The patch below does not apply to the 5.0-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5aae7832d1b4ec614996ea0f4fafc4d9855ec0b0 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Ville=20Syrj=C3=A4l=C3=A4?= ville.syrjala@linux.intel.com Date: Tue, 26 Mar 2019 16:49:02 +0200 Subject: [PATCH] drm/i915: Do not enable FEC without DSC MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

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

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 8891f29a8c7f..48da4a969a0a 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -1886,6 +1886,9 @@ static int intel_dp_dsc_compute_config(struct intel_dp *intel_dp, int pipe_bpp; int ret;

+ 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 -EINVAL;

@@ -2116,9 +2119,6 @@ intel_dp_compute_config(struct intel_encoder *encoder, if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK) return -EINVAL;

- pipe_config->fec_enable = !intel_dp_is_edp(intel_dp) && - intel_dp_supports_fec(intel_dp, pipe_config); - ret = intel_dp_compute_link_config(encoder, pipe_config, conn_state); if (ret < 0) return ret;