[PATCH] drm/amd/display: Modify display link stream setup sequence.

[Kazlauskas, Nicholas]

On 2019-10-17 12:28 a.m., Liu, Zhan wrote:
> From: Zhan Liu <zhan.liu at amd.com>
> 
> [Why]
> When a specific kind of connector is detected,
> DC needs to set the attribute of the stream.
> This step needs to be done before enabling link,
> or some bugs (e.g. display won't light up)
> will be observed.
> 
> [How]
> Setting the attribute of the stream first, then
> enabling stream.
> 
> Signed-off-by: Zhan Liu <zhan.liu at amd.com>

NAK:

1. It's difficult to understand what issue this change is attempting to 
solve and why it actually does it. Specifics would help here.

2. It affects a common code path for all ASICs which has been tested and 
known to be working correctly for those test cases.

3. The description is incorrect - the link enable/stream enable were 
both previously happening after the stream setup. What's changed in the 
patch is the link enable now happens before the link setup.

Both of these calls internally go through the command table to VBIOS so 
what behavior differences you're seeing may be caused by the input 
parameters to the ATOM_ENCODER_CMD_STREAM_SETUP or 
TRANSMITTER_CONTROL_ENABLE commands or the actual execution of those 
commands.

Nicholas Kazlauskas

> ---
>   drivers/gpu/drm/amd/display/dc/core/dc_link.c | 20 +++++++++----------
>   1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link.c b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> index fb18681b502b..713caab82837 100644
> --- a/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> +++ b/drivers/gpu/drm/amd/display/dc/core/dc_link.c
> @@ -2745,16 +2745,6 @@ void core_link_enable_stream(
>                          dc_is_virtual_signal(pipe_ctx->stream->signal))
>                  return;
> 
> -       if (!dc_is_virtual_signal(pipe_ctx->stream->signal)) {
> -               stream->link->link_enc->funcs->setup(
> -                       stream->link->link_enc,
> -                       pipe_ctx->stream->signal);
> -               pipe_ctx->stream_res.stream_enc->funcs->setup_stereo_sync(
> -                       pipe_ctx->stream_res.stream_enc,
> -                       pipe_ctx->stream_res.tg->inst,
> -                       stream->timing.timing_3d_format != TIMING_3D_FORMAT_NONE);
> -       }
> -
>          if (dc_is_dp_signal(pipe_ctx->stream->signal))
>                  pipe_ctx->stream_res.stream_enc->funcs->dp_set_stream_attribute(
>                          pipe_ctx->stream_res.stream_enc,
> @@ -2841,6 +2831,16 @@ void core_link_enable_stream(
>                                          CONTROLLER_DP_TEST_PATTERN_VIDEOMODE,
>                                          COLOR_DEPTH_UNDEFINED);
> 
> +               if (!dc_is_virtual_signal(pipe_ctx->stream->signal)) {
> +                       stream->link->link_enc->funcs->setup(
> +                               stream->link->link_enc,
> +                               pipe_ctx->stream->signal);
> +                       pipe_ctx->stream_res.stream_enc->funcs->setup_stereo_sync(
> +                               pipe_ctx->stream_res.stream_enc,
> +                               pipe_ctx->stream_res.tg->inst,
> +                               stream->timing.timing_3d_format != TIMING_3D_FORMAT_NONE);
> +               }
> +
>   #ifdef CONFIG_DRM_AMD_DC_DSC_SUPPORT
>                  if (pipe_ctx->stream->timing.flags.DSC) {
>                          if (dc_is_dp_signal(pipe_ctx->stream->signal) ||
> --
> 2.17.1
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