Commit ef3d13b8 authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Thierry Reding
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docs: firmware-guide: ACPI: Add a PWM example 



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

Fixes: 4a6ef8e3 ("pwm: Add support referencing PWMs from ACPI")
Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent 9939648a

Documentation/firmware-guide/acpi/enumeration.rst

+32 −0
Original line number Diff line number Diff line
@@ -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

============