev *pctldev, - unsigned selector, - unsigned long *config) + static int foo_pin_config_group_get(struct pinctrl_dev *pctldev, + unsigned selector, + unsigned long *config) { ... } - static int foo_pin_config_group_set (struct pinctrl_dev *pctldev, - unsigned selector, - unsigned long config) + static int foo_pin_config_group_set(struct pinctrl_dev *pctldev, + unsigned selector, + unsigned long config) { ... } @@ -281,8 +272,8 @@ The GPIO drivers may want to perform operations of various types on the same physical pins that are also registered as pin controller pins. First and foremost, the two subsystems can be used as completely orthogonal, -see the section named "pin control requests from drivers" and -"drivers needing both pin control and GPIOs" below for details. But in some +see the section named `Pin control requests from drivers`_ and +`Drivers needing both pin control and GPIOs`_ below for details. But in some situations a cross-subsystem mapping between pins and GPIOs is needed. Since the pin controller subsystem has its pinspace local to the pin controller @@ -291,7 +282,13 @@ controller handles control of a certain GPIO pin. Since a single pin controller may be muxing several GPIO ranges (typically SoCs that have one set of pins, but internally several GPIO silicon blocks, each modelled as a struct gpio_chip) any number of GPIO ranges can be added to a pin controller instance -like this:: +like this: + +.. code-block:: c + + #include <linux/gpio/driver.h> + + #include <linux/pinctrl/pinctrl.h> struct gpio_chip chip_a; struct gpio_chip chip_b; @@ -302,7 +299,7 @@ like this:: .base = 32, .pin_base = 32, .npins = 16, - .gc = &chip_a; + .gc = &chip_a, }; static struct pinctrl_gpio_range gpio_range_b = { @@ -314,11 +311,13 @@ like this:: .gc = &chip_b; }; + int __init foo_init(void) { struct pinctrl_dev *pctl; ... pinctrl_add_gpio_range(pctl, &gpio_range_a); pinctrl_add_gpio_range(pctl, &gpio_range_b); + ... } So this complex system has one pin controller handling two different @@ -343,9 +342,11 @@ chip b: The above examples assume the mapping between the GPIOs and pins is linear. If the mapping is sparse or haphazard, an array of arbitrary pin -numbers can be encoded in the range like this:: +numbers can be encoded in the range like this: - static const unsigned range_pins[] = { 14, 1, 22, 17, 10, 8, 6, 2 }; +.. code-block:: c + + static const unsigned int range_pins[] = { 14, 1, 22, 17, 10, 8, 6, 2 }; static struct pinctrl_gpio_range gpio_range = { .name = "chip", @@ -353,16 +354,17 @@ numbers can be encoded in the range like this:: .base = 32, .pins = &range_pins, .npins = ARRAY_SIZE(range_pins), - .gc = &chip; + .gc = &chip, }; In this case the pin_base property will be ignored. If the name of a pin group is known, the pins and npins elements of the above structure can be initialised using the function pinctrl_get_group_pins(), e.g. for pin -group "foo":: +group "foo": + +.. code-block:: c - pinctrl_get_group_pins(pctl, "foo", &gpio_range.pins, - &gpio_range.npins); + pinctrl_get_group_pins(pctl, "foo", &gpio_range.pins, &gpio_range.npins); When GPIO-specific functions in the pin control subsystem are called, these ranges will be used to look up the appropriate pin controller by inspecting @@ -378,7 +380,7 @@ will get a pin number into its handled number range. Further it is also passed the range ID value, so that the pin controller knows which range it should deal with. -Calling pinctrl_add_gpio_range from pinctrl driver is DEPRECATED. Please see +Calling pinctrl_add_gpio_range() from pinctrl driver is DEPRECATED. Please see section 2.1 of Documentation/devicetree/bindings/gpio/gpio.txt on how to bind pinctrl and gpio drivers. @@ -515,11 +517,13 @@ Definitions: In the example case we can define that this particular machine shall use device spi0 with pinmux function fspi0 group gspi0 and i2c0 on function fi2c0 group gi2c0, on the primary pin controller, we get mappings - like these:: + like these: + + .. code-block:: c { {"map-spi0", spi0, pinctrl0, fspi0, gspi0}, - {"map-i2c0", i2c0, pinctrl0, fi2c0, gi2c0} + {"map-i2c0", i2c0, pinctrl0, fi2c0, gi2c0}, } Every map must be assigned a state name, pin controller, device and @@ -569,80 +573,51 @@ is possible to perform the requested mux setting, poke the hardware so that this happens. Pinmux drivers are required to supply a few callback functions, some are -optional. Usually the set_mux() function is implemented, writing values into +optional. Usually the .set_mux() function is implemented, writing values into some certain registers to activate a certain mux setting for a certain pin. -A simple driver for the above example will work by setting bits 0, 1, 2, 3 or 4 +A simple driver for the above example will work by setting bits 0, 1, 2, 3, 4, or 5 into some register named MUX to select a certain function with a certain -group of pins would work something like this:: +group of pins would work something like this: + +.. code-block:: c #include <linux/pinctrl/pinctrl.h> #include <linux/pinctrl/pinmux.h> - struct foo_group { - const char *name; - const unsigned int *pins; - const unsigned num_pins; - }; - - static const unsigned spi0_0_pins[] = { 0, 8, 16, 24 }; - static const unsigned spi0_1_pins[] = { 38, 46, 54, 62 }; - static const unsigned i2c0_pins[] = { 24, 25 }; - static const unsigned mmc0_1_pins[] = { 56, 57 }; - static const unsigned mmc0_2_pins[] = { 58, 59 }; - static const unsigned mmc0_3_pins[] = { 60, 61, 62, 63 }; - - static const struct foo_group foo_groups[] = { - { - .name = "spi0_0_grp", - .pins = spi0_0_pins, - .num_pins = ARRAY_SIZE(spi0_0_pins), - }, - { - .name = "spi0_1_grp", - .pins = spi0_1_pins, - .num_pins = ARRAY_SIZE(spi0_1_pins), - }, - { - .name = "i2c0_grp", - .pins = i2c0_pins, - .num_pins = ARRAY_SIZE(i2c0_pins), - }, - { - .name = "mmc0_1_grp", - .pins = mmc0_1_pins, - .num_pins = ARRAY_SIZE(mmc0_1_pins), - }, - { - .name = "mmc0_2_grp", - .pins = mmc0_2_pins, - .num_pins = ARRAY_SIZE(mmc0_2_pins), - }, - { - .name = "mmc0_3_grp", - .pins = mmc0_3_pins, - .num_pins = ARRAY_SIZE(mmc0_3_pins), - }, + static const unsigned int spi0_0_pins[] = { 0, 8, 16, 24 }; + static const unsigned int spi0_1_pins[] = { 38, 46, 54, 62 }; + static const unsigned int i2c0_pins[] = { 24, 25 }; + static const unsigned int mmc0_1_pins[] = { 56, 57 }; + static const unsigned int mmc0_2_pins[] = { 58, 59 }; + static const unsigned int mmc0_3_pins[] = { 60, 61, 62, 63 }; + + static const struct pingroup foo_groups[] = { + PINCTRL_PINGROUP("spi0_0_grp", spi0_0_pins, ARRAY_SIZE(spi0_0_pins)), + PINCTRL_PINGROUP("spi0_1_grp", spi0_1_pins, ARRAY_SIZE(spi0_1_pins)), + PINCTRL_PINGROUP("i2c0_grp", i2c0_pins, ARRAY_SIZE(i2c0_pins)), + PINCTRL_PINGROUP("mmc0_1_grp", mmc0_1_pins, ARRAY_SIZE(mmc0_1_pins)), + PINCTRL_PINGROUP("mmc0_2_grp", mmc0_2_pins, ARRAY_SIZE(mmc0_2_pins)), + PINCTRL_PINGROUP("mmc0_3_grp", mmc0_3_pins, ARRAY_SIZE(mmc0_3_pins)), }; - static int foo_get_groups_count(struct pinctrl_dev *pctldev) { return ARRAY_SIZE(foo_groups); } static const char *foo_get_group_name(struct pinctrl_dev *pctldev, - unsigned selector) + unsigned int selector) { return foo_groups[selector].name; } - static int foo_get_group_pins(struct pinctrl_dev *pctldev, unsigned selector, - const unsigned ** pins, - unsigned * num_pins) + static int foo_get_group_pins(struct pinctrl_dev *pctldev, unsigned int selector, + const unsigned int **pins, + unsigned int *npins) { - *pins = (unsigned *) foo_groups[selector].pins; - *num_pins = foo_groups[selector].num_pins; + *pins = foo_groups[selector].pins; + *npins = foo_groups[selector].npins; return 0; } @@ -652,33 +627,14 @@ group of pins would work something like this:: .get_group_pins = foo_get_group_pins, }; - struct foo_pmx_func { - const char *name; - const char * const *groups; - const unsigned num_groups; - }; - static const char * const spi0_groups[] = { "spi0_0_grp", "spi0_1_grp" }; static const char * const i2c0_groups[] = { "i2c0_grp" }; - static const char * const mmc0_groups[] = { "mmc0_1_grp", "mmc0_2_grp", - "mmc0_3_grp" }; + static const char * const mmc0_groups[] = { "mmc0_1_grp", "mmc0_2_grp", "mmc0_3_grp" }; - static const struct foo_pmx_func foo_functions[] = { - { - .name = "spi0", - .groups = spi0_groups, - .num_groups = ARRAY_SIZE(spi0_groups), - }, - { - .name = "i2c0", - .groups = i2c0_groups, - .num_groups = ARRAY_SIZE(i2c0_groups), - }, - { - .name = "mmc0", - .groups = mmc0_groups, - .num_groups = ARRAY_SIZE(mmc0_groups), - }, + static const struct pinfunction foo_functions[] = { + PINCTRL_PINFUNCTION("spi0", spi0_groups, ARRAY_SIZE(spi0_groups)), + PINCTRL_PINFUNCTION("i2c0", i2c0_groups, ARRAY_SIZE(i2c0_groups)), + PINCTRL_PINFUNCTION("mmc0", mmc0_groups, ARRAY_SIZE(mmc0_groups)), }; static int foo_get_functions_count(struct pinctrl_dev *pctldev) @@ -686,26 +642,26 @@ group of pins would work something like this:: return ARRAY_SIZE(foo_functions); } - static const char *foo_get_fname(struct pinctrl_dev *pctldev, unsigned selector) + static const char *foo_get_fname(struct pinctrl_dev *pctldev, unsigned int selector) { return foo_functions[selector].name; } - static int foo_get_groups(struct pinctrl_dev *pctldev, unsigned selector, - const char * const **groups, - unsigned * const num_groups) + static int foo_get_groups(struct pinctrl_dev *pctldev, unsigned int selector, + const char * const **groups, + unsigned int * const ngroups) { *groups = foo_functions[selector].groups; - *num_groups = foo_functions[selector].num_groups; + *ngroups = foo_functions[selector].ngroups; return 0; } - static int foo_set_mux(struct pinctrl_dev *pctldev, unsigned selector, - unsigned group) + static int foo_set_mux(struct pinctrl_dev *pctldev, unsigned int selector, + unsigned int group) { - u8 regbit = (1 << selector + group); + u8 regbit = BIT(group); - writeb((readb(MUX)|regbit), MUX); + writeb((readb(MUX) | regbit), MUX); return 0; } @@ -724,16 +680,17 @@ group of pins would work something like this:: .pmxops = &foo_pmxops, }; -In the example activating muxing 0 and 1 at the same time setting bits -0 and 1, uses one pin in common so they would collide. +In the example activating muxing 0 and 2 at the same time setting bits +0 and 2, uses pin 24 in common so they would collide. All the same for +the muxes 1 and 5, which have pin 62 in common. The beauty of the pinmux subsystem is that since it keeps track of all pins and who is using them, it will already have denied an impossible request like that, so the driver does not need to worry about such things - when it gets a selector passed in, the pinmux subsystem makes sure no other device or GPIO assignment is already using the selected -pins. Thus bits 0 and 1 in the control register will never be set at the -same time. +pins. Thus bits 0 and 2, or 1 and 5 in the control register will never +be set at the same time. All the above functions are mandatory to implement for a pinmux driver. @@ -742,18 +699,18 @@ Pin control interaction with the GPIO subsystem =============================================== Note that the following implies that the use case is to use a certain pin -from the Linux kernel using the API in <linux/gpio.h> with gpio_request() +from the Linux kernel using the API in <linux/gpio/consumer.h> with gpiod_get() and similar functions. There are cases where you may be using something that your datasheet calls "GPIO mode", but actually is just an electrical configuration for a certain device. See the section below named -"GPIO mode pitfalls" for more details on this scenario. +`GPIO mode pitfalls`_ for more details on this scenario. The public pinmux API contains two functions named pinctrl_gpio_request() and pinctrl_gpio_free(). These two functions shall *ONLY* be called from -gpiolib-based drivers as part of their gpio_request() and -gpio_free() semantics. Likewise the pinctrl_gpio_direction_[input|output] -shall only be called from within respective gpio_direction_[input|output] -gpiolib implementation. +gpiolib-based drivers as part of their .request() and .free() semantics. +Likewise the pinctrl_gpio_direction_input()/pinctrl_gpio_direction_output() +shall only be called from within respective .direction_input() / +.direction_output() gpiolib implementation. NOTE that platforms and individual drivers shall *NOT* request GPIO pins to be controlled e.g. muxed in. Instead, implement a proper gpiolib driver and have @@ -794,7 +751,7 @@ is taken to mean different things than what the kernel does, the developer may be confused by a datasheet talking about a pin being possible to set into "GPIO mode". It appears that what hardware engineers mean with "GPIO mode" is not necessarily the use case that is implied in the kernel -interface <linux/gpio.h>: a pin that you grab from kernel code and then +interface <linux/gpio/consumer.h>: a pin that you grab from kernel code and then either listen for input or drive high/low to assert/deassert some external line. @@ -805,9 +762,10 @@ for a device. The GPIO portions of a pin and its relation to a certain pin controller configuration and muxing logic can be constructed in several ways. Here -are two examples:: +are two examples. + +Example **(A)**:: - (A) pin config logic regs | +- SPI @@ -836,9 +794,7 @@ simultaneous access to the same pin from GPIO and pin multiplexing consumers on hardware of this type. The pinctrl driver should set this flag accordingly. -:: - - (B) +Example **(B)**:: pin config logic regs @@ -899,13 +855,13 @@ If you make a 1-to-1 map to the GPIO subsystem for this pin, you may start to think that you need to come up with something really complex, that the pin shall be used for UART TX and GPIO at the same time, that you will grab a pin control handle and set it to a certain state to enable UART TX to be -muxed in, then twist it over to GPIO mode and use gpio_direction_output() +muxed in, then twist it over to GPIO mode and use gpiod_direction_output() to drive it low during sleep, then mux it over to UART TX again when you -wake up and maybe even gpio_request/gpio_free as part of this cycle. This +wake up and maybe even gpiod_get()/gpiod_put() as part of this cycle. This all gets very complicated. The solution is to not think that what the datasheet calls "GPIO mode" -has to be handled by the <linux/gpio.h> interface. Instead view this as +has to be handled by the <linux/gpio/consumer.h> interface. Instead view this as a certain pin config setting. Look in e.g. <linux/pinctrl/pinconf-generic.h> and you find this in the documentation: @@ -915,7 +871,9 @@ and you find this in the documentation: So it is perfectly possible to push a pin into "GPIO mode" and drive the line low as part of the usual pin control map. So for example your UART -driver may look like this:: +driver may look like this: + +.. code-block:: c #include <linux/pinctrl/consumer.h> @@ -928,13 +886,13 @@ driver may look like this:: /* Normal mode */ retval = pinctrl_select_state(pinctrl, pins_default); + /* Sleep mode */ retval = pinctrl_select_state(pinctrl, pins_sleep); And your machine configuration may look like this: --------------------------------------------------- -:: +.. code-block:: c static unsigned long uart_default_mode[] = { PIN_CONF_PACKED(PIN_CONFIG_DRIVE_PUSH_PULL, 0), @@ -946,16 +904,17 @@ And your machine configuration may look like this: static struct pinctrl_map pinmap[] __initdata = { PIN_MAP_MUX_GROUP("uart", PINCTRL_STATE_DEFAULT, "pinctrl-foo", - "u0_group", "u0"), + "u0_group", "u0"), PIN_MAP_CONFIGS_PIN("uart", PINCTRL_STATE_DEFAULT, "pinctrl-foo", - "UART_TX_PIN", uart_default_mode), + "UART_TX_PIN", uart_default_mode), PIN_MAP_MUX_GROUP("uart", PINCTRL_STATE_SLEEP, "pinctrl-foo", - "u0_group", "gpio-mode"), + "u0_group", "gpio-mode"), PIN_MAP_CONFIGS_PIN("uart", PINCTRL_STATE_SLEEP, "pinctrl-foo", - "UART_TX_PIN", uart_sleep_mode), + "UART_TX_PIN", uart_sleep_mode), }; - foo_init(void) { + foo_init(void) + { pinctrl_register_mappings(pinmap, ARRAY_SIZE(pinmap)); } @@ -995,7 +954,9 @@ part of this. A pin controller configuration for a machine looks pretty much like a simple regulator configuration, so for the example array above we want to enable i2c -and spi on the second function mapping:: +and spi on the second function mapping: + +.. code-block:: c #include <linux/pinctrl/machine.h> @@ -1030,13 +991,17 @@ must match a function provided by the pinmux driver handling this pin range. As you can see we may have several pin controllers on the system and thus we need to specify which one of them contains the functions we wish to map. -You register this pinmux mapping to the pinmux subsystem by simply:: +You register this pinmux mapping to the pinmux subsystem by simply: + +.. code-block:: c ret = pinctrl_register_mappings(mapping, ARRAY_SIZE(mapping)); Since the above construct is pretty common there is a helper macro to make it even more compact which assumes you want to use pinctrl-foo and position -0 for mapping, for example:: +0 for mapping, for example: + +.. code-block:: c static struct pinctrl_map mapping[] __initdata = { PIN_MAP_MUX_GROUP("foo-i2c.o", PINCTRL_STATE_DEFAULT, @@ -1046,7 +1011,9 @@ it even more compact which assumes you want to use pinctrl-foo and position The mapping table may also contain pin configuration entries. It's common for each pin/group to have a number of configuration entries that affect it, so the table entries for configuration reference an array of config parameters -and values. An example using the convenience macros is shown below:: +and values. An example using the convenience macros is shown below: + +.. code-block:: c static unsigned long i2c_grp_configs[] = { FOO_PIN_DRIVEN, @@ -1074,7 +1041,9 @@ named states. When running on hardware that doesn't need any pin controller configuration, the mapping table must still contain those named states, in order to explicitly indicate that the states were provided and intended to be empty. Table entry macro PIN_MAP_DUMMY_STATE serves the purpose of defining -a named state without causing any pin controller to be programmed:: +a named state without causing any pin controller to be programmed: + +.. code-block:: c static struct pinctrl_map mapping[] __initdata = { PIN_MAP_DUMMY_STATE("foo-i2c.0", PINCTRL_STATE_DEFAULT), @@ -1085,7 +1054,9 @@ Complex mappings ================ As it is possible to map a function to different groups of pins an optional -.group can be specified like this:: +.group can be specified like this: + +.. code-block:: c ... { @@ -1107,13 +1078,15 @@ As it is possible to map a function to different groups of pins an optional ... This example mapping is used to switch between two positions for spi0 at -runtime, as described further below under the heading "Runtime pinmuxing". +runtime, as described further below under the heading `Runtime pinmuxing`_. Further it is possible for one named state to affect the muxing of several groups of pins, say for example in the mmc0 example above, where you can additively expand the mmc0 bus from 2 to 4 to 8 pins. If we want to use all -three groups for a total of 2+2+4 = 8 pins (for an 8-bit MMC bus as is the -case), we define a mapping like this:: +three groups for a total of 2 + 2 + 4 = 8 pins (for an 8-bit MMC bus as is the +case), we define a mapping like this: + +.. code-block:: c ... { @@ -1167,13 +1140,17 @@ case), we define a mapping like this:: ... The result of grabbing this mapping from the device with something like -this (see next paragraph):: +this (see next paragraph): + +.. code-block:: c p = devm_pinctrl_get(dev); s = pinctrl_lookup_state(p, "8bit"); ret = pinctrl_select_state(p, s); -or more simply:: +or more simply: + +.. code-block:: c p = devm_pinctrl_get_select(dev, "8bit"); @@ -1211,7 +1188,9 @@ PINCTRL_STATE_SLEEP at runtime, re-biasing or even re-muxing pins to save current in sleep mode. A driver may request a certain control state to be activated, usually just the -default state like this:: +default state like this: + +.. code-block:: c #include <linux/pinctrl/consumer.h> @@ -1285,7 +1264,7 @@ The semantics of the pinctrl APIs are: Usually the pin control core handled the get/put pair and call out to the device drivers bookkeeping operations, like checking available functions and -the associated pins, whereas select_state pass on to the pin controller +the associated pins, whereas pinctrl_select_state() pass on to the pin controller driver which takes care of activating and/or deactivating the mux setting by quickly poking some registers. @@ -1305,18 +1284,20 @@ Drivers needing both pin control and GPIOs Again, it is discouraged to let drivers lookup and select pin control states themselves, but again sometimes this is unavoidable. -So say that your driver is fetching its resources like this:: +So say that your driver is fetching its resources like this: + +.. code-block:: c #include <linux/pinctrl/consumer.h> - #include <linux/gpio.h> + #include <linux/gpio/consumer.h> struct pinctrl *pinctrl; - int gpio; + struct gpio_desc *gpio; pinctrl = devm_pinctrl_get_select_default(&dev); - gpio = devm_gpio_request(&dev, 14, "foo"); + gpio = devm_gpiod_get(&dev, "foo"); -Here we first request a certain pin state and then request GPIO 14 to be +Here we first request a certain pin state and then request GPIO "foo" to be used. If you're using the subsystems orthogonally like this, you should nominally always get your pinctrl handle and select the desired pinctrl state BEFORE requesting the GPIO. This is a semantic convention to avoid @@ -1331,9 +1312,9 @@ probing, nevertheless orthogonal to the GPIO subsystem. But there are also situations where it makes sense for the GPIO subsystem to communicate directly with the pinctrl subsystem, using the latter as a back-end. This is when the GPIO driver may call out to the functions -described in the section "Pin control interaction with the GPIO subsystem" +described in the section `Pin control interaction with the GPIO subsystem`_ above. This only involves per-pin multiplexing, and will be completely -hidden behind the gpio_*() function namespace. In this case, the driver +hidden behind the gpiod_*() function namespace. In this case, the driver need not interact with the pin control subsystem at all. If a pin control driver and a GPIO driver is dealing with the same pins @@ -1349,11 +1330,13 @@ System pin control hogging Pin control map entries can be hogged by the core when the pin controller is registered. This means that the core will attempt to call pinctrl_get(), -lookup_state() and select_state() on it immediately after the pin control -device has been registered. +pinctrl_lookup_state() and pinctrl_select_state() on it immediately after +the pin control device has been registered. This occurs for mapping table entries where the client device name is equal -to the pin controller device name, and the state name is PINCTRL_STATE_DEFAULT:: +to the pin controller device name, and the state name is PINCTRL_STATE_DEFAULT: + +.. code-block:: c { .dev_name = "pinctrl-foo", @@ -1365,7 +1348,9 @@ to the pin controller device name, and the state name is PINCTRL_STATE_DEFAULT:: Since it may be common to request the core to hog a few always-applicable mux settings on the primary pin controller, there is a convenience macro for -this:: +this: + +.. code-block:: c PIN_MAP_MUX_GROUP_HOG_DEFAULT("pinctrl-foo", NULL /* group */, "power_func") @@ -1385,7 +1370,9 @@ function, but with different named in the mapping as described under This snippet first initializes a state object for both groups (in foo_probe()), then muxes the function in the pins defined by group A, and finally muxes it in -on the pins defined by group B:: +on the pins defined by group B: + +.. code-block:: c #include <linux/pinctrl/consumer.h> @@ -1413,14 +1400,14 @@ on the pins defined by group B:: /* Enable on position A */ ret = pinctrl_select_state(p, s1); if (ret < 0) - ... + ... ... /* Enable on position B */ ret = pinctrl_select_state(p, s2); if (ret < 0) - ... + ... ... } @@ -1432,6 +1419,7 @@ can be used by different functions at different times on a running system. Debugfs files ============= + These files are created in ``/sys/kernel/debug/pinctrl``: - ``pinctrl-devices``: prints each pin controller device along with columns to @@ -1440,7 +1428,7 @@ These files are created in ``/sys/kernel/debug/pinctrl``: - ``pinctrl-handles``: prints each configured pin controller handle and the corresponding pinmux maps -- ``pinctrl-maps``: print all pinctrl maps +- ``pinctrl-maps``: prints all pinctrl maps A sub-directory is created inside of ``/sys/kernel/debug/pinctrl`` for each pin controller device containing these files: @@ -1448,20 +1436,22 @@ controller device containing these files: - ``pins``: prints a line for each pin registered on the pin controller. The pinctrl driver may add additional information such as register contents. -- ``gpio-ranges``: print ranges that map gpio lines to pins on the controller +- ``gpio-ranges``: prints ranges that map gpio lines to pins on the controller -- ``pingroups``: print all pin groups registered on the pin controller +- ``pingroups``: prints all pin groups registered on the pin controller -- ``pinconf-pins``: print pin config settings for each pin +- ``pinconf-pins``: prints pin config settings for each pin -- ``pinconf-groups``: print pin config settings per pin group +- ``pinconf-groups``: prints pin config settings per pin group -- ``pinmux-functions``: print each pin function along with the pin groups that +- ``pinmux-functions``: prints each pin function along with the pin groups that map to the pin function -- ``pinmux-pins``: iterate through all pins and print mux owner, gpio owner +- ``pinmux-pins``: iterates through all pins and prints mux owner, gpio owner and if the pin is a hog -- ``pinmux-select``: write to this file to activate a pin function for a group:: +- ``pinmux-select``: write to this file to activate a pin function for a group: + + .. code-block:: sh echo "<group-name function-name>" > pinmux-select
Proofreading and updating the documentation accordingly, i.e. fixed: - ambiguity of foo_set_mux() implementation and explanations - semantics in some of the examples, e.g. _probe() --> _init() - references to the callbacks to make them start with dot - references to the legacy API by replacing them with newer one - indentation in some of the examples - double words or phrases updated: - unsigned --> unsigned int in some of the examples - use struct pingroup and PINCTRL_PINGROUP() in some of the examples - use struct pinfunction and PINCTRL_PINFUNCTION() in some of the examples and enabled: - syntax highlighting for the examples in the programming languages - chapter references Yet to clarify: - "gpioN" menton for the default function when requesting GPIO Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> --- It takes quite a bit of time for me to accomplish that. Anyway, there is still open question (see commit message above) and even though this needs checking and reading the rendered (as HTML and/or PDF) file for formatting / spelling / semantical / logical / etc. issues. Reviewing the patch without that makes a little sense, since it doesn't give the context. Also note, it includes some changes that rely on what I have in my repo if this is going to be Reviewed/Acked I would like to push it to my tree. Documentation/driver-api/pin-control.rst | 412 +++++++++++------------ 1 file changed, 201 insertions(+), 211 deletions(-)