drm/i915/dp: Fix dsc bpp calculations, v5.
authorMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Wed, 25 Sep 2019 08:21:09 +0000 (10:21 +0200)
committerRodrigo Vivi <rodrigo.vivi@intel.com>
Thu, 3 Oct 2019 05:20:22 +0000 (22:20 -0700)
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.

This fixes the FIFO underrun we are seeing with FEC enabled.

Changes since v2:
- Handle fec_enable in intel_link_compute_m_n, so only data M/N is adjusted. (Ville)
- Fix initial hardware readout for FEC. (Ville)
Changes since v3:
- Remove bogus fec_to_mode_clock. (Ville)
Changes since v4:
- Use the correct register for icl. (Ville)
- Split hw readout to a separate patch.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Fixes: d9218c8f6cf4 ("drm/i915/dp: Add helpers for Compressed BPP and Slice Count for DSC")
Cc: <stable@vger.kernel.org> # v5.0+
Cc: Manasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190925082110.17439-1-maarten.lankhorst@linux.intel.com
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
(cherry picked from commit ed06efb801bd291e935238d3fba46fa03d098f0e)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
drivers/gpu/drm/i915/display/intel_display.c
drivers/gpu/drm/i915/display/intel_display.h
drivers/gpu/drm/i915/display/intel_dp.c
drivers/gpu/drm/i915/display/intel_dp.h
drivers/gpu/drm/i915/display/intel_dp_mst.c

index b51d1ce..ce05e80 100644 (file)
@@ -7261,7 +7261,7 @@ retry:
        pipe_config->fdi_lanes = lane;
 
        intel_link_compute_m_n(pipe_config->pipe_bpp, lane, fdi_dotclock,
-                              link_bw, &pipe_config->fdi_m_n, false);
+                              link_bw, &pipe_config->fdi_m_n, false, false);
 
        ret = ironlake_check_fdi_lanes(dev, intel_crtc->pipe, pipe_config);
        if (ret == -EDEADLK)
@@ -7508,11 +7508,15 @@ void
 intel_link_compute_m_n(u16 bits_per_pixel, int nlanes,
                       int pixel_clock, int link_clock,
                       struct intel_link_m_n *m_n,
-                      bool constant_n)
+                      bool constant_n, bool fec_enable)
 {
-       m_n->tu = 64;
+       u32 data_clock = bits_per_pixel * pixel_clock;
+
+       if (fec_enable)
+               data_clock = intel_dp_mode_to_fec_clock(data_clock);
 
-       compute_m_n(bits_per_pixel * pixel_clock,
+       m_n->tu = 64;
+       compute_m_n(data_clock,
                    link_clock * nlanes * 8,
                    &m_n->gmch_m, &m_n->gmch_n,
                    constant_n);
index e57e696..01fa87a 100644 (file)
@@ -414,7 +414,7 @@ enum phy_fia {
 void intel_link_compute_m_n(u16 bpp, int nlanes,
                            int pixel_clock, int link_clock,
                            struct intel_link_m_n *m_n,
-                           bool constant_n);
+                           bool constant_n, bool fec_enable);
 bool is_ccs_modifier(u64 modifier);
 void lpt_disable_clkout_dp(struct drm_i915_private *dev_priv);
 u32 intel_plane_fb_max_stride(struct drm_i915_private *dev_priv,
index 921ad0a..57e9f0b 100644 (file)
@@ -78,8 +78,8 @@
 #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
@@ -494,6 +494,97 @@ int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
        return 0;
 }
 
+u32 intel_dp_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) /
+                        intel_dp_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)
@@ -2226,7 +2317,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
                               adjusted_mode->crtc_clock,
                               pipe_config->port_clock,
                               &pipe_config->dp_m_n,
-                              constant_n);
+                              constant_n, pipe_config->fec_enable);
 
        if (intel_connector->panel.downclock_mode != NULL &&
                dev_priv->drrs.type == SEAMLESS_DRRS_SUPPORT) {
@@ -2236,7 +2327,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
                                               intel_connector->panel.downclock_mode->clock,
                                               pipe_config->port_clock,
                                               &pipe_config->dp_m2_n2,
-                                              constant_n);
+                                              constant_n, pipe_config->fec_enable);
        }
 
        if (!HAS_DDI(dev_priv))
@@ -4323,91 +4414,6 @@ 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)
index 657bbb1..00981fb 100644 (file)
@@ -102,10 +102,6 @@ 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);
@@ -118,4 +114,6 @@ static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
        return ~((1 << lane_count) - 1) & 0xf;
 }
 
+u32 intel_dp_mode_to_fec_clock(u32 mode_clock);
+
 #endif /* __INTEL_DP_H__ */
index 6df240a..b6e3504 100644 (file)
@@ -81,7 +81,7 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
                               adjusted_mode->crtc_clock,
                               crtc_state->port_clock,
                               &crtc_state->dp_m_n,
-                              constant_n);
+                              constant_n, crtc_state->fec_enable);
        crtc_state->dp_m_n.tu = slots;
 
        return 0;