[PATCH v7 1/6] drm/dp_mst: Add PBN calculation for DSC modes

[PATCH v7 1/6] drm/dp_mst: Add PBN calculation for DSC modes

[David Francis]

With DSC, bpp can be fractional in multiples of 1/16.

Change drm_dp_calc_pbn_mode to reflect this, adding a new
parameter bool dsc. When this parameter is true, treat the
bpp parameter as having units not of bits per pixel, but
1/16 of a bit per pixel

v2: Don't add separate function for this

Cc: amd-gfx@lists.freedesktop.org
Cc: nouveau@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: David Francis <David.Francis@amd.com>
---
 .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c    |  2 +-
 drivers/gpu/drm/drm_dp_mst_topology.c            | 16 ++++++++++++----
 drivers/gpu/drm/i915/display/intel_dp_mst.c      |  2 +-
 drivers/gpu/drm/nouveau/dispnv50/disp.c          |  2 +-
 drivers/gpu/drm/radeon/radeon_dp_mst.c           |  2 +-
 include/drm/drm_dp_mst_helper.h                  |  3 +--
 6 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
index a0ed0154a9f0..abafb5221b44 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
@@ -235,7 +235,7 @@ bool dm_helpers_dp_mst_write_payload_allocation_table(
 
 		/* TODO need to know link rate */
 
-		pbn = drm_dp_calc_pbn_mode(clock, bpp);
+		pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
 
 		slots = drm_dp_find_vcpi_slots(mst_mgr, pbn);
 		ret = drm_dp_mst_allocate_vcpi(mst_mgr, mst_port, pbn, slots);
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 82add736e17d..3e7b7553cf4d 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3534,10 +3534,11 @@ EXPORT_SYMBOL(drm_dp_check_act_status);
  * drm_dp_calc_pbn_mode() - Calculate the PBN for a mode.
  * @clock: dot clock for the mode
  * @bpp: bpp for the mode.
+ * @dsc: DSC mode. If true, bpp has units of 1/16 of a bit per pixel
  *
  * This uses the formula in the spec to calculate the PBN value for a mode.
  */
-int drm_dp_calc_pbn_mode(int clock, int bpp)
+int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc)
 {
 	u64 kbps;
 	s64 peak_kbps;
@@ -3555,11 +3556,18 @@ int drm_dp_calc_pbn_mode(int clock, int bpp)
 	 * peak_kbps *= (1006/1000)
 	 * peak_kbps *= (64/54)
 	 * peak_kbps *= 8    convert to bytes
+	 *
+	 * If the bpp is in units of 1/16, further divide by 16. Put this
+	 * factor in the numerator rather than the denominator to avoid
+	 * integer overflow
 	 */
 
 	numerator = 64 * 1006;
 	denominator = 54 * 8 * 1000 * 1000;
 
+	if (dsc)
+		numerator /= 16;
+
 	kbps *= numerator;
 	peak_kbps = drm_fixp_from_fraction(kbps, denominator);
 
@@ -3570,19 +3578,19 @@ EXPORT_SYMBOL(drm_dp_calc_pbn_mode);
 static int test_calc_pbn_mode(void)
 {
 	int ret;
-	ret = drm_dp_calc_pbn_mode(154000, 30);
+	ret = drm_dp_calc_pbn_mode(154000, 30, false);
 	if (ret != 689) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				154000, 30, 689, ret);
 		return -EINVAL;
 	}
-	ret = drm_dp_calc_pbn_mode(234000, 30);
+	ret = drm_dp_calc_pbn_mode(234000, 30, false);
 	if (ret != 1047) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				234000, 30, 1047, ret);
 		return -EINVAL;
 	}
-	ret = drm_dp_calc_pbn_mode(297000, 24);
+	ret = drm_dp_calc_pbn_mode(297000, 24, false);
 	if (ret != 1063) {
 		DRM_ERROR("PBN calculation test failed - clock %d, bpp %d, expected PBN %d, actual PBN %d.\n",
 				297000, 24, 1063, ret);
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 2c5ac3dd647f..4f17f61f4453 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -61,7 +61,7 @@ static int intel_dp_mst_compute_link_config(struct intel_encoder *encoder,
 		crtc_state->pipe_bpp = bpp;
 
 		crtc_state->pbn = drm_dp_calc_pbn_mode(adjusted_mode->crtc_clock,
-						       crtc_state->pipe_bpp);
+						       crtc_state->pipe_bpp, false);
 
 		slots = drm_dp_atomic_find_vcpi_slots(state, &intel_dp->mst_mgr,
 						      port, crtc_state->pbn);
diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 5c36c75232e6..c68783c1f3fa 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -782,7 +782,7 @@ nv50_msto_atomic_check(struct drm_encoder *encoder,
 			const int bpp = connector->display_info.bpc * 3;
 			const int clock = crtc_state->adjusted_mode.clock;
 
-			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp);
+			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp, false);
 		}
 
 		slots = drm_dp_atomic_find_vcpi_slots(state, &mstm->mgr,
diff --git a/drivers/gpu/drm/radeon/radeon_dp_mst.c b/drivers/gpu/drm/radeon/radeon_dp_mst.c
index 2994f07fbad9..c997f88218f2 100644
--- a/drivers/gpu/drm/radeon/radeon_dp_mst.c
+++ b/drivers/gpu/drm/radeon/radeon_dp_mst.c
@@ -514,7 +514,7 @@ static bool radeon_mst_mode_fixup(struct drm_encoder *encoder,
 
 	mst_enc = radeon_encoder->enc_priv;
 
-	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp);
+	mst_enc->pbn = drm_dp_calc_pbn_mode(adjusted_mode->clock, bpp, false);
 
 	mst_enc->primary->active_device = mst_enc->primary->devices & mst_enc->connector->devices;
 	DRM_DEBUG_KMS("setting active device to %08x from %08x %08x for encoder %d\n",
diff --git a/include/drm/drm_dp_mst_helper.h b/include/drm/drm_dp_mst_helper.h
index 2ba6253ea6d3..9116b2c95239 100644
--- a/include/drm/drm_dp_mst_helper.h
+++ b/include/drm/drm_dp_mst_helper.h
@@ -610,8 +610,7 @@ bool drm_dp_mst_port_has_audio(struct drm_dp_mst_topology_mgr *mgr,
 struct edid *drm_dp_mst_get_edid(struct drm_connector *connector, struct drm_dp_mst_topology_mgr *mgr, struct drm_dp_mst_port *port);
 
 
-int drm_dp_calc_pbn_mode(int clock, int bpp);
-
+int drm_dp_calc_pbn_mode(int clock, int bpp, bool dsc);
 
 bool drm_dp_mst_allocate_vcpi(struct drm_dp_mst_topology_mgr *mgr,
 			      struct drm_dp_mst_port *port, int pbn, int slots);
-- 
2.17.1

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