* [PATCH v1 1/1] Documentation: firmware-guide: gpio-properties: Add note to SPI CS case
@ 2021-04-24 14:39 Andy Shevchenko
2021-04-28 17:12 ` Rafael J. Wysocki
0 siblings, 1 reply; 2+ messages in thread
From: Andy Shevchenko @ 2021-04-24 14:39 UTC (permalink / raw)
To: Andy Shevchenko, Rafael J. Wysocki, linux-gpio, linux-acpi, linux-kernel
Cc: Mika Westerberg, Rafael J. Wysocki, Len Brown
Historically ACPI has no means of the GPIO polarity and thus
the SPISerialBus() resource defines it on the per-chip basis.
In order to avoid an ambiguity, the GPIO polarity is considered
being always Active High.
Add note about this to the respective documentation file.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
Documentation/firmware-guide/acpi/gpio-properties.rst | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/Documentation/firmware-guide/acpi/gpio-properties.rst b/Documentation/firmware-guide/acpi/gpio-properties.rst
index 4e264c16ddff..df4b711053ee 100644
--- a/Documentation/firmware-guide/acpi/gpio-properties.rst
+++ b/Documentation/firmware-guide/acpi/gpio-properties.rst
@@ -99,6 +99,12 @@ native::
}
}
+Note, that historically ACPI has no means of the GPIO polarity and thus
+the SPISerialBus() resource defines it on the per-chip basis. In order
+to avoid a chain of negations, the GPIO polarity is considered being
+Active High. Even for the cases when _DSD() is involved (see the example
+above) the GPIO CS polarity must be defined Active High to avoid ambiguity.
+
Other supported properties
==========================
--
2.30.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v1 1/1] Documentation: firmware-guide: gpio-properties: Add note to SPI CS case
2021-04-24 14:39 [PATCH v1 1/1] Documentation: firmware-guide: gpio-properties: Add note to SPI CS case Andy Shevchenko
@ 2021-04-28 17:12 ` Rafael J. Wysocki
0 siblings, 0 replies; 2+ messages in thread
From: Rafael J. Wysocki @ 2021-04-28 17:12 UTC (permalink / raw)
To: Andy Shevchenko
Cc: Rafael J. Wysocki, open list:GPIO SUBSYSTEM,
ACPI Devel Maling List, Linux Kernel Mailing List,
Mika Westerberg, Rafael J. Wysocki, Len Brown
On Sat, Apr 24, 2021 at 4:39 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> Historically ACPI has no means of the GPIO polarity and thus
> the SPISerialBus() resource defines it on the per-chip basis.
> In order to avoid an ambiguity, the GPIO polarity is considered
> being always Active High.
>
> Add note about this to the respective documentation file.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> Documentation/firmware-guide/acpi/gpio-properties.rst | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/firmware-guide/acpi/gpio-properties.rst b/Documentation/firmware-guide/acpi/gpio-properties.rst
> index 4e264c16ddff..df4b711053ee 100644
> --- a/Documentation/firmware-guide/acpi/gpio-properties.rst
> +++ b/Documentation/firmware-guide/acpi/gpio-properties.rst
> @@ -99,6 +99,12 @@ native::
> }
> }
>
> +Note, that historically ACPI has no means of the GPIO polarity and thus
> +the SPISerialBus() resource defines it on the per-chip basis. In order
> +to avoid a chain of negations, the GPIO polarity is considered being
> +Active High. Even for the cases when _DSD() is involved (see the example
> +above) the GPIO CS polarity must be defined Active High to avoid ambiguity.
> +
> Other supported properties
> ==========================
>
> --
Applied as 5.13-rc material, thanks!
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2021-04-24 14:39 [PATCH v1 1/1] Documentation: firmware-guide: gpio-properties: Add note to SPI CS case Andy Shevchenko
2021-04-28 17:12 ` Rafael J. Wysocki
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