Re: [PATCH 0/3] Add support for databus widen mode

[Dmitry Baryshkov]

On 14/06/2023 04:57, Jessica Zhang wrote:
> DPU 5.x+ and DSI 6G 2.5.x+ support a databus-widen mode that allows for
> more compressed data to be transferred per pclk.
>
> This series adds support for enabling this feature for both DPU and DSI
> by doing the following:
>
> 1. Add a DPU_INTF_DATABUS_WIDEN feature flag
> 2. Add a DPU INTF op to set the DATABUS_WIDEN register
> 3. Set the DATABUS_WIDEN register and do the proper hdisplay
>     calculations in DSI when applicable

As I was writing the documentation patch, another thought stroke me wrt 
this patchset. Could you please add a check to DSI's mode_valid 
disallowing all modes if DSI_BPP > 8 & !widebus. Technically this check 
does not filter modes per se, but in my opinion ending up with empty 
modes list would be a better user experience compared to having a list 
of modes, from which none can be selected.

And if we ever get dynamic mode/dsc_config setup, this would allow us to 
filter unsupported modes via their DSC confiuration.

Abhinav, I remember, that you told me that adding drm_dsc_config to drm 
modes was forbidden already. However this looks like a valid reason to 
maybe restart the discussion: we want to filter modes basing on the 
corresponding DSC data rather than allowing the mode in mode_valid() and 
then failing it in the atomic_check().

> Note: This series will only enable the databus-widen mode for command
> mode as we are currently unable to validate it on video mode.
>
> Depends on: "Add DSC v1.2 Support for DSI" [1]
>
> [1] https://patchwork.freedesktop.org/series/117219/
>
> Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>

Nit: there is no need to sign-off the cover letters.

> ---
> Jessica Zhang (3):
>        drm/msm/dpu: Add DPU_INTF_DATABUS_WIDEN feature flag for DPU >= 5.0
>        drm/msm/dpu: Set DATABUS_WIDEN on command mode encoders
>        drm/msm/dsi: Enable DATABUS_WIDEN for DSI command mode
>
>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c |  3 +++
>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c       |  3 ++-
>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h       |  2 ++
>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c          | 12 ++++++++++++
>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.h          |  3 +++
>   drivers/gpu/drm/msm/dsi/dsi.xml.h                    |  1 +
>   drivers/gpu/drm/msm/dsi/dsi_host.c                   | 19 ++++++++++++++++++-
>   7 files changed, 41 insertions(+), 2 deletions(-)
> ---
> base-commit: 1981c2c0c05f5d7fe4d4552d4f352cb46840e51e
> change-id: 20230525-add-widebus-support-f785546ee751
>
> Best regards,

--
With best wishes
Dmitry