Re: [Freedreno] [PATCH 1/3] drm/msm/dpu: Add DPU_INTF_DATABUS_WIDEN feature flag for DPU >= 5.0

[Abhinav Kumar]

On 6/14/2023 12:54 PM, Abhinav Kumar wrote:
> On 6/14/2023 12:35 PM, Abhinav Kumar wrote:
> > On 6/14/2023 5:23 AM, Marijn Suijten wrote:
> > > On 2023-06-14 15:01:59, Dmitry Baryshkov wrote:
> > > > On 14/06/2023 14:42, Marijn Suijten wrote:
> > > > > On 2023-06-13 18:57:11, Jessica Zhang wrote:
> > > > > > DPU 5.x+ supports a databus widen mode that allows more data to be 
> > > > > > sent
> > > > > > per pclk. Enable this feature flag on all relevant chipsets.
> > > > > >
> > > > > > Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
> > > > > > ---
> > > > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c | 3 ++-
> > > > > >    drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h | 2 ++
> > > > > >    2 files changed, 4 insertions(+), 1 deletion(-)
> > > > > >
> > > > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c 
> > > > > > b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
> > > > > > index 36ba3f58dcdf..0be7bf0bfc41 100644
> > > > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
> > > > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
> > > > > > @@ -103,7 +103,8 @@
> > > > > >        (BIT(DPU_INTF_INPUT_CTRL) | \
> > > > > >         BIT(DPU_INTF_TE) | \
> > > > > >         BIT(DPU_INTF_STATUS_SUPPORTED) | \
> > > > > > -     BIT(DPU_DATA_HCTL_EN))
> > > > > > +     BIT(DPU_DATA_HCTL_EN) | \
> > > > > > +     BIT(DPU_INTF_DATABUS_WIDEN))
> > > > >
> > > > > This doesn't work.  DPU 5.0.0 is SM8150, which has DSI 6G 2.3.  In the
> > > > > last patch for DSI you state and enable widebus for DSI 6G 2.5+ only,
> > > > > meaning DPU and DSI are now desynced, and the output is completely
> > > > > corrupted.

I looked at the internal docs and also this change. This change is 
incorrect because this will try to enable widebus for DPU >= 5.0 and DSI 
>= 2.5

That was not the intended right condition as thats not what the docs say.

We should enable for DPU >= 7.0 and DSI >= 2.5

Is there any combination where this compatibility is broken? That would 
be the strange thing for me ( not DPU 5.0 and DSI 2.5 as that was incorrect)

Part of this confusion is because of catalog macro re-use again.

This series is a good candidate and infact I think we should only do 
core_revision based check on DPU and DSI to avoid bringing the catalog 
mess into this.

> > > Tested this on SM8350 which actually has DSI 2.5, and it is also
> > > corrupted with this series so something else on this series might be
> > > broken.
>
> Missed this response. That seems strange.
>
> This series was tested on SM8350 HDK with a command mode panel.
>
> We will fix the DPU-DSI handshake and post a v2 but your issue needs 
> investigation in parallel.
>
> So another bug to track that would be great.
>
> > > > > Is the bound in dsi_host wrong, or do DPU and DSI need to communicate
> > > > > when widebus will be enabled, based on DPU && DSI supporting it?
> > > >
> > > > I'd prefer to follow the second approach, as we did for DP. DPU asks 
> > > > the
> > > > actual video output driver if widebus is to be enabled.
> >
> > I was afraid of this. This series was made on an assumption that the 
> > DPU version of widebus and DSI version of widebus would be compatible 
> > but looks like already SM8150 is an outlier.
> >
> > Yes, I think we have to go with second approach.
> >
> > DPU queries DSI if it supports widebus and enables it.
> >
> > Thanks for your responses. We will post a v2.
> >
> > > Doesn't it seem very strange that DPU 5.x+ comes with a widebus feature,
> > > but the DSI does not until two revisions later?  Or is this available on
> > > every interface, but only for a different (probably DP) encoder block?
> >
> > Yes its strange.

I have clarified this above. Its not strange but appeared strange 
because we were checking wrong conditions.


> > > - Marijn