diff options
| author | Jani Nikula <jani.nikula@intel.com> | 2023-12-05 20:05:51 +0200 |
|---|---|---|
| committer | Jani Nikula <jani.nikula@intel.com> | 2023-12-11 13:15:35 +0200 |
| commit | e6861d8264cd43c5eb20196e53df36fd71ec5698 (patch) | |
| tree | 8e2b42784689cc9001cd9c4ecebaa8639c4f0930 /drivers | |
| parent | 324b70e997aab0a7deab8cb90711faccda4e98c8 (diff) | |
drm/i915/edp: don't write to DP_LINK_BW_SET when using rate select
The eDP 1.5 spec adds a clarification for eDP 1.4x:
> For eDP v1.4x, if the Source device chooses the Main-Link rate by way
> of DPCD 00100h, the Sink device shall ignore DPCD 00115h[2:0].
We write 0 to DP_LINK_BW_SET (DPCD 100h) even when using
DP_LINK_RATE_SET (DPCD 114h). Stop doing that, as it can cause the panel
to ignore the rate set method.
Moreover, 0 is a reserved value for DP_LINK_BW_SET, and should not be
used.
v2: Improve the comments (Ville)
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/9081
Tested-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231205180551.2476228-1-jani.nikula@intel.com
(cherry picked from commit 23b392b94acb0499f69706c5808c099f590ebcf4)
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/gpu/drm/i915/display/intel_dp_link_training.c | 31 |
1 files changed, 21 insertions, 10 deletions
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c index dbc1b66c8ee4..1abfafbbfa75 100644 --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c @@ -650,19 +650,30 @@ intel_dp_update_link_bw_set(struct intel_dp *intel_dp, const struct intel_crtc_state *crtc_state, u8 link_bw, u8 rate_select) { - u8 link_config[2]; + u8 lane_count = crtc_state->lane_count; - /* Write the link configuration data */ - link_config[0] = link_bw; - link_config[1] = crtc_state->lane_count; if (crtc_state->enhanced_framing) - link_config[1] |= DP_LANE_COUNT_ENHANCED_FRAME_EN; - drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, 2); + lane_count |= DP_LANE_COUNT_ENHANCED_FRAME_EN; + + if (link_bw) { + /* DP and eDP v1.3 and earlier link bw set method. */ + u8 link_config[] = { link_bw, lane_count }; - /* eDP 1.4 rate select method. */ - if (!link_bw) - drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_RATE_SET, - &rate_select, 1); + drm_dp_dpcd_write(&intel_dp->aux, DP_LINK_BW_SET, link_config, + ARRAY_SIZE(link_config)); + } else { + /* + * eDP v1.4 and later link rate set method. + * + * eDP v1.4x sinks shall ignore DP_LINK_RATE_SET if + * DP_LINK_BW_SET is set. Avoid writing DP_LINK_BW_SET. + * + * eDP v1.5 sinks allow choosing either, and the last choice + * shall be active. + */ + drm_dp_dpcd_writeb(&intel_dp->aux, DP_LANE_COUNT_SET, lane_count); + drm_dp_dpcd_writeb(&intel_dp->aux, DP_LINK_RATE_SET, rate_select); + } } /* |