[Intel-gfx] [PATCH 13/16] drm/i915/dsc/mtl: Add support for fractional bpp

[Ankit Nautiyal]

From: Vandita Kulkarni <vandita.kulkarni at intel.com>

Consider the fractional bpp while reading the qp values.

Signed-off-by: Vandita Kulkarni <vandita.kulkarni at intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_qp_tables.c |  3 ---
 drivers/gpu/drm/i915/display/intel_vdsc.c      | 12 +++++++++---
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_qp_tables.c b/drivers/gpu/drm/i915/display/intel_qp_tables.c
index 6f8e4ec5c0fb..a0094287dc81 100644
--- a/drivers/gpu/drm/i915/display/intel_qp_tables.c
+++ b/drivers/gpu/drm/i915/display/intel_qp_tables.c
@@ -21,9 +21,6 @@
  * These qp tables are as per the C model
  * and it has the rows pointing to bpps which increment
  * in steps of 0.5
- * We do not support fractional bpps as of today,
- * hence we would skip the fractional bpps during
- * our references for qp calclulations.
  */
 static const u8 rc_range_minqp444_8bpc[DSC_NUM_BUF_RANGES][RC_RANGE_QP444_8BPC_MAX_NUM_BPP] = {
 	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c b/drivers/gpu/drm/i915/display/intel_vdsc.c
index ed5c85229414..3e39f682b19f 100644
--- a/drivers/gpu/drm/i915/display/intel_vdsc.c
+++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
@@ -378,6 +378,7 @@ calculate_rc_params(struct rc_parameters *rc,
 {
 	int bpc = vdsc_cfg->bits_per_component;
 	int bpp = vdsc_cfg->bits_per_pixel >> 4;
+	int fractional_bits = vdsc_cfg->bits_per_pixel & 0xf;
 	static const s8 ofs_und6[] = {
 		0, -2, -2, -4, -6, -6, -8, -8, -8, -10, -10, -12, -12, -12, -12
 	};
@@ -418,7 +419,13 @@ calculate_rc_params(struct rc_parameters *rc,
 	rc->rc_quant_incr_limit0 = 11 + qp_bpc_modifier;
 	rc->rc_quant_incr_limit1 = 11 + qp_bpc_modifier;
 
-	bpp_i  = (2 * (bpp - 6));
+	/*
+	 * QP table rows have values in increment of 0.5.
+	 * So 6.0 bpp to 6.4375 will have index 0, 6.5 to 6.9375 will have index 1,
+	 * and so on.
+	 * 0.5 represented as 0x8 in U6.4 format.
+	 */
+	bpp_i  = ((bpp - 6) + (fractional_bits < 0x8 ? 0 : 1));
 	for (buf_i = 0; buf_i < DSC_NUM_BUF_RANGES; buf_i++) {
 		/* Read range_minqp and range_max_qp from qp tables */
 		rc->rc_range_params[buf_i].range_min_qp =
@@ -466,8 +473,7 @@ int intel_dsc_compute_params(struct intel_crtc_state *pipe_config)
 	/* Gen 11 does not support VBR */
 	vdsc_cfg->vbr_enable = false;
 
-	/* Gen 11 only supports integral values of bpp */
-	vdsc_cfg->bits_per_pixel = compressed_bpp << 4;
+	vdsc_cfg->bits_per_pixel = pipe_config->dsc.compressed_bpp;
 	vdsc_cfg->bits_per_component = pipe_config->pipe_bpp / 3;
 
 	for (i = 0; i < DSC_NUM_BUF_RANGES - 1; i++) {
-- 
2.25.1