[PATCH v17 RESEND 3/3] docs: leds: Add MT6370 RGB LED pattern document

[ChiaEn Wu]

From: ChiYuan Huang <cy_huang at richtek.com>

Document the MT6370 RGB LED pattern trigger.

This simply describe how the pattern works, each timing period, and the
pattern diagram for MT6370 RGB LED.

Signed-off-by: ChiYuan Huang <cy_huang at richtek.com>
Signed-off-by: ChiaEn Wu <chiaen_wu at richtek.com>
---
 Documentation/leds/leds-mt6370-rgb.rst | 64 ++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 Documentation/leds/leds-mt6370-rgb.rst

diff --git a/Documentation/leds/leds-mt6370-rgb.rst b/Documentation/leds/leds-mt6370-rgb.rst
new file mode 100644
index 00000000..d1b2e4f
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+.. SPDX-License-Identifier: GPL-2.0
+
+=========================================
+Kernel driver for Mediatek MT6370 RGB LED
+=========================================
+
+Description
+-----------
+
+The MT6370 integrates a four-channel RGB LED driver, designed to provide a
+variety of lighting effect for mobile device applications. The RGB LED driver
+includes a smart LED string controller and it can drive 3 channels of LEDs with
+a sink current up to 24mA and a CHG_VIN power good indicator LED with sink
+current up to 6mA. It provides three operation modes for RGB LEDs:
+PWM Dimming mode, breath pattern mode, and constant current mode. The device
+can increase or decrease the brightness of the RGB LED via I2C interface.
+
+The breath pattern for a channel can be programmed using the "pattern" trigger,
+using the hw_pattern attribute.
+
+/sys/class/leds/<led>/hw_pattern
+--------------------------------
+
+Specify a hardware breath pattern for a MT6370 RGB LED.
+
+The breath pattern is a series of timing pairs, with the hold-time expressed in
+milliseconds. And the brightness is controlled by
+'/sys/class/leds/<led>/brightness'. The pattern doesn't include the brightness
+setting. Hardware pattern only controls the timing for each pattern stage
+depending on the current brightness setting.
+
+Pattern diagram::
+
+     "0 Tr1 0 Tr2 0 Tf1 0 Tf2 0 Ton 0 Toff" --> '0' for dummy brightness code
+
+      ^
+      |           ============
+      |          /            \                                /
+Icurr |         /              \                              /
+      |        /                \                            /
+      |       /                  \                          /   .....repeat
+      |      /                    \                        /
+      |   ---                      ---                  ---
+      |---                            ---            ---
+      +----------------------------------============------------> Time
+       < Tr1><Tr2><   Ton    ><Tf1><Tf2 ><  Toff    >< Tr1><Tr2>
+
+Timing description::
+
+Tr1:    First rising time for duty 0 to 30%.
+Tr2:    Second rising time for duty 31% to 100%.
+Ton:    On time for duty 100%.
+Tf1:    First falling time for duty 100% to 31%.
+Tf2:    Second falling time for duty 30% to 0%.
+Toff:   Off time for duty 0%.
+
+Tr1/Tr2/Tf1/Tf2/Ton: 125ms to 3125ms, 200ms per step.
+Toff: 250ms to 6250ms, 400ms per step.
+
+Pattern example::
+
+       "0 125 0 125 0 125 0 125 0 625 0 1050"
+
+This Will configure Tr1/Tr2/Tf1/Tf2 to 125m, Ton to 625ms, and Toff to 1050ms.
-- 
2.7.4