[PATCH v2] arm: gpio: Add set_flags callback to the Tegra gpio driver

[Svyatoslav Ryhel]

пн, 29 вер. 2025 р. о 13:22 Łukasz Majewski <lukma at nabladev.com> пише:
>
> Hi Svyatoslav,
>
> > пн, 29 вер. 2025 р. о 10:23 Łukasz Majewski <lukma at nabladev.com> пише:
> > >
> > > Hi Svyatoslav,
> > >
> > > > пн, 22 вер. 2025 р. о 17:16 Lukasz Majewski <lukma at nabladev.com>
> > > > пише:
> > > > >
> > > > > This patch adds support for the .set_flags callback.
> > > > > For now following flags are supported:
> > > > > - GPIOD_IS_AF (i.e. "alternate function").
> > > > > - GPIOD_IS_IN
> > > > > - GPIOD_IS_OUT
> > > > >
> > > > > Currently, the .set_flags in gpio-uclass.c (function
> > > > > dm_gpio_set_value()) is used before .set_value callback, so
> > > > > functionally replaces it. As a result the corresponding
> > > > > tegra_gpio_set_value() can be removed.
> > > > >
> > > > > Signed-off-by: Lukasz Majewski <lukma at nabladev.com>
> > > > > ---
> > > > >
> > > > > Changes for v2:
> > > > > - Fix the format specifier for flags in debug() function
> > > > > - Update commit message
> > > > > - Remove tegra_gpio_set_value() method (as it is functionally
> > > > > replaced by set_value()
> > > > > - Prevent from returning errors when flags = 0 (problem with
> > > > > e.g. I2C GPIO support)
> > > > > ---
> > > > >  drivers/gpio/tegra_gpio.c | 39
> > > > > +++++++++++++++++++++++---------------- 1 file changed, 23
> > > > > insertions(+), 16 deletions(-)
> > > >
> > > > Lukasz, thank you for this change I would really like to see it in
> > > > mainline. ATM I have no capabilities to debug
> > >
> > > You mean test if it works?
> > >
> > > > this and I will return
> > > > to it but that may not be soon unfortunately.
> > >
> > > This is a bit problematic for me, as:
> > >
> > > 1. Some future work depends on it (more details below).
> > > 2. The "set_flags()" callback seems like being now the one to be
> > > advised to being implemented and used.
> > >
> > >
> > >
> > > Can you predict when you will be able to come back to this task? Is
> > > this the matter of weeks or months?
> > >
> >
> > Weeks maybe, I will try to look into this when I have some spare time
> >
>
> Ok.
>
> > > > In case you really need
> > > > switch GPIO back to SFIO and Linux cannot handle this, you an use
> > > > dm_gpio_free to release gpios in board_preboot_os in the board as
> > > > a temporary measure.
> > >
> > > Yes, this is a temporary solution - i.e. dm_gpio_free() is supposed
> > > to "free" the pin. IMHO, the set_flags() shall be used, as I in
> > > fact do want to set the CFG_SFIO flag, not release the gpio.
> > >
> >
> > dm_gpio_free in tegra case calls CFG_SFIO
>
> Yes, but as you said - this is not the "proper" solution.
>
> >
> > > >
> > > > Overall issue you are describing is not u-boot's it is kernels,
> > > > kernel must reconfigure gpios for proper work regardless of their
> > > > previous state. If it is not the case, then kernel device
> > > > configuration is incomplete or wrong.
> > >
> > > This is how the pinmux in Linux for Tegra is written. You can setup
> > > the PAD parameters, but you cannot set the pin's function.
> > >
> >
> > WDYM? Tegra30+ has per-pin configuration, this includes FUNCTION,
> > direction, tristate and pull for all pins
>
> With DTS pinmux description, you cannot change the PAD function
> (special vs gpio) in Linux. It is assumed that bootloader would set the
> function (which, yes, is IMHO a bug).
>
> >
> > > In other words - you have to do it in bootloader (u-boot in this
> > > case).
> > >
> > > In my case - customer uses the pin in u-boot as GPIO to check
> > > carrier board version, then the same pin in Linux is going to be
> > > used as special function one.
> > >
> > > Unfortunately, above "reconfiguration" cannot be done in Linux.
> > >
> > > As other "rework" of gpio code depends on it (use dm) - I would
> > > like to postpone my work until this functionality is available in
> > > mainline (and hence avoid "temporal solutions").
> > >
> > > --
> > > Best regards,

Try this https://source.denx.de/u-boot/custodians/u-boot-tegra/-/commit/d95d942b6e796429342845d153d95330f5257cdd
I have combined your v1 and v2 and added a few tweaks. It works on
star and olympus (tegra20), p895 and grouper (tegra30), tegratab and
tf701t (tegra114) and mocha (tegra124).