[PATCH v2 1/7] docs: firmware-guide: ACPI: Add a PWM example

Andy Shevchenko
2021-05-31T19:49:44Z

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>
---
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