[PATCH 01/23] drm/i915/dp: Fix dsc bpp calculations, v2.
Maarten Lankhorst
maarten.lankhorst at linux.intel.com
Fri Sep 13 13:50:31 UTC 2019
There was a integer wraparound when mode_clock became too high,
and we didn't correct for the FEC overhead factor when dividing,
with the calculations breaking at HBR3.
As a result our calculated bpp was way too high, and the link width
limitation never came into effect.
Print out the resulting bpp calcululations as a sanity check, just
in case we ever have to debug it later on again.
We also used the wrong factor for FEC. While bspec mentions 2.4%,
all the calculations use 1/0.972261, and the same ratio should be
applied to data M/N as well, so use it there when FEC is enabled.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Fixes: d9218c8f6cf4 ("drm/i915/dp: Add helpers for Compressed BPP and Slice Count for DSC")
Cc: <stable at vger.kernel.org> # v5.0+
Cc: Manasi Navare <manasi.d.navare at intel.com>
---
drivers/gpu/drm/i915/display/intel_dp.c | 187 +++++++++++++-----------
drivers/gpu/drm/i915/display/intel_dp.h | 4 -
2 files changed, 99 insertions(+), 92 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index d09133a958e1..0a882a41ac6a 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -76,8 +76,8 @@
#define DP_DSC_MAX_ENC_THROUGHPUT_0 340000
#define DP_DSC_MAX_ENC_THROUGHPUT_1 400000
-/* DP DSC FEC Overhead factor = (100 - 2.4)/100 */
-#define DP_DSC_FEC_OVERHEAD_FACTOR 976
+/* DP DSC FEC Overhead factor = 1/(0.972261) */
+#define DP_DSC_FEC_OVERHEAD_FACTOR 972261
/* Compliance test status bits */
#define INTEL_DP_RESOLUTION_SHIFT_MASK 0
@@ -492,6 +492,96 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
return 0;
}
+static inline u32 mode_to_fec_clock(u32 mode_clock)
+{
+ return div_u64(mul_u32_u32(mode_clock, 1000000U),
+ DP_DSC_FEC_OVERHEAD_FACTOR);
+}
+
+static u16 intel_dp_dsc_get_output_bpp(u32 link_clock, u32 lane_count,
+ u32 mode_clock, u32 mode_hdisplay)
+{
+ u32 bits_per_pixel, max_bpp_small_joiner_ram;
+ int i;
+
+ /*
+ * Available Link Bandwidth(Kbits/sec) = (NumberOfLanes)*
+ * (LinkSymbolClock)* 8 * (TimeSlotsPerMTP)
+ * for SST -> TimeSlotsPerMTP is 1,
+ * for MST -> TimeSlotsPerMTP has to be calculated
+ */
+ bits_per_pixel = (link_clock * lane_count * 8) / mode_to_fec_clock(mode_clock);
+ DRM_DEBUG_KMS("Max link bpp: %u\n", bits_per_pixel);
+
+ /* Small Joiner Check: output bpp <= joiner RAM (bits) / Horiz. width */
+ max_bpp_small_joiner_ram = DP_DSC_MAX_SMALL_JOINER_RAM_BUFFER / mode_hdisplay;
+ DRM_DEBUG_KMS("Max small joiner bpp: %u\n", max_bpp_small_joiner_ram);
+
+ /*
+ * Greatest allowed DSC BPP = MIN (output BPP from available Link BW
+ * check, output bpp from small joiner RAM check)
+ */
+ bits_per_pixel = min(bits_per_pixel, max_bpp_small_joiner_ram);
+
+ /* Error out if the max bpp is less than smallest allowed valid bpp */
+ if (bits_per_pixel < valid_dsc_bpp[0]) {
+ DRM_DEBUG_KMS("Unsupported BPP %u, min %u\n",
+ bits_per_pixel, valid_dsc_bpp[0]);
+ return 0;
+ }
+
+ /* Find the nearest match in the array of known BPPs from VESA */
+ for (i = 0; i < ARRAY_SIZE(valid_dsc_bpp) - 1; i++) {
+ if (bits_per_pixel < valid_dsc_bpp[i + 1])
+ break;
+ }
+ bits_per_pixel = valid_dsc_bpp[i];
+
+ /*
+ * Compressed BPP in U6.4 format so multiply by 16, for Gen 11,
+ * fractional part is 0
+ */
+ return bits_per_pixel << 4;
+}
+
+static u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp,
+ int mode_clock, int mode_hdisplay)
+{
+ u8 min_slice_count, i;
+ int max_slice_width;
+
+ if (mode_clock <= DP_DSC_PEAK_PIXEL_RATE)
+ min_slice_count = DIV_ROUND_UP(mode_clock,
+ DP_DSC_MAX_ENC_THROUGHPUT_0);
+ else
+ min_slice_count = DIV_ROUND_UP(mode_clock,
+ DP_DSC_MAX_ENC_THROUGHPUT_1);
+
+ max_slice_width = drm_dp_dsc_sink_max_slice_width(intel_dp->dsc_dpcd);
+ if (max_slice_width < DP_DSC_MIN_SLICE_WIDTH_VALUE) {
+ DRM_DEBUG_KMS("Unsupported slice width %d by DP DSC Sink device\n",
+ max_slice_width);
+ return 0;
+ }
+ /* Also take into account max slice width */
+ min_slice_count = min_t(u8, min_slice_count,
+ DIV_ROUND_UP(mode_hdisplay,
+ max_slice_width));
+
+ /* Find the closest match to the valid slice count values */
+ for (i = 0; i < ARRAY_SIZE(valid_dsc_slicecount); i++) {
+ if (valid_dsc_slicecount[i] >
+ drm_dp_dsc_sink_max_slice_count(intel_dp->dsc_dpcd,
+ false))
+ break;
+ if (min_slice_count <= valid_dsc_slicecount[i])
+ return valid_dsc_slicecount[i];
+ }
+
+ DRM_DEBUG_KMS("Unsupported Slice Count %d\n", min_slice_count);
+ return 0;
+}
+
static enum drm_mode_status
intel_dp_mode_valid(struct drm_connector *connector,
struct drm_display_mode *mode)
@@ -2182,6 +2272,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
bool constant_n = drm_dp_has_quirk(&intel_dp->desc,
DP_DPCD_QUIRK_CONSTANT_N);
int ret = 0, output_bpp;
+ u32 data_clock;
if (HAS_PCH_SPLIT(dev_priv) && !HAS_DDI(dev_priv) && port != PORT_A)
pipe_config->has_pch_encoder = true;
@@ -2244,9 +2335,14 @@ intel_dp_compute_config(struct intel_encoder *encoder,
else
output_bpp = intel_dp_output_bpp(pipe_config, pipe_config->pipe_bpp);
+ if (pipe_config->fec_enable)
+ data_clock = mode_to_fec_clock(adjusted_mode->crtc_clock);
+ else
+ data_clock = adjusted_mode->crtc_clock;
+
intel_link_compute_m_n(output_bpp,
pipe_config->lane_count,
- adjusted_mode->crtc_clock,
+ data_clock,
pipe_config->port_clock,
&pipe_config->dp_m_n,
constant_n);
@@ -4363,91 +4459,6 @@ intel_dp_get_sink_irq_esi(struct intel_dp *intel_dp, u8 *sink_irq_vector)
DP_DPRX_ESI_LEN;
}
-u16 intel_dp_dsc_get_output_bpp(int link_clock, u8 lane_count,
- int mode_clock, int mode_hdisplay)
-{
- u16 bits_per_pixel, max_bpp_small_joiner_ram;
- int i;
-
- /*
- * Available Link Bandwidth(Kbits/sec) = (NumberOfLanes)*
- * (LinkSymbolClock)* 8 * ((100-FECOverhead)/100)*(TimeSlotsPerMTP)
- * FECOverhead = 2.4%, for SST -> TimeSlotsPerMTP is 1,
- * for MST -> TimeSlotsPerMTP has to be calculated
- */
- bits_per_pixel = (link_clock * lane_count * 8 *
- DP_DSC_FEC_OVERHEAD_FACTOR) /
- mode_clock;
-
- /* Small Joiner Check: output bpp <= joiner RAM (bits) / Horiz. width */
- max_bpp_small_joiner_ram = DP_DSC_MAX_SMALL_JOINER_RAM_BUFFER /
- mode_hdisplay;
-
- /*
- * Greatest allowed DSC BPP = MIN (output BPP from avaialble Link BW
- * check, output bpp from small joiner RAM check)
- */
- bits_per_pixel = min(bits_per_pixel, max_bpp_small_joiner_ram);
-
- /* Error out if the max bpp is less than smallest allowed valid bpp */
- if (bits_per_pixel < valid_dsc_bpp[0]) {
- DRM_DEBUG_KMS("Unsupported BPP %d\n", bits_per_pixel);
- return 0;
- }
-
- /* Find the nearest match in the array of known BPPs from VESA */
- for (i = 0; i < ARRAY_SIZE(valid_dsc_bpp) - 1; i++) {
- if (bits_per_pixel < valid_dsc_bpp[i + 1])
- break;
- }
- bits_per_pixel = valid_dsc_bpp[i];
-
- /*
- * Compressed BPP in U6.4 format so multiply by 16, for Gen 11,
- * fractional part is 0
- */
- return bits_per_pixel << 4;
-}
-
-u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp,
- int mode_clock,
- int mode_hdisplay)
-{
- u8 min_slice_count, i;
- int max_slice_width;
-
- if (mode_clock <= DP_DSC_PEAK_PIXEL_RATE)
- min_slice_count = DIV_ROUND_UP(mode_clock,
- DP_DSC_MAX_ENC_THROUGHPUT_0);
- else
- min_slice_count = DIV_ROUND_UP(mode_clock,
- DP_DSC_MAX_ENC_THROUGHPUT_1);
-
- max_slice_width = drm_dp_dsc_sink_max_slice_width(intel_dp->dsc_dpcd);
- if (max_slice_width < DP_DSC_MIN_SLICE_WIDTH_VALUE) {
- DRM_DEBUG_KMS("Unsupported slice width %d by DP DSC Sink device\n",
- max_slice_width);
- return 0;
- }
- /* Also take into account max slice width */
- min_slice_count = min_t(u8, min_slice_count,
- DIV_ROUND_UP(mode_hdisplay,
- max_slice_width));
-
- /* Find the closest match to the valid slice count values */
- for (i = 0; i < ARRAY_SIZE(valid_dsc_slicecount); i++) {
- if (valid_dsc_slicecount[i] >
- drm_dp_dsc_sink_max_slice_count(intel_dp->dsc_dpcd,
- false))
- break;
- if (min_slice_count <= valid_dsc_slicecount[i])
- return valid_dsc_slicecount[i];
- }
-
- DRM_DEBUG_KMS("Unsupported Slice Count %d\n", min_slice_count);
- return 0;
-}
-
static void
intel_pixel_encoding_setup_vsc(struct intel_dp *intel_dp,
const struct intel_crtc_state *crtc_state)
diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
index e01d1f89409d..14eb483dca27 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.h
+++ b/drivers/gpu/drm/i915/display/intel_dp.h
@@ -103,10 +103,6 @@ bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
bool intel_dp_source_supports_hbr3(struct intel_dp *intel_dp);
bool
intel_dp_get_link_status(struct intel_dp *intel_dp, u8 *link_status);
-u16 intel_dp_dsc_get_output_bpp(int link_clock, u8 lane_count,
- int mode_clock, int mode_hdisplay);
-u8 intel_dp_dsc_get_slice_count(struct intel_dp *intel_dp, int mode_clock,
- int mode_hdisplay);
bool intel_dp_read_dpcd(struct intel_dp *intel_dp);
bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp);
--
2.20.1
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