[PATCH v1] drm/i915/dp: Modify DP lane count from DPCD reading

[Jani Nikula]

On Fri, 28 Jun 2024, Ben Kao <ben.kao at intel.com> wrote:
> We found that the external monitor would be failed to display
> when hot-plug with dual Type-C USB cable on Dell WD19DC dock.
> Due to the host would receive 2 lanes setting when the first HPD,
> then receive 4 lanes setting later, but the host only sets 2 lanes
> DP and skips to set 4 lanes DP. I modify DP lane count if the
> current DP lane count is not the same as DPCD reading.
>
> Signed-off-by: Ben Kao <ben.kao at intel.com>

Please file a bug according to [1].

BR,
Jani.

[1] https://drm.pages.freedesktop.org/intel-docs/how-to-file-i915-bugs.html


> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 5b3b6ae1e3d7..a9b9023c6744 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -5545,6 +5545,12 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
>  	if (!intel_dp_get_dpcd(intel_dp))
>  		return connector_status_disconnected;
>  
> +	/* lanes count changed */
> +	if (intel_dp->lane_count != drm_dp_max_lane_count(intel_dp->dpcd)) {
> +		intel_dp->lane_count = drm_dp_max_lane_count(intel_dp->dpcd);
> +		return connector_status_disconnected;
> +	}
> +
>  	intel_dp->mst_detect = intel_dp_mst_detect(intel_dp);
>  
>  	/* if there's no downstream port, we're done */

-- 
Jani Nikula, Intel