Re: [PATCH v2 3/3] leds: rt5033: Add RT5033 Flash led device driver

[Jacek Anaszewski <j.anaszewski@samsung.com>]

Hi Ingi,

On 10/13/2015 04:58 AM, Ingi Kim wrote:
> Hi Jacek,
>
> Thanks for your kind comments
> I also append reply below
>
> On 2015년 10월 13일 00:10, Jacek Anaszewski wrote:
>> Hi Ingi,
>>
>> Thanks for the update. Few comments below.
>>
>> On 10/12/2015 03:12 PM, Ingi Kim wrote:
>>> This patch adds device driver of Richtek RT5033 PMIC.
>>> The driver supports a current regulated output to drive
>>> white LEDs for camera flash.
>>>
>>> Signed-off-by: Ingi Kim <ingi2.kim@samsung.com>
>>> ---
>>>    drivers/leds/Kconfig               |   8 ++
>>>    drivers/leds/Makefile              |   1 +
>>>    drivers/leds/leds-rt5033.c         | 223 +++++++++++++++++++++++++++++++++++++
>>>    include/linux/mfd/rt5033-private.h |  49 ++++++++
>>>    include/linux/mfd/rt5033.h         |  22 +++-
>>>    5 files changed, 301 insertions(+), 2 deletions(-)
>>>    create mode 100644 drivers/leds/leds-rt5033.c
>>>
>>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>>> index 42990f2..29613e3 100644
>>> --- a/drivers/leds/Kconfig
>>> +++ b/drivers/leds/Kconfig
>>> @@ -345,6 +345,14 @@ config LEDS_PCA963X
>>>          LED driver chip accessed via the I2C bus. Supported
>>>          devices include PCA9633 and PCA9634
>>>
>>> +config LEDS_RT5033
>>> +    tristate "LED support for RT5033 PMIC"
>>> +    depends on LEDS_CLASS_FLASH && OF
>>> +    depends on MFD_RT5033
>>> +    help
>>> +      This option enables support for on-chip LED driver on
>>> +      RT5033 PMIC.
>>> +
>>>    config LEDS_WM831X_STATUS
>>>        tristate "LED support for status LEDs on WM831x PMICs"
>>>        depends on LEDS_CLASS
>>> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
>>> index b503f92..bcc4d93 100644
>>> --- a/drivers/leds/Makefile
>>> +++ b/drivers/leds/Makefile
>>> @@ -23,6 +23,7 @@ obj-$(CONFIG_LEDS_COBALT_QUBE)        += leds-cobalt-qube.o
>>>    obj-$(CONFIG_LEDS_COBALT_RAQ)        += leds-cobalt-raq.o
>>>    obj-$(CONFIG_LEDS_SUNFIRE)        += leds-sunfire.o
>>>    obj-$(CONFIG_LEDS_PCA9532)        += leds-pca9532.o
>>> +obj-$(CONFIG_LEDS_RT5033)        += leds-rt5033.o
>>>    obj-$(CONFIG_LEDS_GPIO_REGISTER)    += leds-gpio-register.o
>>>    obj-$(CONFIG_LEDS_GPIO)            += leds-gpio.o
>>>    obj-$(CONFIG_LEDS_LP3944)        += leds-lp3944.o
>>> diff --git a/drivers/leds/leds-rt5033.c b/drivers/leds/leds-rt5033.c
>>> new file mode 100644
>>> index 0000000..b470c94
>>> --- /dev/null
>>> +++ b/drivers/leds/leds-rt5033.c
>>> @@ -0,0 +1,223 @@
>>> +/*
>>> + * led driver for RT5033
>>> + *
>>> + * Copyright (C) 2015 Samsung Electronics, Co., Ltd.
>>> + * Ingi Kim <ingi2.kim@samsung.com>
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + *
>>> + */
>>> +
>>> +#include <linux/mfd/rt5033.h>
>>> +#include <linux/mfd/rt5033-private.h>
>>> +#include <linux/module.h>
>>> +#include <linux/platform_device.h>
>>> +
>>> +#define RT5033_LED_FLASH_TIMEOUT_MIN        64000
>>> +#define RT5033_LED_FLASH_TIMEOUT_STEPS        32000
>>> +#define RT5033_LED_TORCH_CURRENT_LEVEL_MAX    16
>>> +
>>> +/* Macro for getting offset of flash timeout */
>>> +#define GET_TIMEOUT_OFFSET(tm, step)    ((tm) / (step) - 2)
>>> +
>>> +static struct rt5033_led *flcdev_to_led(
>>> +                struct led_classdev_flash *fled_cdev)
>>> +{
>>> +    return container_of(fled_cdev, struct rt5033_led, fled_cdev);
>>> +}
>>> +
>>> +static int rt5033_led_brightness_set(struct led_classdev *led_cdev,
>>> +                     enum led_brightness brightness)
>>> +{
>>> +    struct led_classdev_flash *fled_cdev = lcdev_to_flcdev(led_cdev);
>>> +    struct rt5033_led *led = flcdev_to_led(fled_cdev);
>>
>> I assume that you don't use mutex here deliberately?
>>
>
> Actually I'm not sure why flash driver uses mutex.

Which flash driver do you have on mind?

> In consideration of blocking competition, however, I'd be better to use it
>

[...]

>>> +
>>> +static int rt5033_led_flash_strobe_set(struct led_classdev_flash *fled_cdev,
>>> +                       bool state)
>>> +{
>>> +    struct rt5033_led *led = flcdev_to_led(fled_cdev);
>>> +    u32 flash_tm_reg;
>>
>> I think that you need a mutex here and in rt5033_led_flash_strobe_set. Otherwise following is possible:
>>
>> Process 1:
>>      rt5033_led_flash_strobe_set(led_cdev, 1);
>>
>>      regmap_update_bits(led->regmap,    RT5033_REG_FLED_FUNCTION1,
>>              RT5033_FLED_FUNC1_MASK, RT5033_FLED_RESET);
>>      fled_cdev->led_cdev.brightness = LED_OFF;
>>
>> Process 2:
>>      led_set_brightness(led_cdev, 1);
>>
>>      fled_cdev->led_cdev.brightness = 1;
>>
>>      rt5033_led_brightness_set(led_cdev, LED_FULL);
>>
>>      regmap_update_bits(led->regmap, RT5033_REG_FLED_FUNCTION1,
>>              RT5033_FLED_FUNC1_MASK, RT5033_FLED_PINCTRL);
>>      regmap_update_bits(led->regmap,    RT5033_REG_FLED_CTRL1,
>>              RT5033_FLED_CTRL1_MASK,
>>              (brightness - 1) << 4);
>>      regmap_update_bits(led->regmap, RT5033_REG_FLED_FUNCTION2,
>>              RT5033_FLED_CTRL2_MASK, RT5033_FLED_ENFLED);
>>
>> Process 1:
>>      regmap_update_bits(led->regmap,    RT5033_REG_FLED_STROBE_CTRL2,
>>          RT5033_FLED_STRBCTRL2_MASK, flash_tm_reg);
>>      regmap_update_bits(led->regmap,    RT5033_REG_FLED_FUNCTION1,
>>          RT5033_FLED_FUNC1_MASK, RT5033_FLED_STRB_SEL
>>          | RT5033_FLED_PINCTRL);
>>      regmap_update_bits(led->regmap,    RT5033_REG_FLED_FUNCTION2,
>>          RT5033_FLED_FUNC2_MASK, RT5033_FLED_ENFLED
>>
>> In a result LED class device will report brightness value 1,
>> whereas it would be inconsistent with hardware state, since
>> flash strobe turns torch mode off.
>>
>>
>
> Thanks for your explanation in detail,
> I was worried about cases of using shared resource for flash led.
> because I thought flash led would be called just from camera or directly itself.
> I should consider using mutex

You don't provide support for v4l2-flash-led-class and you don't
implement external_strobe_set op. Only if the op is implemented a v4l2
device can switch the strobe source from software to external,
which allows strobing the flash directly by camera sensor or ISP,
but without software interaction.

-- 
Best Regards,
Jacek Anaszewski