Hi, (resent from new email)
On Thu, May 14, 2026 at 2:04 PM Krzysztof Kozlowski <[email protected]> wrote: > > On Sat, May 09, 2026 at 09:00:14PM +0200, Jernej Skrabec wrote: > > From: Jernej Skrabec <[email protected]> > > > > As it turns out, current H616 DE33 binding was written based on > > incomplete understanding of DE33 design. Namely, planes are shared > > resource and not tied to specific mixer, which was the case for previous > > generations of Display Engine (DE3 and earlier). > > > > This means that current DE33 binding doesn't properly reflect HW and > > using it would mean that second mixer (used for second display output) > > can't be supported. > > > > Remove layer register space, which will be represented with additional > > node, and replace it with phandle, which will point to that new, shared > > node. That way, all mixers can share same layers. > > > > There is no user of this binding yet, so changes can be made safely, > > without breaking any backward compatibility. > > There is user. git grep gives me: > drivers/gpu/drm/sun4i/sun8i_mixer.c > > which means this is a released ABI. As I understood, the old code was We held off on merging the DT changes so that we could rework this. I can't find the actual request though. It was probably over IRC. > working fine but just did not support all use cases. Why this cannot be > kept backwards compatible? AFAIK the "planes" block is shared between two display mixers. As the commit message explains, this prevents using the second mixer, since only one of them can claim and map the register space. And on the H700 (which is the same die as the H616 discussed here but with more exposed interfaces), there could actually be a use case for the second mixer. Hope that explains things. ChenYu
