Re: [PATCH v2] pinctrl: bcm63268: add gpio function

[Álvaro Fernández Rojas]

El sáb, 4 ene 2025 a las 20:32, Jonas Gorski
(<jonas.gorski@xxxxxxxxx>) escribió:
>
> On Sat, Jan 4, 2025 at 6:02 PM Álvaro Fernández Rojas <noltari@xxxxxxxxx> wrote:
> >
> > El sáb, 4 ene 2025 a las 16:44, Álvaro Fernández Rojas
> > (<noltari@xxxxxxxxx>) escribió:
> > >
> > > El vie, 3 ene 2025 a las 4:04, Kyle Hendry (<kylehendrydev@xxxxxxxxx>) escribió:
> > > >
> > > > On 2024-12-30 08:42, Jonas Gorski wrote:
> > > > > Hi,
> > > > >
> > > > > On Tue, Dec 24, 2024 at 11:41 AM Álvaro Fernández Rojas
> > > > > <noltari@xxxxxxxxx> wrote:
> > > > >> From: Kyle Hendry <kylehendrydev@xxxxxxxxx>
> > > > >>
> > > > >> There is no guarantee that the bootloader will leave the pin configuration
> > > > >> in a known default state, so pinctrl needs to be explicitly set in some
> > > > >> cases. This patch adds a gpio function for drivers that need it, i.e.
> > > > >> gpio-leds.
> > > > >>
> > > > >> Signed-off-by: Kyle Hendry <kylehendrydev@xxxxxxxxx>
> > > > >> Signed-off-by: Álvaro Fernández Rojas <noltari@xxxxxxxxx>
> > > > >
> > > > > bcm63268-pinctrl implements pinmux_ops::gpio_request_enable(), which
> > > > > should automatically set any requested GPIO pin to the GPIO function,
> > > > > so explicitly requesting the gpio function for a pin should not be
> > > > > needed. Is this not enough?
> > > > >
> > > > > Best Regards,
> > > > > Jonas
> > > > >
> > > > >
> > > > I assumed that as well, but nothing I tried worked with gpio-leds.
> > > > gpiochip_generic_request() does call gpio_request_enable(), but gpio-leds
> > > > uses devm_fwnode_gpiod_get() which looks like a different code path. The
> > > > only place it seems to be configuring the gpio is in create_gpio_led()
> > > > where it needs a pinctl node in the device tree. That's just my reading
> > > > of the code, though. I haven't set up a ftrace to verify it.
> > > >
> > > > Best Regards,
> > > > Kyle
> > >
> > > As Kyle pointed out it's not enough and gpio_request_enable() doesn't
> > > get called from gpio-leds.
> > > I will try to investigate this and report back.
> > >
> > > Best regards,
> > > Álvaro.
> >
> > I've performed some tests and so far I haven't been able to get
> > bcm63268_gpio_request_enable() called.
> >
> > Even exporting a gpio from userspace doesn't trigger that function,
> > which seems strange because in that case we won't have a "gpio"
> > function on the pinctrl for that gpio, even with this patch...
>
> On a first glance it looks like that regmap-gpio does not populate
> gpio_chip::request and gpio_chip:free, so the gpio subsystem is not
> aware that it needs to request anything. Not sure if just using
> gpiolib_generic_request() / gpiolib_generic_free() is fine. Currently
> on vacation, so no hardware to test anything at hand ;-)
>
> Best Regards,
> Jonas

You're totally right, after adding request() and free() functions to
gpio-regmap it's now working without this patch because
bcm63268_gpio_request_enable() is now properly called:
1. gpio-keys-polled
[    4.052132] gpio_button_hotplug: loading out-of-tree module taints kernel.
[    4.060657] bcm63268-pinctrl 100000d0.pinctrl: request pin 34
(gpio34) for 100000d0.pinctrl:546
[    4.069704] bcm63268_gpio_request_enable: range=99a2e0ae offset=34
[    4.076158] bcm63268-pinctrl 100000d0.pinctrl: request pin 35
(gpio35) for 100000d0.pinctrl:547
[    4.085135] bcm63268_gpio_request_enable: range=99a2e0ae offset=35

2. gpio-leds
[    4.480190] bcm63268-pinctrl 100000d0.pinctrl: request pin 0
(gpio0) for 100000d0.pinctrl:512
[    4.489078] bcm63268_gpio_request_enable: range=99a2e0ae offset=0
[    4.495747] bcm63268-pinctrl 100000d0.pinctrl: request pin 1
(gpio1) for 100000d0.pinctrl:513
[    4.504600] bcm63268_gpio_request_enable: range=99a2e0ae offset=1

3. userspace gpio export
root@OpenWrt:~# cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 512-563, parent: platform/100000d0.pinctrl, 100000d0.pinctrl:
 gpio-512 (                    |red:mobile          ) out lo
 gpio-513 (                    |green:mobile        ) out lo
 gpio-546 (                    |wps                 ) in  hi ACTIVE LOW
 gpio-547 (                    |reset               ) in  hi ACTIVE LOW
root@OpenWrt:~# echo 545 > /sys/class/gpio/export
[   33.437477] bcm63268-pinctrl 100000d0.pinctrl: request pin 33
(gpio33) for 100000d0.pinctrl:545
[   33.446503] bcm63268_gpio_request_enable: range=99a2e0ae offset=33
root@OpenWrt:~# cat /sys/kernel/debug/gpio
gpiochip0: GPIOs 512-563, parent: platform/100000d0.pinctrl, 100000d0.pinctrl:
 gpio-512 (                    |red:mobile          ) out lo
 gpio-513 (                    |green:mobile        ) out lo
 gpio-545 (                    |sysfs               ) in  hi
 gpio-546 (                    |wps                 ) in  hi ACTIVE LOW
 gpio-547 (                    |reset               ) in  hi ACTIVE LOW

OpenWrt test source code:
https://github.com/Noltari/openwrt/commits/bmips-gpio-tests
https://github.com/Noltari/openwrt/commit/d3bc7610c8fe8f713a3e47ed8368b6aa220ae763

Linux test source code:
https://github.com/Noltari/linux/commits/gpio-regmap-pinctrl-request-free
https://github.com/Noltari/linux/commit/2d0ebb8cad8084e932f40f3f69d4e931b2316aa4

@Linus I assume that adding those functions may cause issues to other
drivers and maybe we need to add some logic to add them dynamically
based on a new gpio_regmap_config parameter?

Best regards,
Álvaro.