On Fri, 05 Apr 2019, Jani Nikula <jani.nikula@xxxxxxxxx> wrote:
> 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.
Fail, this one actually reverts back to wide-and-slow, while retaining
the use of optimal parameters rather than maxing them out.
It's a data point, but we'll want the full revert now.
BR,
Jani.
>
> 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@xxxxxxxxxxxxxxx>
> Cc: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> Cc: Matt Atwood <matthew.s.atwood@xxxxxxxxx>
> Cc: "Lee, Shawn C" <shawn.c.lee@xxxxxxxxx>
> Cc: Dave Airlie <airlied@xxxxxxxxx>
> Cc: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: <stable@xxxxxxxxxxxxxxx> # v5.0+
> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 67 +++++----------------------------
> 1 file changed, 9 insertions(+), 58 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 72c490..fd0f53 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1856,42 +1856,6 @@ intel_dp_compute_link_config_wide(struct intel_dp *intel_dp,
> return -EINVAL;
> }
>
> -/* Optimize link config in order: max bpp, min lanes, min clock */
> -static int
> -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 0;
> - }
> - }
> - }
> - }
> -
> - return -EINVAL;
> -}
> -
> static int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 dsc_max_bpc)
> {
> int i, num_bpc;
> @@ -2031,12 +1995,10 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
> if (intel_dp_is_edp(intel_dp) && intel_dp->edp_dpcd[0] < DP_EDP_14) {
> /*
> * 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;
> @@ -2050,22 +2012,11 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
> 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 */
> DRM_DEBUG_KMS("Force DSC en = %d\n", intel_dp->force_dsc_en);
--
Jani Nikula, Intel Open Source Graphics Center
