On Tue, Jul 04, 2023 at 04:31:51PM +0100, Måns Rullgård wrote: > Daniel Thompson <[email protected]> writes: > > > On Tue, Jul 04, 2023 at 03:07:50PM +0100, Mans Rullgard wrote: > >> The condition for the initial power state based on the default > >> brightness value is reversed. Fix it. > >> > >> Fixes: ae232e45acf9 ("backlight: add led-backlight driver") > >> Signed-off-by: Mans Rullgard <[email protected]> > >> --- > >> drivers/video/backlight/led_bl.c | 4 ++-- > >> 1 file changed, 2 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/video/backlight/led_bl.c > >> b/drivers/video/backlight/led_bl.c > >> index 3259292fda76..28e83618a296 100644 > >> --- a/drivers/video/backlight/led_bl.c > >> +++ b/drivers/video/backlight/led_bl.c > >> @@ -200,8 +200,8 @@ static int led_bl_probe(struct platform_device *pdev) > >> props.type = BACKLIGHT_RAW; > >> props.max_brightness = priv->max_brightness; > >> props.brightness = priv->default_brightness; > >> - props.power = (priv->default_brightness > 0) ? FB_BLANK_POWERDOWN : > >> - FB_BLANK_UNBLANK; > >> + props.power = (priv->default_brightness > 0) ? FB_BLANK_UNBLANK : > >> + FB_BLANK_POWERDOWN; > > > > The logic was wrong before but I think will still be wrong after the > > change too (e.g. the bogus logic is probably avoiding backlight flicker > > in some use cases). > > > > The logic here needs to be similar to what pwm_bl.c implements in > > pwm_backlight_initial_power_state(). Whilst it might be better > > to implement this in led_bl_get_leds() let me show what I mean > > in code that fits in the current line: > > > > /* > > * Activate the backlight if the LEDs are already lit *or* > > * there is no phandle link (meaning the backlight power > > * state cannot be synced with the display state). > > */ > > props.power = (active_at_boot || !dev->node->phandle) ? > > FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN; > > > > Note that active_at_boot is not the same as (priv->default_brightness > 0) > > since the value read by led_bl_get_leds() can be clobbered when we > > parse the properties. > > Am I understanding correctly that the code should be using the > default_brightness value as set by led_bl_get_leds() to determine the > initial power state, not whatever default value the devicetree provides?
Yes. The devicetree allows us to specify a default brightness but the DT value cannot not be used to decide if the backlight has already been lit up. Daniel.
