| Message ID | 1434458208-30600-1-git-send-email-geert+renesas@glider.be |
|---|---|
| State | New |
| Headers | show |
Hi Geert, On Tue, Jun 16, 2015 at 02:36:48PM +0200, Geert Uytterhoeven wrote: > If a GPIO driver uses gpiochip_add_pin_range() (which is usually the > case for GPIO/PFC combos), the GPIO hogging mechanism configured from DT > doesn't work: > > requesting hog GPIO lcd0 (chip r8a7740_pfc, offset 176) failed > > The actual error code is -517 == -EPROBE_DEFER. > > The problem is that PFC+GPIO registration is handled in multiple steps: > 1. pinctrl_register(), > 2. gpiochip_add(), > 3. gpiochip_add_pin_range(). > > Configuration of the hogs is handled in gpiochip_add(): > > gpiochip_add > of_gpiochip_add > of_gpiochip_scan_hogs > gpiod_hog > gpiochip_request_own_desc > __gpiod_request > chip->request > pinctrl_request_gpio > pinctrl_get_device_gpio_range > > However, at this point the GPIO controller hasn't been added to > pinctrldev_list yet, so the range can't be found, and the operation fails > with -EPROBE_DEFER. > > - Exchanging the order of the calls to gpiochip_add() and > gpiochip_add_pin_range() is not an option, as the latter depends on > initialization done by the former. > - Just moving the call of of_gpiochip_scan_hogs() from gpiochip_add() > to gpiochip_add_pin_range() is also not an option, as the latter is > optional, and thus not used by all drivers. > > Hence if of_gpiochip_scan_hogs() fails with -EPROBE_DEFER, call it > again every time the pin range is changed, until it succeeded. > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > Questions: > - Is there a better solution to handle this? > > - Should the pin ranges be configured by passing an array of data to > gpiochip_add() instead of having calls to gpiochip_add_pin_range()? > That would require changing all drivers. > > - What happens if you have multiple hogs in multiple ranges? > The first hog(s) may be configured multiple times. Is that a problem? > > - In one of the threads that discussed the GPIO hogging mechanism, Maxime > Ripard said: "Our pinctrl driver is also our GPIO driver, so they both > share the same node." > Maxime: Did you try GPIO hogging? Did it work? > If yes, which driver are you using? What's different compared to sh-pfc? > If no, did you get it to work? I'm using pinctrl-sunxi, and no, I haven't tried it yet, so it probably have the issue you reported :) Maxime
On Tue, Jun 16, 2015 at 9:36 PM, Geert Uytterhoeven <geert+renesas@glider.be> wrote: > If a GPIO driver uses gpiochip_add_pin_range() (which is usually the > case for GPIO/PFC combos), the GPIO hogging mechanism configured from DT > doesn't work: > > requesting hog GPIO lcd0 (chip r8a7740_pfc, offset 176) failed > > The actual error code is -517 == -EPROBE_DEFER. > > The problem is that PFC+GPIO registration is handled in multiple steps: > 1. pinctrl_register(), > 2. gpiochip_add(), > 3. gpiochip_add_pin_range(). > > Configuration of the hogs is handled in gpiochip_add(): > > gpiochip_add > of_gpiochip_add > of_gpiochip_scan_hogs > gpiod_hog > gpiochip_request_own_desc > __gpiod_request > chip->request > pinctrl_request_gpio > pinctrl_get_device_gpio_range > > However, at this point the GPIO controller hasn't been added to > pinctrldev_list yet, so the range can't be found, and the operation fails > with -EPROBE_DEFER. > > - Exchanging the order of the calls to gpiochip_add() and > gpiochip_add_pin_range() is not an option, as the latter depends on > initialization done by the former. > - Just moving the call of of_gpiochip_scan_hogs() from gpiochip_add() > to gpiochip_add_pin_range() is also not an option, as the latter is > optional, and thus not used by all drivers. > > Hence if of_gpiochip_scan_hogs() fails with -EPROBE_DEFER, call it > again every time the pin range is changed, until it succeeded. > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > Questions: > - Is there a better solution to handle this? I do not understand the issue well enough to propose a better solution, but I really hope there is one. This turns GPIO into a slightly bigger yarn mess that what it already is and does not help understanding how probing is performed. Yielding in the middle of adding hogs and re-trying later sounds like a recipe for issues like hogs being added several times. So I am not really fond of this, to be honest. The GPIO hogging mechanism is still quite new, so there is certainly a way to fix such issues by addressing the fundamental cause instead of duct taping it? > > - Should the pin ranges be configured by passing an array of data to > gpiochip_add() instead of having calls to gpiochip_add_pin_range()? > That would require changing all drivers. > > - What happens if you have multiple hogs in multiple ranges? > The first hog(s) may be configured multiple times. Is that a problem? > > - In one of the threads that discussed the GPIO hogging mechanism, Maxime > Ripard said: "Our pinctrl driver is also our GPIO driver, so they both > share the same node." > Maxime: Did you try GPIO hogging? Did it work? > If yes, which driver are you using? What's different compared to sh-pfc? > If no, did you get it to work? > > Thanks! > --- > drivers/gpio/gpiolib-of.c | 21 +++++++++++++++++---- > drivers/gpio/gpiolib.c | 1 + > include/linux/gpio/driver.h | 1 + > include/linux/of_gpio.h | 2 ++ > 4 files changed, 21 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c > index 9a0ec48a47375d18..90dd02b19f75c27c 100644 > --- a/drivers/gpio/gpiolib-of.c > +++ b/drivers/gpio/gpiolib-of.c > @@ -205,13 +205,14 @@ static struct gpio_desc *of_get_gpio_hog(struct device_node *np, > * This is only used by of_gpiochip_add to request/set GPIO initial > * configuration. > */ > -static void of_gpiochip_scan_hogs(struct gpio_chip *chip) > +static int of_gpiochip_scan_hogs(struct gpio_chip *chip) > { > struct gpio_desc *desc = NULL; > struct device_node *np; > const char *name; > enum gpio_lookup_flags lflags; > enum gpiod_flags dflags; > + int error; > > for_each_child_of_node(chip->of_node, np) { > if (!of_property_read_bool(np, "gpio-hog")) > @@ -221,9 +222,12 @@ static void of_gpiochip_scan_hogs(struct gpio_chip *chip) > if (IS_ERR(desc)) > continue; > > - if (gpiod_hog(desc, name, lflags, dflags)) > - continue; > + error = gpiod_hog(desc, name, lflags, dflags); > + if (error == -EPROBE_DEFER) > + return error; > } > + > + return 0; > } > > /** > @@ -416,8 +420,17 @@ static void of_gpiochip_add_pin_range(struct gpio_chip *chip) > } > } > > +void of_gpiochip_pin_range_changed(struct gpio_chip *chip) > +{ > + if (chip->hog_error) { > + /* Retry */ > + chip->hog_error = of_gpiochip_scan_hogs(chip); > + } > +} > + > #else > static void of_gpiochip_add_pin_range(struct gpio_chip *chip) {} > +void of_gpiochip_pin_range_changed(struct gpio_chip *chip) {} > #endif > > void of_gpiochip_add(struct gpio_chip *chip) > @@ -436,7 +449,7 @@ void of_gpiochip_add(struct gpio_chip *chip) > of_gpiochip_add_pin_range(chip); > of_node_get(chip->of_node); > > - of_gpiochip_scan_hogs(chip); > + chip->hog_error = of_gpiochip_scan_hogs(chip); > } > > void of_gpiochip_remove(struct gpio_chip *chip) > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c > index 957ede5664cfe168..b0fe7a459d8835bb 100644 > --- a/drivers/gpio/gpiolib.c > +++ b/drivers/gpio/gpiolib.c > @@ -759,6 +759,7 @@ int gpiochip_add_pin_range(struct gpio_chip *chip, const char *pinctl_name, > > list_add_tail(&pin_range->node, &chip->pin_ranges); > > + of_gpiochip_pin_range_changed(chip); > return 0; > } > EXPORT_SYMBOL_GPL(gpiochip_add_pin_range); > diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h > index c8393cd4d44f2d87..9396b68dced2c5b1 100644 > --- a/include/linux/gpio/driver.h > +++ b/include/linux/gpio/driver.h > @@ -146,6 +146,7 @@ struct gpio_chip { > * corresponding pins for gpio usage. > */ > struct list_head pin_ranges; > + int hog_error; > #endif > }; > > diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h > index 69dbe312b11b23f6..34421f17f4712d0b 100644 > --- a/include/linux/of_gpio.h > +++ b/include/linux/of_gpio.h > @@ -54,6 +54,7 @@ extern int of_mm_gpiochip_add(struct device_node *np, > struct of_mm_gpio_chip *mm_gc); > extern void of_mm_gpiochip_remove(struct of_mm_gpio_chip *mm_gc); > > +extern void of_gpiochip_pin_range_changed(struct gpio_chip *chip); > extern void of_gpiochip_add(struct gpio_chip *gc); > extern void of_gpiochip_remove(struct gpio_chip *gc); > extern int of_gpio_simple_xlate(struct gpio_chip *gc, > @@ -76,6 +77,7 @@ static inline int of_gpio_simple_xlate(struct gpio_chip *gc, > return -ENOSYS; > } > > +static inline void of_gpiochip_pin_range_changed(struct gpio_chip *chip) { } > static inline void of_gpiochip_add(struct gpio_chip *gc) { } > static inline void of_gpiochip_remove(struct gpio_chip *gc) { } > > -- > 1.9.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
Hi Alex, On Sun, Jun 21, 2015 at 9:21 AM, Alexandre Courbot <gnurou@gmail.com> wrote: > On Tue, Jun 16, 2015 at 9:36 PM, Geert Uytterhoeven > <geert+renesas@glider.be> wrote: >> If a GPIO driver uses gpiochip_add_pin_range() (which is usually the >> case for GPIO/PFC combos), the GPIO hogging mechanism configured from DT >> doesn't work: >> >> requesting hog GPIO lcd0 (chip r8a7740_pfc, offset 176) failed >> >> The actual error code is -517 == -EPROBE_DEFER. >> >> The problem is that PFC+GPIO registration is handled in multiple steps: >> 1. pinctrl_register(), >> 2. gpiochip_add(), >> 3. gpiochip_add_pin_range(). >> >> Configuration of the hogs is handled in gpiochip_add(): >> >> gpiochip_add >> of_gpiochip_add >> of_gpiochip_scan_hogs >> gpiod_hog >> gpiochip_request_own_desc >> __gpiod_request >> chip->request >> pinctrl_request_gpio >> pinctrl_get_device_gpio_range >> >> However, at this point the GPIO controller hasn't been added to >> pinctrldev_list yet, so the range can't be found, and the operation fails >> with -EPROBE_DEFER. >> >> - Exchanging the order of the calls to gpiochip_add() and >> gpiochip_add_pin_range() is not an option, as the latter depends on >> initialization done by the former. >> - Just moving the call of of_gpiochip_scan_hogs() from gpiochip_add() >> to gpiochip_add_pin_range() is also not an option, as the latter is >> optional, and thus not used by all drivers. >> >> Hence if of_gpiochip_scan_hogs() fails with -EPROBE_DEFER, call it >> again every time the pin range is changed, until it succeeded. >> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> >> --- >> Questions: >> - Is there a better solution to handle this? > > I do not understand the issue well enough to propose a better > solution, but I really hope there is one. This turns GPIO into a > slightly bigger yarn mess that what it already is and does not help > understanding how probing is performed. Yielding in the middle of > adding hogs and re-trying later sounds like a recipe for issues like > hogs being added several times. > > So I am not really fond of this, to be honest. The GPIO hogging > mechanism is still quite new, so there is certainly a way to fix such > issues by addressing the fundamental cause instead of duct taping it? Sure, I'm all for fixing this properly, hence the "RFC" and my questions. I also don't understand how this interacts with non-PFC drivers calling gpiochip_add_pin_range(): - gpio-em, but only for legacy platform devices, which are no longer used (I will remove the legacy support), - gpio-rcar, but only for legacy platform devices, which is used on R-Car Gen1 only until -legacy is removed, - gpiolib-of, which handles this for the bulk of modern GPIO drivers using the "gpio-ranges" and "gpio-ranges-group-names" properties in DT. When I noticed the failure on r8a7740/armadillo (sh-pfc provides both pfc and gpio), I tried GPIO hogging on r8a7791/koelsch (sh-pfc provides pfc only, gpio-rcar provides gpio, "gpio-ranges" is in DT), and there it worked fine without my patch. Thanks! >> - Should the pin ranges be configured by passing an array of data to >> gpiochip_add() instead of having calls to gpiochip_add_pin_range()? >> That would require changing all drivers. >> >> - What happens if you have multiple hogs in multiple ranges? >> The first hog(s) may be configured multiple times. Is that a problem? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
On Sun, Jun 21, 2015 at 10:52 AM, Geert Uytterhoeven <geert@linux-m68k.org> wrote: > On Sun, Jun 21, 2015 at 9:21 AM, Alexandre Courbot <gnurou@gmail.com> wrote: >> On Tue, Jun 16, 2015 at 9:36 PM, Geert Uytterhoeven >> <geert+renesas@glider.be> wrote: >>> If a GPIO driver uses gpiochip_add_pin_range() (which is usually the >>> case for GPIO/PFC combos), the GPIO hogging mechanism configured from DT >>> doesn't work: >>> >>> requesting hog GPIO lcd0 (chip r8a7740_pfc, offset 176) failed >>> >>> The actual error code is -517 == -EPROBE_DEFER. >>> >>> The problem is that PFC+GPIO registration is handled in multiple steps: >>> 1. pinctrl_register(), >>> 2. gpiochip_add(), >>> 3. gpiochip_add_pin_range(). >>> >>> Configuration of the hogs is handled in gpiochip_add(): >>> >>> gpiochip_add >>> of_gpiochip_add >>> of_gpiochip_scan_hogs >>> gpiod_hog >>> gpiochip_request_own_desc >>> __gpiod_request >>> chip->request >>> pinctrl_request_gpio >>> pinctrl_get_device_gpio_range >>> >>> However, at this point the GPIO controller hasn't been added to >>> pinctrldev_list yet, so the range can't be found, and the operation fails >>> with -EPROBE_DEFER. >>> >>> - Exchanging the order of the calls to gpiochip_add() and >>> gpiochip_add_pin_range() is not an option, as the latter depends on >>> initialization done by the former. >>> - Just moving the call of of_gpiochip_scan_hogs() from gpiochip_add() >>> to gpiochip_add_pin_range() is also not an option, as the latter is >>> optional, and thus not used by all drivers. >>> >>> Hence if of_gpiochip_scan_hogs() fails with -EPROBE_DEFER, call it >>> again every time the pin range is changed, until it succeeded. >>> >>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> >>> --- >>> Questions: >>> - Is there a better solution to handle this? >> >> I do not understand the issue well enough to propose a better >> solution, but I really hope there is one. This turns GPIO into a >> slightly bigger yarn mess that what it already is and does not help >> understanding how probing is performed. Yielding in the middle of >> adding hogs and re-trying later sounds like a recipe for issues like >> hogs being added several times. >> >> So I am not really fond of this, to be honest. The GPIO hogging >> mechanism is still quite new, so there is certainly a way to fix such >> issues by addressing the fundamental cause instead of duct taping it? > > Sure, I'm all for fixing this properly, hence the "RFC" and my questions. > > I also don't understand how this interacts with non-PFC drivers calling > gpiochip_add_pin_range(): > - gpio-em, but only for legacy platform devices, which are no longer used > (I will remove the legacy support), > - gpio-rcar, but only for legacy platform devices, which is used on R-Car > Gen1 only until -legacy is removed, > - gpiolib-of, which handles this for the bulk of modern GPIO drivers using > the "gpio-ranges" and "gpio-ranges-group-names" properties in DT. > > When I noticed the failure on r8a7740/armadillo (sh-pfc provides both pfc > and gpio), I tried GPIO hogging on r8a7791/koelsch (sh-pfc provides pfc > only, gpio-rcar provides gpio, "gpio-ranges" is in DT), and there it worked > fine without my patch. "gpio-ranges" and gpiochip_add_pin_range() turned out to be the solution to the problem: on DT platforms, parsing "gpio-ranges" is doing from of_gpiochip_add(), which is called from gpiochip_add(). Hence the ranges are set up from DT just before the hogs are handled: void of_gpiochip_add(struct gpio_chip *chip) { ... of_gpiochip_add_pin_range(chip); ... of_gpiochip_scan_hogs(chip); } Sticking a "gpio-ranges" in arch/arm/boot/dts/r8a7740.dtsi: @@ -288,12 +288,13 @@ pfc: pfc@e6050000 { compatible = "renesas,pfc-r8a7740"; reg = <0xe6050000 0x8000>, <0xe605800c 0x20>; gpio-controller; #gpio-cells = <2>; + gpio-ranges = <&pfc 0 0 212>; interrupts-extended = <&irqpin0 0 0>, <&irqpin0 1 0>, <&irqpin0 2 0>, <&irqpin0 3 0>, <&irqpin0 4 0>, <&irqpin0 5 0>, <&irqpin0 6 0>, <&irqpin0 7 0>, <&irqpin1 0 0>, <&irqpin1 1 0>, <&irqpin1 2 0>, <&irqpin1 3 0>, <&irqpin1 4 0>, <&irqpin1 5 0>, <&irqpin1 6 0>, <&irqpin1 7 0>, <&irqpin2 0 0>, <&irqpin2 1 0>, <&irqpin2 2 0>, <&irqpin2 3 0>, solved the problem for me. Note that "&pfc" is a reference to the gpio device node itself, as it provides both GPIO and PFC functionalities. After that, the calls to gpiochip_add_pin_range() in drivers/pinctrl/sh-pfc/gpio.c can be removed, at least for the ARM multi-platform case where GPIO is instantiated from DT (_and_ "gpio-ranges" is present --- I don't think we have to care about DT backwards compatibility for sh73a0/r8a73a4/r8a7740). Does this makes sense? I couldn't find any other in-tree DTS that has a gpio-controller with a gpio-ranges pointing to itself. All other GPIO+PFC combos lack such properties, and thus probably won't work with DT gpio-hogs. Thanks for your comments! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c index 9a0ec48a47375d18..90dd02b19f75c27c 100644 --- a/drivers/gpio/gpiolib-of.c +++ b/drivers/gpio/gpiolib-of.c @@ -205,13 +205,14 @@ static struct gpio_desc *of_get_gpio_hog(struct device_node *np, * This is only used by of_gpiochip_add to request/set GPIO initial * configuration. */ -static void of_gpiochip_scan_hogs(struct gpio_chip *chip) +static int of_gpiochip_scan_hogs(struct gpio_chip *chip) { struct gpio_desc *desc = NULL; struct device_node *np; const char *name; enum gpio_lookup_flags lflags; enum gpiod_flags dflags; + int error; for_each_child_of_node(chip->of_node, np) { if (!of_property_read_bool(np, "gpio-hog")) @@ -221,9 +222,12 @@ static void of_gpiochip_scan_hogs(struct gpio_chip *chip) if (IS_ERR(desc)) continue; - if (gpiod_hog(desc, name, lflags, dflags)) - continue; + error = gpiod_hog(desc, name, lflags, dflags); + if (error == -EPROBE_DEFER) + return error; } + + return 0; } /** @@ -416,8 +420,17 @@ static void of_gpiochip_add_pin_range(struct gpio_chip *chip) } } +void of_gpiochip_pin_range_changed(struct gpio_chip *chip) +{ + if (chip->hog_error) { + /* Retry */ + chip->hog_error = of_gpiochip_scan_hogs(chip); + } +} + #else static void of_gpiochip_add_pin_range(struct gpio_chip *chip) {} +void of_gpiochip_pin_range_changed(struct gpio_chip *chip) {} #endif void of_gpiochip_add(struct gpio_chip *chip) @@ -436,7 +449,7 @@ void of_gpiochip_add(struct gpio_chip *chip) of_gpiochip_add_pin_range(chip); of_node_get(chip->of_node); - of_gpiochip_scan_hogs(chip); + chip->hog_error = of_gpiochip_scan_hogs(chip); } void of_gpiochip_remove(struct gpio_chip *chip) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 957ede5664cfe168..b0fe7a459d8835bb 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -759,6 +759,7 @@ int gpiochip_add_pin_range(struct gpio_chip *chip, const char *pinctl_name, list_add_tail(&pin_range->node, &chip->pin_ranges); + of_gpiochip_pin_range_changed(chip); return 0; } EXPORT_SYMBOL_GPL(gpiochip_add_pin_range); diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h index c8393cd4d44f2d87..9396b68dced2c5b1 100644 --- a/include/linux/gpio/driver.h +++ b/include/linux/gpio/driver.h @@ -146,6 +146,7 @@ struct gpio_chip { * corresponding pins for gpio usage. */ struct list_head pin_ranges; + int hog_error; #endif }; diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h index 69dbe312b11b23f6..34421f17f4712d0b 100644 --- a/include/linux/of_gpio.h +++ b/include/linux/of_gpio.h @@ -54,6 +54,7 @@ extern int of_mm_gpiochip_add(struct device_node *np, struct of_mm_gpio_chip *mm_gc); extern void of_mm_gpiochip_remove(struct of_mm_gpio_chip *mm_gc); +extern void of_gpiochip_pin_range_changed(struct gpio_chip *chip); extern void of_gpiochip_add(struct gpio_chip *gc); extern void of_gpiochip_remove(struct gpio_chip *gc); extern int of_gpio_simple_xlate(struct gpio_chip *gc, @@ -76,6 +77,7 @@ static inline int of_gpio_simple_xlate(struct gpio_chip *gc, return -ENOSYS; } +static inline void of_gpiochip_pin_range_changed(struct gpio_chip *chip) { } static inline void of_gpiochip_add(struct gpio_chip *gc) { } static inline void of_gpiochip_remove(struct gpio_chip *gc) { }
If a GPIO driver uses gpiochip_add_pin_range() (which is usually the case for GPIO/PFC combos), the GPIO hogging mechanism configured from DT doesn't work: requesting hog GPIO lcd0 (chip r8a7740_pfc, offset 176) failed The actual error code is -517 == -EPROBE_DEFER. The problem is that PFC+GPIO registration is handled in multiple steps: 1. pinctrl_register(), 2. gpiochip_add(), 3. gpiochip_add_pin_range(). Configuration of the hogs is handled in gpiochip_add(): gpiochip_add of_gpiochip_add of_gpiochip_scan_hogs gpiod_hog gpiochip_request_own_desc __gpiod_request chip->request pinctrl_request_gpio pinctrl_get_device_gpio_range However, at this point the GPIO controller hasn't been added to pinctrldev_list yet, so the range can't be found, and the operation fails with -EPROBE_DEFER. - Exchanging the order of the calls to gpiochip_add() and gpiochip_add_pin_range() is not an option, as the latter depends on initialization done by the former. - Just moving the call of of_gpiochip_scan_hogs() from gpiochip_add() to gpiochip_add_pin_range() is also not an option, as the latter is optional, and thus not used by all drivers. Hence if of_gpiochip_scan_hogs() fails with -EPROBE_DEFER, call it again every time the pin range is changed, until it succeeded. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> --- Questions: - Is there a better solution to handle this? - Should the pin ranges be configured by passing an array of data to gpiochip_add() instead of having calls to gpiochip_add_pin_range()? That would require changing all drivers. - What happens if you have multiple hogs in multiple ranges? The first hog(s) may be configured multiple times. Is that a problem? - In one of the threads that discussed the GPIO hogging mechanism, Maxime Ripard said: "Our pinctrl driver is also our GPIO driver, so they both share the same node." Maxime: Did you try GPIO hogging? Did it work? If yes, which driver are you using? What's different compared to sh-pfc? If no, did you get it to work? Thanks! --- drivers/gpio/gpiolib-of.c | 21 +++++++++++++++++---- drivers/gpio/gpiolib.c | 1 + include/linux/gpio/driver.h | 1 + include/linux/of_gpio.h | 2 ++ 4 files changed, 21 insertions(+), 4 deletions(-)