Daniel, On 2018-06-13 18:11, Daniel Thompson wrote: > On 08/05/18 08:04, Peter Ujfalusi wrote: >> The default-on property - or the def_value via legacy pdata) should be >> handled as: >> if it is 1, the backlight must be enabled (kept enabled) >> if it is 0, the backlight must be disabled (kept disabled) >> >> This only works for the case when default-on is set. If it is not set >> then >> the brightness of the backlight is set to 0. Now if the backlight is >> enabled by external driver (graphics) the backlight will stay disabled >> since >> the brightness is configured as 0. The backlight will not turn on. >> >> The correct action at probe time is to configure the props.power to >> FB_BLANK_UNBLANK if we want the backlight on by default or to >> FB_BLANK_POWERDOWN if the backlight should be off by default. >> >> The initial brightness should be set to 1. > > Hmnn... I guess this comes down to the definition of "on" for a binary > > Actually I'm a little worried that backlight already has too many > different behaviors and that this patch introduces another way for them > to be different! > > Is there any mileage in adopting the same approach as PWM backlight for > blank/unblank management as a way to get a flicker free boot? This patch is merely fixing a bug in the driver. > For PWM the default property controls the initial brightness and the > initial power state is unblanked *unless* there is a phandle link to the > node, in which case we inherit whatever the power state the bootloader > had configured before the driver probed. > > Put another way, what happens is we implement > gpio_backlight_initial_power_state() to perform a similar task to > pwm_backlight_initial_power_state(). I agree, but what should we do with the default-on parameter? non DT boot or DT boot, no phandle link: default-on ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN DT boot and phandle link: if the GPIO was enabled by the bootloader: FB_BLANK_UNBLANK if the GIOP was not enabled by the bootloader: FB_BLANK_POWERDOWN I think this will mimic closely what the pwm_backlight_initial_power_state() does. - Péter > > > Daniel. > > >> >> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx> >> --- >> Hi, >> >> for some reason the original patch got lost: >> https://patchwork.kernel.org/patch/9445539/ >> >> But it is still valid, so I'm resending it. >> >> Regards, >> Peter >> >> drivers/video/backlight/gpio_backlight.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/video/backlight/gpio_backlight.c >> b/drivers/video/backlight/gpio_backlight.c >> index e470da95d806..904a4462cefe 100644 >> --- a/drivers/video/backlight/gpio_backlight.c >> +++ b/drivers/video/backlight/gpio_backlight.c >> @@ -142,7 +142,9 @@ static int gpio_backlight_probe(struct >> platform_device *pdev) >> return PTR_ERR(bl); >> } >> - bl->props.brightness = gbl->def_value; >> + bl->props.power = gbl->def_value ? FB_BLANK_UNBLANK : >> FB_BLANK_POWERDOWN; >> + bl->props.brightness = 1; >> + >> backlight_update_status(bl); >> platform_set_drvdata(pdev, bl); >> > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
