Re: [PATCH v3 1/6] docs: firmware-guide: ACPI: Add a PWM example
From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: 2021-06-07 12:38:40
Also in:
linux-acpi, linux-pwm, lkml
On Mon, Jun 7, 2021 at 2:24 PM Andy Shevchenko [off-list ref] wrote:
When PWM support for ACPI has been added into the kernel, it missed
the documentation update. Hence update documentation here.
Fixes: 4a6ef8e37c4d ("pwm: Add support referencing PWMs from ACPI")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>Acked-by: Rafael J. Wysocki <redacted> and I'm assuming this to go in via PWM.
quoted hunk ↗ jump to hunk
--- v3: despite flags being optional, don't alter it in the documentation v2: updated example to use 600 ms instead of 600 us (looks saner) .../firmware-guide/acpi/enumeration.rst | 32 +++++++++++++++++++ 1 file changed, 32 insertions(+)diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst index 9f0d5c854fa4..f588663ba906 100644 --- a/Documentation/firmware-guide/acpi/enumeration.rst +++ b/Documentation/firmware-guide/acpi/enumeration.rst@@ -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 ============ --2.30.2