Hello Huacai, Thanks for the patch. On 5/21/22 15:41, Huacai Chen wrote: > Consider a configuration like this: > 1, efifb (or simpledrm) is built-in; > 2, a native display driver (such as radeon) is also built-in. > As mentioned in the other thread, this is not a common configuration. Usually the native display drivers are built as a module and only the generic drivers that use a firmware-provided firmware for scanout are built-in the kernel image. > Because efifb, radeon and sysfb are all in device_initcall() level, the > order in practise is like this: > > efifb registered at first, but no "efi-framebuffer" device yet. radeon > registered later, and /dev/fb0 created. sysfb_init() comes at last, it > registers "efi-framebuffer" and then causes an error message "efifb: a > framebuffer is already registered". Make sysfb_init() to be subsys_ > initcall_sync() can avoid this. But Javier Martinez Canillas has a more > general solution. > You are talking about "[PATCH v5 0/7] Fix some races between sysfb device registration and drivers probe", but unfortunately that approach was not as general as needed, see: https://lore.kernel.org/all/026b1c6d-c258-fa88-ed08-d1b5784c95b0@xxxxxxx/ I need to go back to that series but I'm not sure when will have the time. > However, this patch still makes sense because it can make the screen > display as early as possible (We cannot move to subsys_initcall, since > sysfb_init() should be executed after PCI enumeration). > Indeed. I agree that makes sense to move the platform device registration early. As you mentioned this only solve some of the issues since we don't know when the _driver_ is going to be registered. But at least we ensure that by the time built-in drivers are registered, the platform device is already there to match. Bringing the display output as early as possible. > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx> > --- > drivers/firmware/sysfb.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/firmware/sysfb.c b/drivers/firmware/sysfb.c > index 2bfbb05f7d89..aecf91517e54 100644 > --- a/drivers/firmware/sysfb.c > +++ b/drivers/firmware/sysfb.c > @@ -80,4 +80,4 @@ static __init int sysfb_init(void) > } > > /* must execute after PCI subsystem for EFI quirks */ > -device_initcall(sysfb_init); > +subsys_initcall_sync(sysfb_init); I would make the comment here more verbose. Mentioning that PCI enumeration happens in the subsys_initcall() init call level and so is safe to register this at subsys_initcall_sync(), which happens after or something like that. Probably would be good to also mention the same in the patch description. Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx> -- Best regards, Javier Martinez Canillas Linux Engineering Red Hat
