Re: [PATCH v20] drm/msm/dpu: Enable quad-pipe for DSC and dual-DSI case

[Dmitry Baryshkov]

On Thu, May 21, 2026 at 05:15:18PM +0800, Jun Nie wrote:
> Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx> 于2026年5月21日周四 01:41写道：
> >
> > On Wed, May 20, 2026 at 04:41:29PM +0300, Dmitry Baryshkov wrote:
> > > On Wed, 15 Apr 2026 11:15:11 +0800, Jun Nie wrote:
> > > > To support high-resolution cases that exceed the width constrain
> > > > or scenarios that surpass the maximum MDP clock rate, additional
> > > > pipes are necessary to enable parallel data processing within
> > > > the width constraints and MDP clock rate.
> > > >
> > > > Expand pipe array size to 4. Request 4 mixers and 4 DSCs for
> > > > high-resolution cases where dual interfaces are enabled for virtual
> > > > plane case. More use cases can be incorporated later if quad-pipe
> > > > capabilities are required.
> > > >
> > > > [...]
> > >
> > > Applied to msm-next, thanks!
> > >
> > > [1/1] drm/msm/dpu: Enable quad-pipe for DSC and dual-DSI case
> > >       https://gitlab.freedesktop.org/lumag/msm/-/commit/218eb06a72bf
> >
> > And I'm going to drop it again.
> >
> > I tested on the SDM845, it tried enabling QUAD_PIPE for the follwing
> > mode, which then broke the display.
> >
> >         mode: "3840x2160": 30 297000 3840 4016 4104 4400 2160 2168 2178 2250 0x40 0x5
> >
> What's the platform? To enable QUAD_PIPE, both virtual plane feature and 2
> real time RT interfaces are needed besides width exceeding the constrain.
> If all conditions in the dpu_crtc_get_topology() are met, why QUAD_PIPE
> cannot be enabled on this platform, any other condition shall be added?

The platform is SDM845 HDK, it should also be reproducible on the RB3
platform, which uses the same chip. I assume the difference is related
to the active vs non-active CTL (which means that QUAD PIPE needs to be
disabled for all platforms before 5.x). I've asked my colleagues to test
quad pipe on other platforms, I'll report on it later.

But it also surprised me that the code selects 4 LMs for the 4k@30 mode.
It should be prefectly working with just 2LMs and 2 rectangles.

> 
> Regards,
> Jun

-- 
With best wishes
Dmitry