From: Ricardo Ribalda <ribalda@chromium.org>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>,
linux-acpi@vger.kernel.org,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
linux-gpio@vger.kernel.org
Subject: Re: [PATCH v1 2/3] Documentation: firmware-guide: gpio-properties: active_low only for GpioIo()
Date: Wed, 28 Oct 2020 22:10:42 +0100 [thread overview]
Message-ID: <CANiDSCtRDwfFo9HE84iujjFe6h9aS6b3B8wkz5Rt0aO8=XMsNg@mail.gmail.com> (raw)
In-Reply-To: <20201028205101.47583-2-andriy.shevchenko@linux.intel.com>
Hi Andy
Thanks for your patch and super fast response.
I think there are two different concepts here:
1) when the pin has a low value, it is 0 or a 1? =>active_low
2) when do I get an irq, low->high or high->low => irq polarity
When I read the acpi spec for GpioInt()
https://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf page
934, it has the same problem as for GpioIo(), it does not express the
active_low and this is where the _DSD field comes handy.
Without using the active_low, how can we describe a pin that is
active low and has to trigger an irq on both edges?
Thanks again
On Wed, Oct 28, 2020 at 9:51 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> It appears that people may misinterpret active_low field in _DSD
> for GpioInt() resource. Add a paragraph to clarify this.
>
> Reported-by: Ricardo Ribalda <ribalda@chromium.org>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> Documentation/firmware-guide/acpi/gpio-properties.rst | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/Documentation/firmware-guide/acpi/gpio-properties.rst b/Documentation/firmware-guide/acpi/gpio-properties.rst
> index e6e65ceb2ca1..370fe46c6af9 100644
> --- a/Documentation/firmware-guide/acpi/gpio-properties.rst
> +++ b/Documentation/firmware-guide/acpi/gpio-properties.rst
> @@ -55,6 +55,9 @@ Since ACPI GpioIo() resource does not have a field saying whether it is
> active low or high, the "active_low" argument can be used here. Setting
> it to 1 marks the GPIO as active low.
>
> +Note, active_low in _DSD does not make sense for GpioInt() resource and
> +must be 0. GpioInt() resource has its own means of defining it.
> +
> In our Bluetooth example the "reset-gpios" refers to the second GpioIo()
> resource, second pin in that resource with the GPIO number of 31.
>
> --
> 2.28.0
>
--
Ricardo Ribalda
next prev parent reply other threads:[~2020-10-28 21:37 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-28 20:50 [PATCH v1 1/3] Documentation: firmware-guide: gpio-properties: Fix factual mistakes Andy Shevchenko
2020-10-28 20:51 ` [PATCH v1 2/3] Documentation: firmware-guide: gpio-properties: active_low only for GpioIo() Andy Shevchenko
2020-10-28 21:10 ` Ricardo Ribalda [this message]
2020-10-29 14:46 ` Andy Shevchenko
2020-10-29 14:54 ` Ricardo Ribalda
2020-10-29 17:17 ` Andy Shevchenko
2020-10-29 17:20 ` Andy Shevchenko
2020-10-29 17:25 ` Andy Shevchenko
2020-10-29 17:32 ` Ricardo Ribalda
2020-10-29 18:09 ` Ricardo Ribalda
2020-10-29 18:13 ` Andy Shevchenko
2020-10-29 18:58 ` Ricardo Ribalda
2020-10-29 19:11 ` Andy Shevchenko
2020-10-29 18:10 ` Andy Shevchenko
2020-10-29 8:13 ` Mika Westerberg
2020-10-28 20:51 ` [PATCH v1 3/3] Documentation: firmware-guide: gpio-properties: Clarify initial output state Andy Shevchenko
2020-10-29 8:16 ` Mika Westerberg
2020-10-29 8:13 ` [PATCH v1 1/3] Documentation: firmware-guide: gpio-properties: Fix factual mistakes Mika Westerberg
2020-10-29 11:10 ` Andy Shevchenko
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