linux-kernel - Re: [PATCH 5.4 regression fix] Input: soc_button_array - partial revert of support for newer surface devices

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Date:   Sat, 5 Oct 2019 15:20:51 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Maximilian Luz <luzmaximilian@...il.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Andy Shevchenko <andy@...radead.org>
Cc:     linux-input@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5.4 regression fix] Input: soc_button_array - partial
 revert of support for newer surface devices

Hi,

On 05-10-2019 14:17, Maximilian Luz wrote:
> Hi,
> 
> sorry for the inconvenience this change has caused.
> 
> On 10/5/19 12:55 PM, Hans de Goede wrote:
>> Note ideally this seamingly unrelated change would have been made in a
>> separate commit, with a message explaining the what and why of this
>> change.
> 
> Would I have known the impact, then yes. This change was added due to
> some reported instances where it seems that soc_button_array would
> occasionally load on MSHW0040 before the GPIO controller was ready,
> causing power and volume buttons to not work.
> 
>> I guess this change may have been added to deal with -EPROBE_DEFER errors,
> 
> Correct. After a comment mentioned that gpiod_get() returning
> -EPROBE_DEFER would be the proper way to detect this, I decided on this
> change.

Ok, on x86 the GPIO drivers really should all be builtin because
various ACPI methods including device D0 / D3 (power-on/off) methods
may depend on them. So normally this should never happen.

If this (-EPROBE_DEFER on surface devices) somehow still is happening
please let me know and we will figure something out.

> Might I suggest the following addition:
> 
> Signed-off-by: Maximilian Luz <luzmaximilian@...il.com>

S-o-b is only for patches which pass through your hands, e.g. if
you make changes to my patch and submit a v2 of it.

I guess you mean / want one of:

Acked-by: ...

or

Reviewed-by: ...


?

Regards,

Hans



> ---
>   drivers/input/misc/soc_button_array.c | 25 ++++++++++++++++++++-----
>   1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/input/misc/soc_button_array.c b/drivers/input/misc/soc_button_array.c
> index 97e3639e99d0..a0f0c977b790 100644
> --- a/drivers/input/misc/soc_button_array.c
> +++ b/drivers/input/misc/soc_button_array.c
> @@ -92,11 +92,18 @@ soc_button_device_create(struct platform_device *pdev,
>               continue;
> 
>           gpio = soc_button_lookup_gpio(&pdev->dev, info->acpi_index);
> -        if (gpio < 0 && gpio != -ENOENT) {
> -            error = gpio;
> -            goto err_free_mem;
> -        } else if (!gpio_is_valid(gpio)) {
> -            /* Skip GPIO if not present */
> +        if (!gpio_is_valid(gpio)) {
> +            /*
> +             * Skip GPIO if not present. Note we deliberately
> +             * ignore -EPROBE_DEFER errors here. On some devices
> +             * Intel is using so called virtual GPIOs which are not
> +             * GPIOs at all but some way for AML code to check some
> +             * random status bits without need a custom opregion.
> +             * In some cases the resources table we parse points to
> +             * such a virtual GPIO, since these are not real GPIOs
> +             * we do not have a driver for these so they will never
> +             * show up, therefor we ignore -EPROBE_DEFER.
> +             */
>               continue;
>           }
> 
> @@ -429,6 +436,14 @@ static int soc_device_check_MSHW0040(struct device *dev)
> 
>       dev_dbg(dev, "OEM Platform Revision %llu\n", oem_platform_rev);
> 
> +    /*
> +     * Explicitly check if GPIO controller is ready. This check is done here
> +     * to avoid issues with virtual GPIOs on other chips, as elaborated above.
> +     * We are at least expecting one GPIO pin for the power button (index 0).
> +     */
> +    if (soc_button_lookup_gpio(dev, 0) == -EPROBE_DEFER)
> +        return -EPROBE_DEFER;
> +
>       return 0;
>   }
>