Re: [PATCH v4] drm: shmobile: Fix white screen after resume when LCDC is stopped

[Wolfram Sang <wsa+renesas@sang-engineering.com>]

On Tue, Jul 07, 2026 at 04:30:04PM +0700, phucduc.bui@gmail.com wrote:
> From: bui duc phuc <phucduc.bui@gmail.com>
> 
> The LCDC on R8A7740 may show a completely white screen after resuming
> from suspend (s2idle or s2ram).
> 
> After resume, both Set A and Set B registers are reset to 0. As the
> Frame End interrupt is not generated while the controller is stopped
> (DO=0), the hardware register switching mechanism is not triggered.
> Consequently, Set A remains at 0x00000000 even though a valid Start
> Address is written to Set B, resulting in a white screen.
> 
> This is a timing-dependent race condition. In some configurations,
> debug options slow down the resume path enough for a Frame End
> interrupt to occur, which can mask the issue.
> 
> Fix this by priming both register sets with the Start Address while the
> controller is stopped, ensuring a valid base address is available
> immediately after resume.
> 
> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Signed-off-by: bui duc phuc <phucduc.bui@gmail.com>
> ---
> 
> Note:
> It was originally posted in March and has already received both 
> Reviewed-by and Tested-by tags. I'm resending it to bring it back 
> to attention in case it was overlooked.
> 
> Changes in v4:
>  - No functional changes.
>  - Resend.

Still not upstream? Who is the person to pick this up? This is a
valuable fix we surely want to have.