1 .. SPDX-License-Identifier: GPL-2.0
2
3 ==============================
4 Kernel driver for Qualcomm LPG
5 ==============================
6
7 Description
8 -----------
9
10 The Qualcomm LPG can be found in a variety of
11 number of PWM channels, a programmable pattern
12 current sink.
13
14 To facilitate the various use cases, the LPG c
15 individual LEDs, grouped together as RGB LEDs
16 channels. The output of each PWM channel is ro
17 blocks, such as the RGB current sink, GPIO pin
18
19 The each PWM channel can operate with a period
20 has a 9 bit resolution of the duty cycle.
21
22 In order to provide support for status notific
23 deeper idle states the LPG provides pattern su
24 lookup table of brightness values and per chan
25 range within the table to use, the rate and if
26
27 The pattern for a channel can be programmed us
28 the hw_pattern attribute.
29
30 /sys/class/leds/<led>/hw_pattern
31 --------------------------------
32
33 Specify a hardware pattern for a Qualcomm LPG
34
35 The pattern is a series of brightness and hold
36 expressed in milliseconds. The hold time is a
37 therefore be identical for each element in the
38 described below). As the LPG hardware is not a
39 transitions expected by the leds-trigger-patte
40 pattern must be followed a zero-length entry o
41
42 Simple pattern::
43
44 "255 500 255 0 0 500 0 0"
45
46 ^
47 |
48 255 +----+ +----+
49 | | | | ...
50 0 | +----+ +----
51 +---------------------->
52 0 5 10 15 time (100ms)
53
54 The LPG supports specifying a longer hold-time
55 in the pattern, the so called "low pause" and
56
57 Low-pause pattern::
58
59 "255 1000 255 0 0 500 0 0 255 500 255 0 0
60
61 ^
62 |
63 255 +--------+ +----+ +----+ +---
64 | | | | | | |
65 0 | +----+ +----+ +----+
66 +----------------------------->
67 0 5 10 15 20 25 time (100m
68
69 Similarly, the last entry can be stretched by
70 last entry.
71
72 In order to save space in the shared lookup ta
73 mode, in which case each run through the patte
74 the pattern forward, then backwards. This mode
75 driver when the given pattern is a palindrome.
76 denotes the wait time before the pattern is ru
77 specified hold-time of the middle item in the
78 different hold-time.
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