LP5521 LED Driver

LP5521 channel과 engine program

National Semiconductor LP5521은 최대 3개 channel을 구동합니다. LED class interface에서 직접 제어할 수 있고 기본 channel 이름은 `lp5521:channel0`부터 `lp5521:channel2`입니다.

세 channel 모두 internal program memory의 engine micro-program으로 제어할 수 있습니다. Instruction 세부 형식은 public datasheet를 참조합니다.

Legacy interface는 engine 1~3마다 `enginex_mode`와 `enginex_load`를 제공합니다. Mode는 `disabled`, `load`, `run`이고 program을 쓰는 `enginex_load`는 engine이 load mode일 때만 보입니다.

두 번째 방법은 LP55xx common firmware interface입니다. 자세한 내용은 `leds-lp55xx.txt`의 firmware section을 참조합니다.

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Kernel driver for lp5521
========================

* National Semiconductor LP5521 led driver chip
* Datasheet: http://www.national.com/pf/LP/LP5521.html

Authors: Mathias Nyman, Yuri Zaporozhets, Samu Onkalo

Contact: Samu Onkalo (samu.p.onkalo-at-nokia.com)

Description
-----------

LP5521 can drive up to 3 channels. Leds can be controlled directly via
the led class control interface. Channels have generic names:
lp5521:channelx, where x is 0 .. 2

All three channels can be also controlled using the engine micro programs.
More details of the instructions can be found from the public data sheet.

LP5521 has the internal program memory for running various LED patterns.
There are two ways to run LED patterns.

1) Legacy interface - enginex_mode and enginex_load
   Control interface for the engines:

   x is 1 .. 3

   enginex_mode:
        disabled, load, run
   enginex_load:
        store program (visible only in engine load mode)

  Example (start to blink the channel 2 led)::

        cd   /sys/class/leds/lp5521:channel2/device
        echo "load" > engine3_mode
        echo "037f4d0003ff6000" > engine3_load
        echo "run" > engine3_mode

  To stop the engine::

        echo "disabled" > engine3_mode

2) Firmware interface - LP55xx common interface

For the details, please refer to 'firmware' section in leds-lp55xx.txt

Selftest와 channel current

Sysfs에는 `selftest` entry가 있습니다. Test는 chip과 통신하고 clock mode가 요청한 값으로 자동 설정되는지 확인합니다.

각 channel은 독립적인 LED current 설정을 갖습니다. `led_current`는 read/write, `max_current`는 read-only입니다. Path 예는 `/sys/class/leds/lp5521:channel0/led_current`와 `max_current`입니다.

Current 값 형식은 0.1mA 단위입니다. 즉 값 `10`은 1.0mA를 뜻합니다.

sysfs contains a selftest entry.

The test communicates with the chip and checks that
the clock mode is automatically set to the requested one.

Each channel has its own led current settings.

- /sys/class/leds/lp5521:channel0/led_current - RW
- /sys/class/leds/lp5521:channel0/max_current - RO

Format: 10x mA i.e 10 means 1.0 mA

example platform data::

  static struct lp55xx_led_config lp5521_led_config[] = {
          {
                .name = "red",
                  .chan_nr        = 0,
                  .led_current    = 50,
                .max_current    = 130,

Platform data 구성

예제 platform data는 red, green, blue 세 `lp55xx_led_config` entry를 channel 0, 1, 2에 연결합니다. Red의 initial current는 50, green과 blue는 0이며 각 `max_current`는 130입니다.

Board code는 hardware resource 준비용 `lp5521_setup`, 해제용 `lp5521_release`, chip enable signal 제어용 `lp5521_enable(bool state)` callback을 제공합니다.

`lp55xx_platform_data`에는 channel config array, `num_channels`, `LP55XX_CLOCK_EXT` clock mode, 세 resource callback을 연결합니다.

`chan_nr`는 0~2입니다. Channel 이름은 설정 가능하고 생략하면 `xxxx:channelN`이 기본값입니다. `xxxx`는 `pdata->label` 또는 I2C client 이름, `N`은 channel 번호입니다.

Platform data에서 current를 0으로 설정한 channel은 비활성화되며 sysfs에도 나타나지 않습니다.

          }, {
                .name = "green",
                  .chan_nr        = 1,
                  .led_current    = 0,
                .max_current    = 130,
          }, {
                .name = "blue",
                  .chan_nr        = 2,
                  .led_current    = 0,
                .max_current    = 130,
          }
  };

  static int lp5521_setup(void)
  {
        /* setup HW resources */
  }

  static void lp5521_release(void)
  {
        /* Release HW resources */
  }

  static void lp5521_enable(bool state)
  {
        /* Control of chip enable signal */
  }

  static struct lp55xx_platform_data lp5521_platform_data = {
          .led_config     = lp5521_led_config,
          .num_channels   = ARRAY_SIZE(lp5521_led_config),
          .clock_mode     = LP55XX_CLOCK_EXT,
          .setup_resources   = lp5521_setup,
          .release_resources = lp5521_release,
          .enable            = lp5521_enable,
  };

Note:
  chan_nr can have values between 0 and 2.
  The name of each channel can be configurable.
  If the name field is not defined, the default name will be set to 'xxxx:channelN'
  (XXXX : pdata->label or i2c client name, N : channel number)


If the current is set to 0 in the platform data, that channel is
disabled and it is not visible in the sysfs.