From: Daniel Thompson daniel.thompson@linaro.org
stable inclusion from stable-5.10.65 commit 5866b1175df086cb0b3451b11ad88667b53d4018 bugzilla: 182361 https://gitee.com/openeuler/kernel/issues/I4EH3U
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 79fad92f2e596f5a8dd085788a24f540263ef887 upstream.
Currently there are (at least) two problems in the way pwm_bl starts managing the enable_gpio pin. Both occur when the backlight is initially off and the driver finds the pin not already in output mode and, as a result, unconditionally switches it to output-mode and asserts the signal.
Problem 1: This could cause the backlight to flicker since, at this stage in driver initialisation, we have no idea what the PWM and regulator are doing (an unconfigured PWM could easily "rest" at 100% duty cycle).
Problem 2: This will cause us not to correctly honour the post_pwm_on_delay (which also risks flickers).
Fix this by moving the code to configure the GPIO output mode until after we have examines the handover state. That allows us to initialize enable_gpio to off if the backlight is currently off and on if the backlight is on.
Cc: stable@vger.kernel.org Reported-by: Marek Vasut marex@denx.de Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Acked-by: Marek Vasut marex@denx.de Tested-by: Marek Vasut marex@denx.de Signed-off-by: Lee Jones lee.jones@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com --- drivers/video/backlight/pwm_bl.c | 54 +++++++++++++++++--------------- 1 file changed, 28 insertions(+), 26 deletions(-)
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index dfc760830eb9..1cf924f3aecc 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -417,6 +417,33 @@ static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data) static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) { struct device_node *node = pb->dev->of_node; + bool active = true; + + /* + * If the enable GPIO is present, observable (either as input + * or output) and off then the backlight is not currently active. + * */ + if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0) + active = false; + + if (!regulator_is_enabled(pb->power_supply)) + active = false; + + if (!pwm_is_enabled(pb->pwm)) + active = false; + + /* + * Synchronize the enable_gpio with the observed state of the + * hardware. + */ + if (pb->enable_gpio) + gpiod_direction_output(pb->enable_gpio, active); + + /* + * Do not change pb->enabled here! pb->enabled essentially + * tells us if we own one of the regulator's use counts and + * right now we do not. + */
/* Not booted with device tree or no phandle link to the node */ if (!node || !node->phandle) @@ -428,20 +455,7 @@ static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) * 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 */ - if (pb->enable_gpio && gpiod_get_value_cansleep(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; - - /* The PWM is disabled, keep it like this */ - if (!pwm_is_enabled(pb->pwm)) - return FB_BLANK_POWERDOWN; - - return FB_BLANK_UNBLANK; + return active ? FB_BLANK_UNBLANK: FB_BLANK_POWERDOWN; }
static int pwm_backlight_probe(struct platform_device *pdev) @@ -494,18 +508,6 @@ static int pwm_backlight_probe(struct platform_device *pdev) goto err_alloc; }
- /* - * If the GPIO is not known to be already configured as output, that - * is, if gpiod_get_direction returns either 1 or -EINVAL, change the - * direction to output and set the GPIO as active. - * Do not force the GPIO to active when it was already output as it - * could cause backlight flickering or we would enable the backlight too - * early. Leave the decision of the initial backlight state for later. - */ - if (pb->enable_gpio && - gpiod_get_direction(pb->enable_gpio) != 0) - gpiod_direction_output(pb->enable_gpio, 1); - pb->power_supply = devm_regulator_get(&pdev->dev, "power"); if (IS_ERR(pb->power_supply)) { ret = PTR_ERR(pb->power_supply);