| Message ID | 1397463709-19405-1-git-send-email-p.zabel@pengutronix.de |
|---|---|
| State | Superseded, archived |
| Headers | show |
> This adds support for GPIO controlled reset pins on peripheral ICs to the reset > controller framework. Currently there is no support for specifying a delay > between assertion and de-assertion of the reset signal, so this has to be > handled by the drivers. Lots of GPIO controllers are doing posted writes to the fabric so surely your delay will be wrong ? Alan -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Alan, Am Montag, den 14.04.2014, 11:57 +0100 schrieb One Thousand Gnomes: > > This adds support for GPIO controlled reset pins on peripheral ICs to the reset > > controller framework. Currently there is no support for specifying a delay > > between assertion and de-assertion of the reset signal, so this has to be > > handled by the drivers. > > Lots of GPIO controllers are doing posted writes to the fabric so surely > your delay will be wrong ? I haven't seen hardware yet where this is an issue, but it's a valid point. I can also imagine boards where the GPIO is connected to some board specific timed reset logic or where the reset length has to be altered just due to capacitance. regards Philipp -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Apr 14, 2014 at 10:21:48AM +0200, Philipp Zabel wrote: > This patch adds documentation clarifying the reset GPIO bindings most > commonly in use (reset-gpios and <name>-reset-gpios properties). > > Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de> > --- > Documentation/devicetree/bindings/reset/reset.txt | 26 +++++++++++++++++++++-- > 1 file changed, 24 insertions(+), 2 deletions(-) > > diff --git a/Documentation/devicetree/bindings/reset/reset.txt b/Documentation/devicetree/bindings/reset/reset.txt > index 31db6ff..51f9e35 100644 > --- a/Documentation/devicetree/bindings/reset/reset.txt > +++ b/Documentation/devicetree/bindings/reset/reset.txt > @@ -2,8 +2,8 @@ > > This binding is intended to represent the hardware reset signals present > internally in most IC (SoC, FPGA, ...) designs. Reset signals for whole > -standalone chips are most likely better represented as GPIOs, although there > -are likely to be exceptions to this rule. > +standalone chips are most likely better represented as GPIOs, ideally using a > +common scheme as described below. > > Hardware blocks typically receive a reset signal. This signal is generated by > a reset provider (e.g. power management or clock module) and received by a > @@ -56,6 +56,20 @@ reset-names: List of reset signal name strings sorted in the same order as > the resets property. Consumers drivers will use reset-names to > match reset signal names with reset specifiers. > > += GPIO Reset consumers = > + > +For the common case of reset lines controlled by GPIOs, the GPIO binding > +documented in devicetree/bindings/gpio/gpio.txt should be used: > + > +Required properties: > +reset-gpios or Reset GPIO using standard GPIO bindings, > +<name>-reset-gpios: optionally named to specify the reset line > + > +Optional properties: > +reset-boot-asserted or Boolean. If set, the corresponding reset is > +<name>-reset-boot-asserted: initially asserted and should be kept that way > + until released by the driver. > + I still feel like we should really treat gpios like just another reset controller, ie. using the resets property. I understand that you chose this pattern to be pretty much compatible with what have been done so fare, bu I don't see how to fulfill that goal completely, since most of the devices are actually using reset-gpios, but some are using other names too (including reset-gpio). So if we can't be fully backward compatible, I don't see the benefit of being inconsistent with how reset controllers are used in general, and more globally on how gpios are tied for regulators for example. That would also make reset-gpio a regular reset driver, instead of adding logic to the core itself to handle this special case. Maxime
Hi Maxime, Am Donnerstag, den 17.04.2014, 13:58 +0200 schrieb Maxime Ripard: > I still feel like we should really treat gpios like just another reset > controller, ie. using the resets property. I now feel like we really shouldn't. If we do anything but use the generic gpio bindings for reset gpios, we might force every OS or bootloader using the device tree to implement some kind of reset controller framework, even for hardware that only has gpio resets. > I understand that you chose this pattern to be pretty much compatible > with what have been done so fare, bu I don't see how to fulfill that > goal completely, since most of the devices are actually using > reset-gpios, but some are using other names too (including > reset-gpio). Yes, that is a problem that applies to all gpios, not only to reset gpios, though. > So if we can't be fully backward compatible, I don't see the benefit > of being inconsistent with how reset controllers are used in general, See above. > and more globally on how gpios are tied for regulators for example. Reset controllers are rather more similar to gpio or interrupt controllers. Those also have a number of entities per device node, as opposed to regulators. > That would also make reset-gpio a regular reset driver, instead of > adding logic to the core itself to handle this special case. Which is what I initially tried and moved away from. regards Philipp -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Apr 30, 2014 at 10:54:22AM +0200, Philipp Zabel wrote: > Hi Maxime, > > Am Donnerstag, den 17.04.2014, 13:58 +0200 schrieb Maxime Ripard: > > I still feel like we should really treat gpios like just another reset > > controller, ie. using the resets property. > > I now feel like we really shouldn't. If we do anything but use the > generic gpio bindings for reset gpios, we might force every OS or > bootloader using the device tree to implement some kind of reset > controller framework, even for hardware that only has gpio resets. Well, we pretty much introduced that requirement already whenever we got this framework in the first place. You can now expect pretty much anything, even a CPU or a timer to have a reset property, so you have to handle them anyway. So I'd be much more in favor of consistency both with other frameworks and within the reset framework itself. > > I understand that you chose this pattern to be pretty much compatible > > with what have been done so fare, bu I don't see how to fulfill that > > goal completely, since most of the devices are actually using > > reset-gpios, but some are using other names too (including > > reset-gpio). > > Yes, that is a problem that applies to all gpios, not only to reset > gpios, though. Indeed, but you're the only one I can think of that have tried to factor the gpio handling in the framework after the facts. All the other either have no standards and let the driver deal with it, or have explicitly asked for a given property name. > > So if we can't be fully backward compatible, I don't see the benefit > > of being inconsistent with how reset controllers are used in general, > > See above. > > > and more globally on how gpios are tied for regulators for example. > > Reset controllers are rather more similar to gpio or interrupt > controllers. Those also have a number of entities per device node, > as opposed to regulators. Well, that depends on the bindings actually. The fact that the reset controller can handle several reset lines is dependent of the controller itself. And I believe we can say pretty much the same about the regulators. > > That would also make reset-gpio a regular reset driver, instead of > > adding logic to the core itself to handle this special case. > > Which is what I initially tried and moved away from. Yeah, I know. Overall, I'd very much like the DT maintainers to step in on this. Especially after the discussion we had again yesterday about the stable DT bindings things. Stable DT bindings only works if the DT maintainers can do some arbitration in this case. Mark? Ping?
diff --git a/Documentation/devicetree/bindings/reset/reset.txt b/Documentation/devicetree/bindings/reset/reset.txt index 31db6ff..51f9e35 100644 --- a/Documentation/devicetree/bindings/reset/reset.txt +++ b/Documentation/devicetree/bindings/reset/reset.txt @@ -2,8 +2,8 @@ This binding is intended to represent the hardware reset signals present internally in most IC (SoC, FPGA, ...) designs. Reset signals for whole -standalone chips are most likely better represented as GPIOs, although there -are likely to be exceptions to this rule. +standalone chips are most likely better represented as GPIOs, ideally using a +common scheme as described below. Hardware blocks typically receive a reset signal. This signal is generated by a reset provider (e.g. power management or clock module) and received by a @@ -56,6 +56,20 @@ reset-names: List of reset signal name strings sorted in the same order as the resets property. Consumers drivers will use reset-names to match reset signal names with reset specifiers. += GPIO Reset consumers = + +For the common case of reset lines controlled by GPIOs, the GPIO binding +documented in devicetree/bindings/gpio/gpio.txt should be used: + +Required properties: +reset-gpios or Reset GPIO using standard GPIO bindings, +<name>-reset-gpios: optionally named to specify the reset line + +Optional properties: +reset-boot-asserted or Boolean. If set, the corresponding reset is +<name>-reset-boot-asserted: initially asserted and should be kept that way + until released by the driver. + For example: device { @@ -65,6 +79,14 @@ For example: This represents a device with a single reset signal named "reset". + device2 { + reset-gpios = <&gpio3 15 GPIO_ACTIVE_LOW>; + reset-boot-asserted; + }; + +This represents a device with a single reset signal, controlled +by an active-low GPIO, which is initally kept in reset. + bus { resets = <&rst 10> <&rst 11> <&rst 12> <&rst 11>; reset-names = "i2s1", "i2s2", "dma", "mixer";
This patch adds documentation clarifying the reset GPIO bindings most commonly in use (reset-gpios and <name>-reset-gpios properties). Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de> --- Documentation/devicetree/bindings/reset/reset.txt | 26 +++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-)