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SubjectRe: Backlight in motorola Droid 4
From
Date
Pavel

On 7/24/19 7:45 AM, Pavel Machek wrote:
> Hi!
>
>>> So now the backlight LED can be controlled. Good. (And thanks!)
>>>
>>> But I seem to remember that backlight had range from "is it really on?"
>>> to "very bright"; now it seems to have range from "bright" to "very
>>> bright".
>>>
>>> Any ideas what goes on there?
>> In the LM3552 driver we are changing the Full scale brightness registers for
>> the
>>
>> specific control bank.
>>
>> #define LM3532_REG_CTRL_A_BRT    0x17
>> #define LM3532_REG_CTRL_B_BRT    0x19
>> #define LM3532_REG_CTRL_C_BRT    0x1b
>>
>> In the ti-lmu code the ALS zones were being modified not the control bank
>> brightness.
>>
>> #define LM3532_REG_BRT_A            0x70    /* zone 0 */
>> #define LM3532_REG_BRT_B            0x76    /* zone 1 */
>> #define LM3532_REG_BRT_C            0x7C    /* zone 2 */
>>
>> Not sure how the ALS is attached in the system if it reports to the host and
>> the host manages
>>
>> the back light or if the the ALS is connected directly to the LM3532.
>>
>> Maybe the ALS zone targets need to be updated to allow a fuller range.  The
>> LM3532 may be stuck
>>
>> in a certain zone.
>>
>> Probably should set up the ALS properties in the device tree.
> I came with this so far.

OK I guess you will remove the commentary in the driver once you submit

the patch


> Pavel
>
> diff --git a/arch/arm/boot/dts/omap4-droid4-xt894.dts b/arch/arm/boot/dts/omap4-droid4-xt894.dts
> index 62af1b8..752952e 100644
> --- a/arch/arm/boot/dts/omap4-droid4-xt894.dts
> +++ b/arch/arm/boot/dts/omap4-droid4-xt894.dts
> @@ -422,6 +422,7 @@
> led-sources = <2>;
> ti,led-mode = <0>;
> label = ":backlight";
> + default-state = "on";
> linux,default-trigger = "backlight";
> };
>
> diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
> index e5e1b3a..2baeacd 100644
> --- a/drivers/base/regmap/regmap-debugfs.c
> +++ b/drivers/base/regmap/regmap-debugfs.c
> @@ -288,7 +288,7 @@ static ssize_t regmap_map_read_file(struct file *file, char __user *user_buf,
> count, ppos);
> }
>
> -#undef REGMAP_ALLOW_WRITE_DEBUGFS
> +#define REGMAP_ALLOW_WRITE_DEBUGFS
> #ifdef REGMAP_ALLOW_WRITE_DEBUGFS
> /*
> * This can be dangerous especially when we have clients such as
> diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
> index bdc98dd..db6e382 100644
> --- a/drivers/leds/leds-gpio.c
> +++ b/drivers/leds/leds-gpio.c
> @@ -172,6 +172,7 @@ static struct gpio_leds_priv *gpio_leds_create(struct platform_device *pdev)
> led.default_state = LEDS_GPIO_DEFSTATE_ON;
> else
> led.default_state = LEDS_GPIO_DEFSTATE_OFF;
> + /* FIXME: else ... warn about bad device tree */
> }
>
> if (fwnode_property_present(child, "retain-state-suspended"))
> diff --git a/drivers/leds/leds-lm3532.c b/drivers/leds/leds-lm3532.c
> index 180895b..365a22a5 100644
> --- a/drivers/leds/leds-lm3532.c
> +++ b/drivers/leds/leds-lm3532.c
> @@ -1,6 +1,7 @@
> // SPDX-License-Identifier: GPL-2.0
> // TI LM3532 LED driver
> // Copyright (C) 2019 Texas Instruments Incorporated - http://www.ti.com/
> +// http://www.ti.com/lit/ds/symlink/lm3532.pdf

I don't put symlinks in drivers as they are subject to change.

This link is in the patch history anyway


>
> #include <linux/i2c.h>
> #include <linux/leds.h>
> @@ -23,7 +24,7 @@
> #define LM3532_REG_PWM_B_CFG 0x14
> #define LM3532_REG_PWM_C_CFG 0x15
> #define LM3532_REG_ZONE_CFG_A 0x16
> -#define LM3532_REG_CTRL_A_BRT 0x17
> +#define LM3532_REG_CTRL_A_BRT 0x17 /* Called "Control A Full-Scale Current " in documentation */
> #define LM3532_REG_ZONE_CFG_B 0x18
> #define LM3532_REG_CTRL_B_BRT 0x19
> #define LM3532_REG_ZONE_CFG_C 0x1a
> @@ -38,6 +39,7 @@
> #define LM3532_REG_ZN_2_LO 0x65
> #define LM3532_REG_ZN_3_HI 0x66
> #define LM3532_REG_ZN_3_LO 0x67
> +#define LM3532_REG_ZN_TARGET 0x70
> #define LM3532_REG_MAX 0x7e
>
> /* Contorl Enable */
> @@ -302,7 +304,7 @@ static int lm3532_led_disable(struct lm3532_led *led_data)
> int ret;
>
> ret = regmap_update_bits(led_data->priv->regmap, LM3532_REG_ENABLE,
> - ctrl_en_val, ~ctrl_en_val);
> + ctrl_en_val, 0);
> if (ret) {
> dev_err(led_data->priv->dev, "Failed to set ctrl:%d\n", ret);
> return ret;
> @@ -321,6 +323,7 @@ static int lm3532_brightness_set(struct led_classdev *led_cdev,
>
> mutex_lock(&led->priv->lock);
>
> + /* Actually, I don't think this is acceptable */
> if (led->mode == LM3532_BL_MODE_ALS) {
> if (brt_val > LED_OFF)
> ret = lm3532_led_enable(led);
> @@ -339,11 +342,23 @@ static int lm3532_brightness_set(struct led_classdev *led_cdev,
> if (ret)
> goto unlock;
>
> + /* This driver is sick. It manipulates maximum current register (5-bit),
> + but fails to control 8-bit brightness register... which is exponential
> + so it allows >8 bit of control */
> +

> brightness_reg = LM3532_REG_CTRL_A_BRT + led->control_bank * 2;
The appropriate target register can be programmed in the control bank
config register bits[4:2]

Default is 0x1xx which is 0x74.

The target register should be set in the config as well and then stored
as a register offset.

Or just set the CTRL_A_BRT to 0x74 and take the default config

> - brt_val = brt_val / LM3532_BRT_VAL_ADJUST;
> + brt_val = 255 / LM3532_BRT_VAL_ADJUST;
>

Don't need this if we have 8 bit control.  This was only needed for the
max current control.


> ret = regmap_write(led->priv->regmap, brightness_reg, brt_val);
>
> + brightness_reg = 0x70 + led->control_bank * 5;
> +
> + ret = regmap_write(led->priv->regmap, brightness_reg, brt_val);
> + ret = regmap_write(led->priv->regmap, brightness_reg+1, brt_val);
> + ret = regmap_write(led->priv->regmap, brightness_reg+2, brt_val);
> + ret = regmap_write(led->priv->regmap, brightness_reg+3, brt_val);
> + ret = regmap_write(led->priv->regmap, brightness_reg+4, brt_val);
> +

You don't need to write all the target registers.

Dan

<snip>


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