Re: [PATCH v2] drm/i915/dp: revert back to max link rate and lane count on eDP

[Jani Nikula <jani.nikula@intel.com>]

On Fri, 05 Apr 2019, Rodrigo Vivi <rodrigo.vivi@intel.com> wrote:
> On Fri, Apr 05, 2019 at 10:52:20AM +0300, Jani Nikula 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.
>> 
>> 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@linux.intel.com>
>> Cc: Manasi Navare <manasi.d.navare@intel.com>
>> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
>> Cc: Matt Atwood <matthew.s.atwood@intel.com>
>> Cc: "Lee, Shawn C" <shawn.c.lee@intel.com>
>> Cc: Dave Airlie <airlied@gmail.com>
>> Cc: intel-gfx@lists.freedesktop.org
>> Cc: <stable@vger.kernel.org> # v5.0+
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>
> I can hear from here your "I told you so"... Sorry!
>
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Thanks, pushed, please cherry-pick this for drm-intel-fixes.

BR,
Jani.



>
>> ---
>>  drivers/gpu/drm/i915/intel_dp.c | 69 +++++----------------------------
>>  1 file changed, 10 insertions(+), 59 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 72c490..dfa770 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;
>> @@ -2028,15 +1992,13 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
>>  	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;
>> @@ -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);
>> -- 
>> 2.20.1
>> 

-- 
Jani Nikula, Intel Open Source Graphics Center