Re: [PATCH v3 2/4] drm/msm/dpu: Enable widebus for DSI INTF

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On 08/08/2023 00:40, Jessica Zhang wrote:


On 8/2/2023 11:20 AM, Dmitry Baryshkov wrote:
On Wed, 2 Aug 2023 at 21:09, Jessica Zhang <quic_jesszhan@xxxxxxxxxxx> wrote:

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
index df88358e7037..dace6168be2d 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c
@@ -69,8 +69,10 @@ static void _dpu_encoder_phys_cmd_update_intf_cfg(
                                 phys_enc->hw_intf,
                                 phys_enc->hw_pp->idx);

-       if (intf_cfg.dsc != 0)
+       if (intf_cfg.dsc != 0) {
                 cmd_mode_cfg.data_compress = true;
+               cmd_mode_cfg.wide_bus_en = dpu_encoder_is_widebus_enabled(phys_enc->parent);
+       }

This embeds the knowledge that a wide bus can only be enabled when DSC
is in use. Please move the wide_bus_en assignment out of conditional
code.

Wide bus for DSI will only be enabled if DSC is enabled, so this is technically not wrong, as DP will use the video mode path.



         if (phys_enc->hw_intf->ops.program_intf_cmd_cfg)
phys_enc->hw_intf->ops.program_intf_cmd_cfg(phys_enc->hw_intf, &cmd_mode_cfg); diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
index 8ec6505d9e78..dc6f3febb574 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_intf.c
@@ -521,6 +521,9 @@ static void dpu_hw_intf_program_intf_cmd_cfg(struct dpu_hw_intf *ctx,

This function is only enabled for DPU >= 7.0, while IIRC wide bus can
be enabled even for some of the earlier chipsets.

The command mode path is only called for DSI, which only supports wide bus for DPU 7.0+.

After second consideration, let's ignore this part, as wide bus will only be enabled for DSI / CMD after 7.0. If we ever have SoC that has CMD + wide_bus earlier than 5.0, we can reconsider this code pice.

Can you please add a comment that the register itself is present earlier (5.0), but it doesn't have to be programmed since the flags will not be set anyway.



         if (cmd_mode_cfg->data_compress)
                 intf_cfg2 |= INTF_CFG2_DCE_DATA_COMPRESS;

+       if (cmd_mode_cfg->wide_bus_en)
+               intf_cfg2 |= INTF_CFG2_DATABUS_WIDEN;
+
         DPU_REG_WRITE(&ctx->hw, INTF_CONFIG2, intf_cfg2);
  }




--
With best wishes
Dmitry




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