Re: [Intel-gfx] [PATCH 2/2] drm/dp: Drop open-coded drm_dp_is_branch() in drm_dp_read_downstream_info()

[Ville Syrjälä]

On Fri, Apr 30, 2021 at 06:34:28PM -0400, Lyude Paul wrote:
> Noticed this while fixing another issue in drm_dp_read_downstream_info(),
> the open coded DP_DOWNSTREAMPORT_PRESENT check here just duplicates what we
> already do in drm_dp_is_branch(), so just get rid of it.
> 
> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 27c8c5bdf7d9..0f84df8798ab 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -677,9 +677,7 @@ int drm_dp_read_downstream_info(struct drm_dp_aux *aux,
>  	memset(downstream_ports, 0, DP_MAX_DOWNSTREAM_PORTS);
>  
>  	/* No downstream info to read */
> -	if (!drm_dp_is_branch(dpcd) ||
> -	    dpcd[DP_DPCD_REV] < DP_DPCD_REV_10 ||
> -	    !(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT))
> +	if (!drm_dp_is_branch(dpcd) || dpcd[DP_DPCD_REV] < DP_DPCD_REV_10)

BTW that DPCD_REV check looks rather wrong.

Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>

>  		return 0;
>  
>  	/* Some branches advertise having 0 downstream ports, despite also advertising they have a
> -- 
> 2.30.2
> 
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-- 
Ville Syrjälä
Intel