linux-kernel - Re: [PATCH 1/3] drm/msm/dpu: Add DPU_INTF_DATABUS

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Message-ID: <ycgei43x4kfmjk7g7gbeglehtiiinfbqmrjbdzcy56frxbtd2z@yk2f5kgrkbrt>
Date:   Wed, 14 Jun 2023 14:23:36 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Jessica Zhang <quic_jesszhan@...cinc.com>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, quic_abhinavk@...cinc.com,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] drm/msm/dpu: Add DPU_INTF_DATABUS_WIDEN feature flag
 for DPU >= 5.0

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@...cinc.com>
> >> ---
> >>   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.

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.

> > 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.

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?

- Marijn