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docs: firmware-guide: ACPI: Add a PWM example

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When PWM support for ACPI has been added into the kernel, it missed
the documentation update. Hence update documentation here.

Fixes: 4a6ef8e37c ("pwm: Add support referencing PWMs from ACPI")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Andy Shevchenko 2021-06-07 15:24:53 +03:00 committed by Thierry Reding
parent 9939648a53
commit ef3d13b867
1 changed files with 32 additions and 0 deletions
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32
Documentation/firmware-guide/acpi/enumeration.rst
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@ -258,6 +258,38 @@ input driver::
.id_table = mpu3050_ids,
};
Reference to PWM device
=======================
Sometimes a device can be a consumer of PWM channel. Obviously OS would like
to know which one. To provide this mapping the special property has been
introduced, i.e.::
Device (DEV)
{
Name (_DSD, Package ()
{
ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
Package () {
Package () { "compatible", Package () { "pwm-leds" } },
Package () { "label", "alarm-led" },
Package () { "pwms",
Package () {
"\\_SB.PCI0.PWM", // <PWM device reference>
0, // <PWM index>
600000000, // <PWM period>
0, // <PWM flags>
}
}
}
})
...
In the above example the PWM-based LED driver references to the PWM channel 0
of \_SB.PCI0.PWM device with initial period setting equal to 600 ms (note that
value is given in nanoseconds).
GPIO support
============