Merge tag 'pwm/for-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm

Pull pwm updates from Thierry Reding:
 "This contains mostly various fixes, cleanups and some conversions to
  the atomic API. One noteworthy change is that PWM consumers can now
  pass a hint to the PWM core about the PWM usage, enabling PWM
  providers to implement various optimizations.

  There's also a fair bit of simplification here with the addition of
  some device-managed helpers as well as unification between the DT and
  ACPI firmware interfaces"

* tag 'pwm/for-5.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm: (50 commits)
  pwm: Remove redundant assignment to pointer pwm
  pwm: ep93xx: Fix read of uninitialized variable ret
  pwm: ep93xx: Prepare clock before using it
  pwm: ep93xx: Unfold legacy callbacks into ep93xx_pwm_apply()
  pwm: ep93xx: Implement .apply callback
  pwm: vt8500: Only unprepare the clock after the pwmchip was removed
  pwm: vt8500: Drop if with an always false condition
  pwm: tegra: Assert reset only after the PWM was unregistered
  pwm: tegra: Don't needlessly enable and disable the clock in .remove()
  pwm: tegra: Don't modify HW state in .remove callback
  pwm: tegra: Drop an if block with an always false condition
  pwm: core: Simplify some devm_*pwm*() functions
  pwm: core: Remove unused devm_pwm_put()
  pwm: core: Unify fwnode checks in the module
  pwm: core: Reuse fwnode_to_pwmchip() in ACPI case
  pwm: core: Convert to use fwnode for matching
  docs: firmware-guide: ACPI: Add a PWM example
  dt-bindings: pwm: pwm-tiecap: Add compatible string for AM64 SoC
  dt-bindings: pwm: pwm-tiecap: Convert to json schema
  pwm: sprd: Don't check the return code of pwmchip_remove()
  ...

1 files changed, 32 insertions, 0 deletions

diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst
index 18074eb71860..74b830b2fd59 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
 ============