linux-kernel - [PATCH 5.0 003/101] drm/i915: Do not enable FEC without DSC

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Date:   Thu,  2 May 2019 17:20:05 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Anusha Srivatsa <anusha.srivatsa@...el.com>,
        Manasi Navare <manasi.d.navare@...el.com>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>
Subject: [PATCH 5.0 003/101] drm/i915: Do not enable FEC without DSC

From: Ville Syrjälä <ville.syrjala@...ux.intel.com>

commit 5aae7832d1b4ec614996ea0f4fafc4d9855ec0b0 upstream.

Currently we enable FEC even when DSC is no used. While that is
theoretically valid supposedly there isn't much of a benefit from
this. But more importantly we do not account for the FEC link
bandwidth overhead (2.4%) in the non-DSC link bandwidth computations.
So the code may think we have enough bandwidth when we in fact
do not.

Cc: stable@...r.kernel.org
Cc: Anusha Srivatsa <anusha.srivatsa@...el.com>
Cc: Manasi Navare <manasi.d.navare@...el.com>
Fixes: 240999cf339f ("i915/dp/fec: Add fec_enable to the crtc state.")
Signed-off-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190326144903.6617-1-ville.syrjala@linux.intel.com
Reviewed-by: Manasi Navare <manasi.d.navare@...el.com>
(cherry picked from commit 6fd3134ae3551d4802a04669c0f39f2f5c56f77d)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/i915/intel_dp.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -1871,6 +1871,9 @@ static bool intel_dp_dsc_compute_config(
 	u8 dsc_max_bpc;
 	int pipe_bpp;
 
+	pipe_config->fec_enable = !intel_dp_is_edp(intel_dp) &&
+		intel_dp_supports_fec(intel_dp, pipe_config);
+
 	if (!intel_dp_supports_dsc(intel_dp, pipe_config))
 		return false;
 
@@ -2097,9 +2100,6 @@ intel_dp_compute_config(struct intel_enc
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
 		return false;
 
-	pipe_config->fec_enable = !intel_dp_is_edp(intel_dp) &&
-				  intel_dp_supports_fec(intel_dp, pipe_config);
-
 	if (!intel_dp_compute_link_config(encoder, pipe_config, conn_state))
 		return false;