Use recommended values as per wa_14021694213 to compare with the calculated value and choose minimum of them.
v2: corrected checkpatch warning and retain the restriction for min_hblank (Jani) v3: use calculated value to compare with recomended value and choose minimum of them (Imre) v4: As driver supported min bpc is 8, omit the condition check for bpc6 with ycbcr420. Added a note for the same (Imre) v5: Add a warn for the unexpected case of 6bpc + uhbr + ycbcr420 Bspec: 74379 Signed-off-by: Arun R Murthy <[email protected]> --- Changes in v5: - EDITME: describe what is new in this series revision. - EDITME: use bulletpoints and terse descriptions. - Link to v4: https://lore.kernel.org/r/[email protected] --- drivers/gpu/drm/i915/display/intel_dp.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c index 54d88f24b6893e1f8009f00dda87d8dae5dfc137..1cc19f3e7729c25d2066f42601a18bdfa03b2721 100644 --- a/drivers/gpu/drm/i915/display/intel_dp.c +++ b/drivers/gpu/drm/i915/display/intel_dp.c @@ -3182,7 +3182,26 @@ int intel_dp_compute_min_hblank(struct intel_crtc_state *crtc_state, */ min_hblank = min_hblank - 2; - min_hblank = min(10, min_hblank); + /* + * min_hblank formula is undergoing a change, to avoid underrun use the + * recomended value in spec to compare with the calculated one and use the + * minimum value + */ + if (intel_dp_is_uhbr(crtc_state)) { + /* + * Note: Driver doesn't support compressed bpp 6. + * Its unusual to have 6bpc with YCBCR420, for which the spec suggests + * a minimum hblank value of 2(Hence this condition is omitted). + */ + drm_WARN(display->drm, (crtc_state->dsc.compression_enable && + crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420 && + crtc_state->dsc.compressed_bpp_x16 == 6), + "Unusual to have compressed bpp 6 with ycbcr420\n"); + min_hblank = min(3, min_hblank); + } else { + min_hblank = min(10, min_hblank); + } + crtc_state->min_hblank = min_hblank; return 0; --- base-commit: eb0c2b25072b5c56e8c41d7099050bf53bebaa14 change-id: 20250728-min_hblank-263ceb40508c Best regards, -- Arun R Murthy <[email protected]>
