[Intel-gfx] [PATCH 1/2] drm/i915: Flatten intel_dp_check_mst_status() a bit

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Fri, 2020-04-17 at 18:27 +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Make intel_dp_check_mst_status() somewhat legible by humans.
> 
> Note that the return value of drm_dp_mst_hpd_irq() is always
> either 0 or -ENOMEM, and we never did anything with the latter
> so we can just ignore the whole thing.
> 
> We can also get rid of the direct drm_dp_mst_topology_mgr_set_mst(false)
> call since returning -EINVAL causes the caller to do the very same call
> for us.
> 
> Cc: Lyude Paul <lyude at redhat.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 88 ++++++++++++-------------
>  1 file changed, 41 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> b/drivers/gpu/drm/i915/display/intel_dp.c
> index 48397b2c08cf..4d4898db38e9 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -5628,61 +5628,55 @@ static int
>  intel_dp_check_mst_status(struct intel_dp *intel_dp)
>  {
>  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> -	bool bret;
>  
> -	if (intel_dp->is_mst) {
> -		u8 esi[DP_DPRX_ESI_LEN] = { 0 };
> -		int ret = 0;
> +	if (!intel_dp->is_mst)
> +		return -EINVAL;
> +
> +	WARN_ON_ONCE(intel_dp->active_mst_links < 0);
> +
> +	for (;;) {
> +		u8 esi[DP_DPRX_ESI_LEN] = {};
> +		bool bret, handled;
>  		int retry;
> -		bool handled;
>  
> -		WARN_ON_ONCE(intel_dp->active_mst_links < 0);
>  		bret = intel_dp_get_sink_irq_esi(intel_dp, esi);
> -go_again:
> -		if (bret == true) {
> -
> -			/* check link status - esi[10] = 0x200c */
> -			if (intel_dp->active_mst_links > 0 &&
> -			    !drm_dp_channel_eq_ok(&esi[10], intel_dp-
> >lane_count)) {
> -				drm_dbg_kms(&i915->drm,
> -					    "channel EQ not ok,
> retraining\n");
> -				intel_dp_start_link_train(intel_dp);
> -				intel_dp_stop_link_train(intel_dp);
> -			}
> -
> -			drm_dbg_kms(&i915->drm, "got esi %3ph\n", esi);
> -			ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi,
> &handled);
> -
> -			if (handled) {
> -				for (retry = 0; retry < 3; retry++) {
> -					int wret;
> -					wret = drm_dp_dpcd_write(&intel_dp-
> >aux,
> -								 DP_SINK_COUNT
> _ESI+1,
> -								 &esi[1], 3);
> -					if (wret == 3) {
> -						break;
> -					}
> -				}
> -
> -				bret = intel_dp_get_sink_irq_esi(intel_dp,
> esi);
> -				if (bret == true) {
> -					drm_dbg_kms(&i915->drm,
> -						    "got esi2 %3ph\n", esi);
> -					goto go_again;
> -				}
> -			} else
> -				ret = 0;
> -
> -			return ret;
> -		} else {
> +		if (!bret) {
>  			drm_dbg_kms(&i915->drm,
>  				    "failed to get ESI - device may have
> failed\n");
> -			intel_dp->is_mst = false;
> -			drm_dp_mst_topology_mgr_set_mst(&intel_dp->mst_mgr,
> -							intel_dp->is_mst);
> +			return -EINVAL;
> +		}
> +
> +		/* check link status - esi[10] = 0x200c */
> +		/*
> +		 * FIXME kill this and use the SST retraining approach
> +		 * for MST as well.
> +		 */
> +		if (intel_dp->active_mst_links > 0 &&
> +		    !drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
> +			drm_dbg_kms(&i915->drm,
> +				    "channel EQ not ok, retraining\n");
> +			intel_dp_start_link_train(intel_dp);
> +			intel_dp_stop_link_train(intel_dp);
> +		}
> +
> +		drm_dbg_kms(&i915->drm, "got esi %3ph\n", esi);
> +
> +		drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, &handled);
> +		if (!handled)
> +			break;
> +
> +		for (retry = 0; retry < 3; retry++) {
> +			int wret;
> +
> +			wret = drm_dp_dpcd_write(&intel_dp->aux,
> +						 DP_SINK_COUNT_ESI+1,
> +						 &esi[1], 3);
> +			if (wret == 3)
> +				break;
>  		}
>  	}
> -	return -EINVAL;
> +
> +	return 0;
>  }
>  
>  static bool
> -- 
> 2.24.1
> 
-- 
Cheers,
	Lyude Paul (she/her)
	Associate Software Engineer at Red Hat