linux-kernel - Re: [PATCH v6 2/3] gpio: add a reusable generic gpio

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Date:   Thu, 28 May 2020 19:03:02 +0200
From:   Michael Walle <michael@...le.cc>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Mark Brown <broonie@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v6 2/3] gpio: add a reusable generic gpio_chip using
 regmap

Am 2020-05-28 17:55, schrieb Pierre-Louis Bossart:
>> +    /* if we have a direction register we need both input and
>> output */
>> +    if ((config->reg_dir_out_base || config->reg_dir_in_base) &&
>> +        (!config->reg_dat_base || !config->reg_set_base))
>> +        return ERR_PTR(-EINVAL);
>  This failed for me since I didn't have the 'dat' base assigned. I
> still can't figure out what 'dat' stands for...I just assigned it to
> the same offset as the 'set' base but really don't understand what
> this is supposed to do.

DAT is the data register, aka input register, if the GPIO is in input
mode.

If I read the datasheet correctly you should use the following:

PCM512x_GPIO_EN should be reg_dir_out_base
PCM512x_GPIO_CONTROL_1 should be reg_set_base
PCM512x_GPIN should be reg_dat_base

no custom xlate necessary. GPIN looks a bit fishy in that datasheet:
  http://www.ti.com/lit/ds/symlink/pcm5121.pdf?ts=1590684141147

PCM512x_GPIO_OUTPUT_1..6 is pinmux control and shouldn't be part of
the gpio-regmap. Your driver needs to take care of that.

>> +
>> +    /* we don't support having both registers simultaneously for
>> now */
>> +    if (config->reg_dir_out_base && config->reg_dir_in_base)
>> +        return ERR_PTR(-EINVAL);
> 
> and this second test seems to contradict the notion of 'both input and
> output' above?

dir_out_base is used if the register is high active to select an output.
dir_in_base is used for a low active register. Thus both bases are used
to switch a GPIO between input and output.

> re-adding comment from previous series:
>  >> I still have a series of odd warnings I didn't have before: >> >>
> [  101.400263] WARNING: CPU: 3 PID: 1129 at >>
> drivers/gpio/gpiolib.c:4084 gpiod_set_value+0x3f/0x50 >> >> This seems
> to come from >>     /* Should be using gpiod_set_value_cansleep() */
>>>     WARN_ON(desc->gdev->chip->can_sleep); > > Right now,
> gpio-regmap hardcodes can_sleep to true. But the only regmap > which
> don't sleep is regmap-mmio. The PCM512x seems to be either I2C or >
> SPI, which can both sleep. So this warning is actually correct and >
> wherever this gpio is set should do it by calling the _cansleep() >
> version.
> 
> I still have the warnings with this version, not sure if you wanted to
> fix it in the v6 or is this needs to be fixed in another piece of
> code/patch. How would we go about removing this warning?

There is no fix in gpio-regmap. wherever this GPIO is connected to must
not call gpiod_set_value() but have to use gpiod_set_value_cansleep().

-michael