Re: [PATCH v2 1/2] backlight: pwm_bl: Move the checks for initial power state to a separate function
From: Philipp Zabel <p.zabel@pengutronix.de>
Date: 2016-10-28 13:27:24
Also in:
linux-pwm, lkml
Hi Peter, Am Donnerstag, den 27.10.2016, 13:01 +0300 schrieb Peter Ujfalusi:
Move the checks to select the initial state for the backlight to a new function and document the checks we are doing. At the same time correct the handling of the case when the GPIO is initially configured as input: we need to change the direction of the GPIO to output and set the GPIO to low as the pin was not driven when the GPIO was configured as input.
I think this part should be a separate patch. At least it is a significant enough change to warrant a mention in the subject. And I'm not entirely sure this is better than before. If there happens to be a pull-up on the GPIO (for whatever reason), we might introduce flicker again if the GPIO goes from input (high) to output (low), and back to output (high) again due to FB_BLANK_UNBLANK. regards Philipp
quoted hunk
With the separate function it is going to be easier to fix or improve the initial power state configuration later and it is easier to read the code. Signed-off-by: Peter Ujfalusi <redacted> --- drivers/video/backlight/pwm_bl.c | 54 ++++++++++++++++++++++++++-------------- 1 file changed, 35 insertions(+), 19 deletions(-)diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 12614006211e..74083d880144 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c@@ -192,6 +192,32 @@ static int pwm_backlight_parse_dt(struct device *dev, } #endif +static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) +{ + struct device_node *node = pb->dev->of_node; + + /* Not booted with device tree or no phandle link to the node */ + if (!node || !node->phandle) + return FB_BLANK_UNBLANK; + + /* + * If the driver is probed from the device tree and there is a + * phandle link pointing to the backlight node, it is safe to + * assume that another driver will enable the backlight at the + * appropriate time. Therefore, if it is disabled, keep it so. + */ + + /* if the enable GPIO is disabled, do not enable the backlight */
nitpick: s/if/If/ for consistency.
quoted hunk
+ if (pb->enable_gpio && gpiod_get_value(pb->enable_gpio) = 0) + return FB_BLANK_POWERDOWN; + + /* The regulator is disabled, do not enable the backlight */ + if (!regulator_is_enabled(pb->power_supply)) + return FB_BLANK_POWERDOWN; + + return FB_BLANK_UNBLANK; +} + static int pwm_backlight_probe(struct platform_device *pdev) { struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);@@ -200,7 +226,6 @@ static int pwm_backlight_probe(struct platform_device *pdev) struct backlight_device *bl; struct device_node *node = pdev->dev.of_node; struct pwm_bl_data *pb; - int initial_blank = FB_BLANK_UNBLANK; struct pwm_args pargs; int ret;@@ -267,20 +292,14 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->enable_gpio = gpio_to_desc(data->enable_gpio); } - if (pb->enable_gpio) { - /* - * If the driver is probed from the device tree and there is a - * phandle link pointing to the backlight node, it is safe to - * assume that another driver will enable the backlight at the - * appropriate time. Therefore, if it is disabled, keep it so. - */ - if (node && node->phandle && - gpiod_get_direction(pb->enable_gpio) = GPIOF_DIR_OUT && - gpiod_get_value(pb->enable_gpio) = 0) - initial_blank = FB_BLANK_POWERDOWN; - else - gpiod_direction_output(pb->enable_gpio, 1); - } + /* + * If the GPIO is configured as input, change the direction to output + * and set the GPIO as low since the line was not driven when it was + * configured as input. + */ + if (pb->enable_gpio && + gpiod_get_direction(pb->enable_gpio) = GPIOF_DIR_IN) + gpiod_direction_output_raw(pb->enable_gpio, 0); pb->power_supply = devm_regulator_get(&pdev->dev, "power"); if (IS_ERR(pb->power_supply)) {@@ -288,9 +307,6 @@ static int pwm_backlight_probe(struct platform_device *pdev) goto err_alloc; } - if (node && node->phandle && !regulator_is_enabled(pb->power_supply)) - initial_blank = FB_BLANK_POWERDOWN; - pb->pwm = devm_pwm_get(&pdev->dev, NULL); if (IS_ERR(pb->pwm) && PTR_ERR(pb->pwm) != -EPROBE_DEFER && !node) { dev_err(&pdev->dev, "unable to request PWM, trying legacy API\n");@@ -347,7 +363,7 @@ static int pwm_backlight_probe(struct platform_device *pdev) } bl->props.brightness = data->dft_brightness; - bl->props.power = initial_blank; + bl->props.power = pwm_backlight_initial_power_state(pb); backlight_update_status(bl); platform_set_drvdata(pdev, bl);