[PATCH v4 58/59] acpi: Add more documentation for struct acpi_gpio

[Simon Glass]

Hi Andy,

On Thu, 29 Oct 2020 at 06:22, Andy Shevchenko
<andriy.shevchenko at linux.intel.com> wrote:
>
> On Tue, Sep 22, 2020 at 12:45:43PM -0600, Simon Glass wrote:
> > Add some documentation provided by Andy Shevchenko to describe how to
> > use struct acpi_gpio.
>
> Thanks!
>
> I see Bin already applied this, perhaps follow up fix is needed. See below.
>
> ...
>
> > + * Note that GpioIo doesn't have any means of Active Low / High setting, so a
>
> GpioIo -> GpioIo()
>
> > + * _DSD must be provided to mitigate this.
>
> Plus the following:
>
> "This parameter does not make sense for GpioInt() since it has its own means
> to define it."
>
> > + * GpioIo doesn't properly communicate the initial state of the output pin,
>
> GpioIo -> GpioIo()
>
> > + * thus Linux assumes the simple rule:
> > + *
> > + * Pull Bias       Polarity      Requested...
> > + *
> > + * Implicit        x             AS IS (assumed firmware configured for us)
> > + * Explicit        x (no _DSD)   as Pull Bias (Up == High, Down == Low),
> > + *                               assuming non-active (Polarity = !Pull Bias)
> > + *
> > + * Down            Low           as low, assuming active
>
> > + * Down            High          as high, assuming non-active
>
> Should be read:
>
> " * Down            High          as low, assuming non-active"
>
> > + * Up              Low           as high, assuming non-active
> > + * Up              High          as high, assuming active
> > + *
> > + * GpioIo() can be used as interrupt and in this case the IoRestriction mustn't
> > + * be OutputOnly.
> > + * It also requires active_low flag from _DSD in cases where it's
> > + * needed (better to always provide than rely on above assumption made on OS
> > + * level).
>

Thanks, I sent a patch for these.

Regards,
Simon