> Subject: Re: [PATCH] drm/i915/dp: Add a meaningful return to > intel_dp_read_dsc_dpcd > > On Wed, 28 Jan 2026, Suraj Kandpal <[email protected]> wrote: > > Add a meaningful return to intel_dp_read_dsc_dpcd so tha we avoid > > unwanted DPCD reads which are not needed once we know DSC DPCD read > > fails. While we are at it remove the drm_err since we do not shout > > error during intel_dp_detect phase since it may take time to come up > > after pps_on is called for eDP scenario. > > Please pay more attention to the commit message.
Got it will fix it up > > > Signed-off-by: Suraj Kandpal <[email protected]> > > --- > > drivers/gpu/drm/i915/display/intel_dp.c | 24 +++++++++++++++--------- > > 1 file changed, 15 insertions(+), 9 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c > > b/drivers/gpu/drm/i915/display/intel_dp.c > > index 79fd3b8d8b25..d2ed8ec145a2 100644 > > --- a/drivers/gpu/drm/i915/display/intel_dp.c > > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > > @@ -4281,20 +4281,21 @@ static bool > intel_dp_get_colorimetry_status(struct intel_dp *intel_dp) > > return dprx & DP_VSC_SDP_EXT_FOR_COLORIMETRY_SUPPORTED; > > } > > > > -static void intel_dp_read_dsc_dpcd(struct drm_dp_aux *aux, > > - u8 > dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]) > > +static int intel_dp_read_dsc_dpcd(struct drm_dp_aux *aux, > > + u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE]) > > { > > if (drm_dp_dpcd_read(aux, DP_DSC_SUPPORT, dsc_dpcd, > > DP_DSC_RECEIVER_CAP_SIZE) < 0) { > > - drm_err(aux->drm_dev, > > - "Failed to read DPCD register 0x%x\n", > > - DP_DSC_SUPPORT); > > - return; > > + drm_dbg_kms(aux->drm_dev, > > + "Could not read DSC DPCD register 0x%x\n", > > + DP_DSC_SUPPORT); > > + return -EINVAL; > > If we want to do this properly, then let's propagate the actual error code > instead of inventing -EINVAL here. And switch to drm_dp_dpcd_read_data(), > which returns an error if not all bytes were transferred (also a case the > current implementation completely ignores). > > Finlly, the debug logging could log the error code. A combo of %pe in the > format string and ERR_PTR(ret) in the corresponding parameter will do it > nicely. Sure seems like good fix will get this done int the next revision. Regards, Suraj Kandpal > > > } > > > > drm_dbg_kms(aux->drm_dev, "DSC DPCD: %*ph\n", > > DP_DSC_RECEIVER_CAP_SIZE, > > dsc_dpcd); > > + return 0; > > } > > > > static void init_dsc_overall_throughput_limits(struct intel_connector > > *connector, bool is_branch) @@ -4345,8 +4346,11 @@ void > intel_dp_get_dsc_sink_cap(u8 dpcd_rev, > > if (dpcd_rev < DP_DPCD_REV_14) > > return; > > > > - intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, > > - connector->dp.dsc_dpcd); > > + if (intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, > > + connector->dp.dsc_dpcd) < 0) { > > + drm_err(display->drm, "Failed to read DSC DPCD register\n"); > > + return; > > + } > > > > if (drm_dp_dpcd_readb(connector->dp.dsc_decompression_aux, > DP_FEC_CAPABILITY, > > &connector->dp.fec_capability) < 0) { @@ -4376,7 > +4380,9 @@ > > static void intel_edp_get_dsc_sink_cap(u8 edp_dpcd_rev, struct > intel_connector * > > if (edp_dpcd_rev < DP_EDP_14) > > return; > > > > - intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, > connector->dp.dsc_dpcd); > > + if (intel_dp_read_dsc_dpcd(connector->dp.dsc_decompression_aux, > > + connector->dp.dsc_dpcd) < 0) > > + return; > > > > if (connector->dp.dsc_dpcd[0] & > DP_DSC_DECOMPRESSION_IS_SUPPORTED) > > init_dsc_overall_throughput_limits(connector, false); > > -- > Jani Nikula, Intel
