[Intel-gfx] [PATCH 5.0 084/117] drm/i915/dp: revert back to max link rate and lane count on eDP

[Greg Kroah-Hartman]

From: Jani Nikula <jani.nikula at intel.com>

commit 21635d7311734d2d1b177f8a95e2f9386174b76d upstream.

Commit 7769db588384 ("drm/i915/dp: optimize eDP 1.4+ link config fast
and narrow") started to optize the eDP 1.4+ link config, both per spec
and as preparation for display stream compression support.

Sadly, we again face panels that flat out fail with parameters they
claim to support. Revert, and go back to the drawing board.

v2: Actually revert to max params instead of just wide-and-slow.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109959
Fixes: 7769db588384 ("drm/i915/dp: optimize eDP 1.4+ link config fast and narrow")
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Manasi Navare <manasi.d.navare at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Matt Atwood <matthew.s.atwood at intel.com>
Cc: "Lee, Shawn C" <shawn.c.lee at intel.com>
Cc: Dave Airlie <airlied at gmail.com>
Cc: intel-gfx at lists.freedesktop.org
Cc: <stable at vger.kernel.org> # v5.0+
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Reviewed-by: Manasi Navare <manasi.d.navare at intel.com>
Tested-by: Albert Astals Cid <aacid at kde.org> # v5.0 backport
Tested-by: Emanuele Panigati <ilpanich at gmail.com> # v5.0 backport
Tested-by: Matteo Iervasi <matteoiervasi at gmail.com> # v5.0 backport
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190405075220.9815-1-jani.nikula@intel.com
(cherry picked from commit f11cb1c19ad0563b3c1ea5eb16a6bac0e401f428)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>


---
 drivers/gpu/drm/i915/intel_dp.c |   69 +++++-----------------------------------
 1 file changed, 10 insertions(+), 59 deletions(-)

--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1845,42 +1845,6 @@ intel_dp_compute_link_config_wide(struct
 	return false;
 }
 
-/* Optimize link config in order: max bpp, min lanes, min clock */
-static bool
-intel_dp_compute_link_config_fast(struct intel_dp *intel_dp,
-				  struct intel_crtc_state *pipe_config,
-				  const struct link_config_limits *limits)
-{
-	struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
-	int bpp, clock, lane_count;
-	int mode_rate, link_clock, link_avail;
-
-	for (bpp = limits->max_bpp; bpp >= limits->min_bpp; bpp -= 2 * 3) {
-		mode_rate = intel_dp_link_required(adjusted_mode->crtc_clock,
-						   bpp);
-
-		for (lane_count = limits->min_lane_count;
-		     lane_count <= limits->max_lane_count;
-		     lane_count <<= 1) {
-			for (clock = limits->min_clock; clock <= limits->max_clock; clock++) {
-				link_clock = intel_dp->common_rates[clock];
-				link_avail = intel_dp_max_data_rate(link_clock,
-								    lane_count);
-
-				if (mode_rate <= link_avail) {
-					pipe_config->lane_count = lane_count;
-					pipe_config->pipe_bpp = bpp;
-					pipe_config->port_clock = link_clock;
-
-					return true;
-				}
-			}
-		}
-	}
-
-	return false;
-}
-
 static int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 dsc_max_bpc)
 {
 	int i, num_bpc;
@@ -2013,15 +1977,13 @@ intel_dp_compute_link_config(struct inte
 	limits.min_bpp = 6 * 3;
 	limits.max_bpp = intel_dp_compute_bpp(intel_dp, pipe_config);
 
-	if (intel_dp_is_edp(intel_dp) && intel_dp->edp_dpcd[0] < DP_EDP_14) {
+	if (intel_dp_is_edp(intel_dp)) {
 		/*
 		 * Use the maximum clock and number of lanes the eDP panel
-		 * advertizes being capable of. The eDP 1.3 and earlier panels
-		 * are generally designed to support only a single clock and
-		 * lane configuration, and typically these values correspond to
-		 * the native resolution of the panel. With eDP 1.4 rate select
-		 * and DSC, this is decreasingly the case, and we need to be
-		 * able to select less than maximum link config.
+		 * advertizes being capable of. The panels are generally
+		 * designed to support only a single clock and lane
+		 * configuration, and typically these values correspond to the
+		 * native resolution of the panel.
 		 */
 		limits.min_lane_count = limits.max_lane_count;
 		limits.min_clock = limits.max_clock;
@@ -2035,22 +1997,11 @@ intel_dp_compute_link_config(struct inte
 		      intel_dp->common_rates[limits.max_clock],
 		      limits.max_bpp, adjusted_mode->crtc_clock);
 
-	if (intel_dp_is_edp(intel_dp))
-		/*
-		 * Optimize for fast and narrow. eDP 1.3 section 3.3 and eDP 1.4
-		 * section A.1: "It is recommended that the minimum number of
-		 * lanes be used, using the minimum link rate allowed for that
-		 * lane configuration."
-		 *
-		 * Note that we use the max clock and lane count for eDP 1.3 and
-		 * earlier, and fast vs. wide is irrelevant.
-		 */
-		ret = intel_dp_compute_link_config_fast(intel_dp, pipe_config,
-							&limits);
-	else
-		/* Optimize for slow and wide. */
-		ret = intel_dp_compute_link_config_wide(intel_dp, pipe_config,
-							&limits);
+	/*
+	 * Optimize for slow and wide. This is the place to add alternative
+	 * optimization policy.
+	 */
+	ret = intel_dp_compute_link_config_wide(intel_dp, pipe_config, &limits);
 
 	/* enable compression if the mode doesn't fit available BW */
 	if (!ret) {