From 78776086371bf8aba4314a52a46c52d946984c61 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Ville=20Syrj=C3=A4l=C3=A4?= Date: Thu, 13 Apr 2023 19:49:13 +0300 Subject: [PATCH] drm/i915: Always enable CGM CSC on CHV MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit On CHV toggling the CGM CSC on/off while the pipe is running leads to underruns. Looks like we'd have to do the toggling strictly inside the start_of_vblank-frame_start window to avoid this, but that window is less than a scanline so there's no way we can guarantee hitting it. As a workaround let's just leave the CGM CSC permanently enabled. Fortunately the CGM gamma/degamma units don't seem to suffer from this malady. I also tried turning off CGM unit clock gating, but that did not help. Signed-off-by: Ville Syrjälä Link: https://patchwork.freedesktop.org/patch/msgid/20230413164916.4221-5-ville.syrjala@linux.intel.com Reviewed-by: Uma Shankar --- drivers/gpu/drm/i915/display/intel_color.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/display/intel_color.c b/drivers/gpu/drm/i915/display/intel_color.c index 7c14b2aba9e5..9581dc912d8e 100644 --- a/drivers/gpu/drm/i915/display/intel_color.c +++ b/drivers/gpu/drm/i915/display/intel_color.c @@ -605,6 +605,16 @@ static void chv_cgm_csc_convert_ctm(const struct intel_crtc_state *crtc_state, csc->coeff[i] = ctm_to_twos_complement(ctm->matrix[i], 4, 12); } +#define CHV_CGM_CSC_COEFF_1_0 (1 << 12) + +static const struct intel_csc_matrix chv_cgm_csc_matrix_identity = { + .coeff = { + CHV_CGM_CSC_COEFF_1_0, 0, 0, + 0, CHV_CGM_CSC_COEFF_1_0, 0, + 0, 0, CHV_CGM_CSC_COEFF_1_0, + }, +}; + static void chv_load_cgm_csc(struct intel_crtc *crtc, const struct intel_csc_matrix *csc) { @@ -667,9 +677,9 @@ static void chv_assign_csc(struct intel_crtc_state *crtc_state) chv_cgm_csc_convert_ctm(crtc_state, &crtc_state->csc); } else { - drm_WARN_ON(&i915->drm, (crtc_state->cgm_mode & CGM_PIPE_MODE_CSC) != 0); + drm_WARN_ON(&i915->drm, (crtc_state->cgm_mode & CGM_PIPE_MODE_CSC) == 0); - intel_csc_clear(&crtc_state->csc); + crtc_state->csc = chv_cgm_csc_matrix_identity; } } @@ -2033,6 +2043,13 @@ static u32 chv_cgm_mode(const struct intel_crtc_state *crtc_state) !lut_is_legacy(crtc_state->hw.gamma_lut)) cgm_mode |= CGM_PIPE_MODE_GAMMA; + /* + * Toggling the CGM CSC on/off outside of the tiny window + * between start of vblank and frame start causes underruns. + * Always enable the CGM CSC as a workaround. + */ + cgm_mode |= CGM_PIPE_MODE_CSC; + return cgm_mode; } -- 2.11.0