Re: Re : Re: Commit 76c2ff3e broke backlight on Chromebook snow
Hi, On Sat, 23 Oct 2021 at 03:23, Dario Binacchi wrote: > > Hi Guillaume, > > > Il 22/10/2021 14:34 Guillaume GARDET ha scritto: > > > > > > Hi Dario, > > > > - Dario Binacchi a écrit : > > > Hi Guillaume, > > > > > > > Il 21/10/2021 16:47 Guillaume GARDET ha > > > > scritto: > > > > > > > > > > > > Hi, > > > > > > > > Commit 76c2ff3e [0] broke backlight on Chromebook snow. > > > > A revert on top of 2021.10 restores the backlight. > > > > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to > > > > fix this? > > > > > > Is it possible that max_level is equal to min_level and therefore division > > > by zero is done? > > > > I do not think so, because u-boot does not crash and the DTS file has > > multiple levels: > > https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/exynos5250-snow.dts#L243 > > > > I think the problem occurs when 'cur_level == max_level', which is also the > > default value in the DTS. > > If I change the default-brightness-level to 6 (instead of 7), then the > > backlight works again, which would confirm the assumption above. > > I have set the default-brightness-level to max-level on my beaglebone board > but the backlight works the same. > I didn't see any difference. I got this running in my lab now and sent a possible fix. Regards, Simon > > Thanks and regards > Dario > > > pwm_backlight_set_brightness seems to set cur_level to max value by > > default. Maybe the driver thinks there is nothing to do, since current > > level is also the desired level? [..]
Re: Commit 76c2ff3e broke backlight on Chromebook snow
Hi, On Fri, 22 Oct 2021 at 05:38, Dario Binacchi wrote: > > Hi Guillaume, > > > Il 21/10/2021 16:47 Guillaume GARDET ha scritto: > > > > > > Hi, > > > > Commit 76c2ff3e [0] broke backlight on Chromebook snow. > > A revert on top of 2021.10 restores the backlight. > > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix > > this? > > Is it possible that max_level is equal to min_level and therefore division > by zero is done?' I got this running in my lab now and sent a possible fix. Regards, Simon
Re: Re : Re: Commit 76c2ff3e broke backlight on Chromebook snow
Hi Guillaume, > Il 22/10/2021 14:34 Guillaume GARDET ha scritto: > > > Hi Dario, > > - Dario Binacchi a écrit : > > Hi Guillaume, > > > > > Il 21/10/2021 16:47 Guillaume GARDET ha > > > scritto: > > > > > > > > > Hi, > > > > > > Commit 76c2ff3e [0] broke backlight on Chromebook snow. > > > A revert on top of 2021.10 restores the backlight. > > > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix > > > this? > > > > Is it possible that max_level is equal to min_level and therefore division > > by zero is done? > > I do not think so, because u-boot does not crash and the DTS file has > multiple levels: > https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/exynos5250-snow.dts#L243 > > I think the problem occurs when 'cur_level == max_level', which is also the > default value in the DTS. > If I change the default-brightness-level to 6 (instead of 7), then the > backlight works again, which would confirm the assumption above. I have set the default-brightness-level to max-level on my beaglebone board but the backlight works the same. I didn't see any difference. Thanks and regards Dario > pwm_backlight_set_brightness seems to set cur_level to max value by default. > Maybe the driver thinks there is nothing to do, since current level is also > the desired level? > > > Cheers, > Guillaume > > > > > > Thanks and regards, > > Dario > > > > > > Cheers, > > > Guillaume
Re : Re: Commit 76c2ff3e broke backlight on Chromebook snow
Hi Dario, - Dario Binacchi a écrit : > Hi Guillaume, > > > Il 21/10/2021 16:47 Guillaume GARDET ha scritto: > > > > > > Hi, > > > > Commit 76c2ff3e [0] broke backlight on Chromebook snow. > > A revert on top of 2021.10 restores the backlight. > > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix > > this? > > Is it possible that max_level is equal to min_level and therefore division > by zero is done? I do not think so, because u-boot does not crash and the DTS file has multiple levels: https://source.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/exynos5250-snow.dts#L243 I think the problem occurs when 'cur_level == max_level', which is also the default value in the DTS. If I change the default-brightness-level to 6 (instead of 7), then the backlight works again, which would confirm the assumption above. pwm_backlight_set_brightness seems to set cur_level to max value by default. Maybe the driver thinks there is nothing to do, since current level is also the desired level? Cheers, Guillaume > > Thanks and regards, > Dario > > > > Cheers, > > Guillaume
Re: Commit 76c2ff3e broke backlight on Chromebook snow
Hi Guillaume, > Il 21/10/2021 16:47 Guillaume GARDET ha scritto: > > > Hi, > > Commit 76c2ff3e [0] broke backlight on Chromebook snow. > A revert on top of 2021.10 restores the backlight. > Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix > this? Is it possible that max_level is equal to min_level and therefore division by zero is done? Thanks and regards, Dario > > Cheers, > Guillaume
Commit 76c2ff3e broke backlight on Chromebook snow
Hi, Commit 76c2ff3e [0] broke backlight on Chromebook snow. A revert on top of 2021.10 restores the backlight. Not sure why it breaks on Chromebook snow yet. Dario, any idea how to fix this? Cheers, Guillaume
