| Message ID | 20240202095044.1980696-1-m.szyprowski@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ARM: multi_v7_defconfig: Enable BACKLIGHT_CLASS_DEVICE | expand |
Hi Marek, On Fri, Feb 2, 2024 at 10:51 AM Marek Szyprowski <m.szyprowski@samsung.com> wrote: > Commit 72fee6b0a3a4 ("fbdev: Restrict FB_SH_MOBILE_LCDC to SuperH") > disabled availablity of the SH_MOBILE_LCDC driver on the RENESAS arch. > This innocent change has a significant side-effect on the ARM's > multi_v7_defconfig, because FB_BACKLIGHT symbol is no longer selected, > what in turn leaves BACKLIGHT_CLASS_DEVICE symbol selected only as > a module. The latter disables some backlight related code in the DRM Oops, sorry for that. > core, because the DRM core is set to be compiled-in in this defconfig. > This leaves all DRM display panels without integrated backlight control, > even if the needed modules have been properly loaded and probed. Hmm, that's bad. Is there any way to fix this in DRM? A quick grep shows that DRM is using the full monty of IS_{BUILTIN,ENABLED,MODULE,REACHABLE}(CONFIG_BACKLIGHT_CLASS_DEVICE). Probably not all of them are in perfect sync? Several DRM drivers do select BACKLIGHT_CLASS_DEVICE, but if that does not work in the modular case, it should be fixed. > Fix this by selecting BACKLIGHT_CLASS_DEVICE to be compiled-in in > multi_v7_defconfig. > > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Sounds like a good interim solution. Acked-by: Geert Uytterhoeven <geert+renesas@glider.be> Gr{oetje,eeting}s, Geert
On Fri, Feb 2, 2024, at 11:07, Geert Uytterhoeven wrote: > On Fri, Feb 2, 2024 at 10:51 AM Marek Szyprowski <m.szyprowski@samsung.com> wrote: >> core, because the DRM core is set to be compiled-in in this defconfig. >> This leaves all DRM display panels without integrated backlight control, >> even if the needed modules have been properly loaded and probed. > > Hmm, that's bad. > > Is there any way to fix this in DRM? > A quick grep shows that DRM is using the full monty of > IS_{BUILTIN,ENABLED,MODULE,REACHABLE}(CONFIG_BACKLIGHT_CLASS_DEVICE). > Probably not all of them are in perfect sync? The IS_REACHABLE() ones are almost certainly bugs, as are the 'select BACKLIGHT_CLASS_DEVICE' ones we have in drivers/gpu. > Several DRM drivers do select BACKLIGHT_CLASS_DEVICE, but if that > does not work in the modular case, it should be fixed. The select should do the right thing in principle, but mixing it with depends is what causes circular dependencies. Unfortunately trying to fix it likely also causes those, but I think it's worth revisiting. It should be possible to change it like this: - change all DRM drivers that require the class to 'depends on BACKLIGHT_CLASS_DEVICE' - change all those drivers that can optionally use it to 'depends on BACKLIGHT_CLASS_DEVICE || !BACKLIGHT_CLASS_DEVICE' to avoid the dependency on a loadable module - Make BACKLIGHT_CLASS_DEVICE itself default to 'DRM' in order to avoid regressions in defconfig files but still make it possible to turn it off. >> Fix this by selecting BACKLIGHT_CLASS_DEVICE to be compiled-in in >> multi_v7_defconfig. >> >> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> > > Sounds like a good interim solution. > > Acked-by: Geert Uytterhoeven <geert+renesas@glider.be> Thanks, I've applied it to the soc/defconfig branch now. Arnd
diff --git a/arch/arm/configs/multi_v7_defconfig b/arch/arm/configs/multi_v7_defconfig index 8f7445729cd0..b2955dcb5a53 100644 --- a/arch/arm/configs/multi_v7_defconfig +++ b/arch/arm/configs/multi_v7_defconfig @@ -777,6 +777,7 @@ CONFIG_FB_EFI=y CONFIG_FB_WM8505=y CONFIG_FB_SH_MOBILE_LCDC=y CONFIG_FB_SIMPLE=y +CONFIG_BACKLIGHT_CLASS_DEVICE=y CONFIG_BACKLIGHT_PWM=y CONFIG_BACKLIGHT_AS3711=y CONFIG_BACKLIGHT_GPIO=y
Commit 72fee6b0a3a4 ("fbdev: Restrict FB_SH_MOBILE_LCDC to SuperH") disabled availablity of the SH_MOBILE_LCDC driver on the RENESAS arch. This innocent change has a significant side-effect on the ARM's multi_v7_defconfig, because FB_BACKLIGHT symbol is no longer selected, what in turn leaves BACKLIGHT_CLASS_DEVICE symbol selected only as a module. The latter disables some backlight related code in the DRM core, because the DRM core is set to be compiled-in in this defconfig. This leaves all DRM display panels without integrated backlight control, even if the needed modules have been properly loaded and probed. Fix this by selecting BACKLIGHT_CLASS_DEVICE to be compiled-in in multi_v7_defconfig. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- arch/arm/configs/multi_v7_defconfig | 1 + 1 file changed, 1 insertion(+)