drm/amd/display: fixed an error related to 4:2:0/4:2:2 DSC

[Why]
OPTC_BYTES_PER_PIXEL calculation for 4:2:2 and 4:2:0 could have error.

[How]
Change to use following formula:
OPTC_DSC_BYTES_PER_PIXEL = ceiling((chunk size * 2^28) / slice width)

v2: squash in 64 bit divide fix (Alex)
Reviewed-by: Wenjing Liu <Wenjing.Liu@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Bing Guo <Bing.Guo@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/dsc/rc_calc_fpu.c

@@ -61,16 +61,6 @@ static double dsc_roundf(double num)
 	return (int)(num);
 }
 
-static double dsc_ceil(double num)
-{
-	double retval = (int)num;
-
-	if (retval != num && num > 0)
-		retval = num + 1;
-
-	return (int)retval;
-}
-
 static void get_qp_set(qp_set qps, enum colour_mode cm, enum bits_per_comp bpc,
 		       enum max_min max_min, float bpp)
 {
@@ -268,24 +258,3 @@ void _do_calc_rc_params(struct rc_params *rc,
 	rc->rc_buf_thresh[13] = 8064;
 }
 
-u32 _do_bytes_per_pixel_calc(int slice_width,
-		u16 drm_bpp,
-		bool is_navite_422_or_420)
-{
-	float bpp;
-	u32 bytes_per_pixel;
-	double d_bytes_per_pixel;
-
-	dc_assert_fp_enabled();
-
-	bpp = ((float)drm_bpp / 16.0);
-	d_bytes_per_pixel = dsc_ceil(bpp * slice_width / 8.0) / slice_width;
-	// TODO: Make sure the formula for calculating this is precise (ceiling
-	// vs. floor, and at what point they should be applied)
-	if (is_navite_422_or_420)
-		d_bytes_per_pixel /= 2;
-
-	bytes_per_pixel = (u32)dsc_ceil(d_bytes_per_pixel * 0x10000000);
-
-	return bytes_per_pixel;
-}

drivers/gpu/drm/amd/display/dc/dml/dsc/rc_calc_fpu.h

@@ -78,10 +78,6 @@ struct qp_entry {
 
 typedef struct qp_entry qp_table[];
 
-u32 _do_bytes_per_pixel_calc(int slice_width,
-		u16 drm_bpp,
-		bool is_navite_422_or_420);
-
 void _do_calc_rc_params(struct rc_params *rc,
 		enum colour_mode cm,
 		enum bits_per_comp bpc,

drivers/gpu/drm/amd/display/dc/dsc/rc_calc.c

@@ -60,31 +60,3 @@ void calc_rc_params(struct rc_params *rc, const struct drm_dsc_config *pps)
 			   pps->dsc_version_minor);
 	DC_FP_END();
 }
-
-/**
- * calc_dsc_bytes_per_pixel - calculate bytes per pixel
- * @pps: DRM struct with all required DSC values
- *
- * Based on the information inside drm_dsc_config, this function calculates the
- * total of bytes per pixel.
- *
- * @note This calculation requires float point operation, most of it executes
- * under kernel_fpu_{begin,end}.
- *
- * Return:
- * Return the number of bytes per pixel
- */
-u32 calc_dsc_bytes_per_pixel(const struct drm_dsc_config *pps)
-
-{
-	u32 ret;
-	u16 drm_bpp = pps->bits_per_pixel;
-	int slice_width  = pps->slice_width;
-	bool is_navite_422_or_420 = pps->native_422 || pps->native_420;
-
-	DC_FP_START();
-	ret = _do_bytes_per_pixel_calc(slice_width, drm_bpp,
-				       is_navite_422_or_420);
-	DC_FP_END();
-	return ret;
-}

drivers/gpu/drm/amd/display/dc/dsc/rc_calc.h

@@ -30,7 +30,6 @@
 #include "dml/dsc/rc_calc_fpu.h"
 
 void calc_rc_params(struct rc_params *rc, const struct drm_dsc_config *pps);
-u32 calc_dsc_bytes_per_pixel(const struct drm_dsc_config *pps);
 
 #endif
 

drivers/gpu/drm/amd/display/dc/dsc/rc_calc_dpi.c

@@ -100,8 +100,7 @@ int dscc_compute_dsc_parameters(const struct drm_dsc_config *pps, struct dsc_par
 	int              ret;
 	struct rc_params rc;
 	struct drm_dsc_config   dsc_cfg;
-
-	dsc_params->bytes_per_pixel = calc_dsc_bytes_per_pixel(pps);
+	unsigned long long tmp;
 
 	calc_rc_params(&rc, pps);
 	dsc_params->pps = *pps;
@@ -113,6 +112,9 @@ int dscc_compute_dsc_parameters(const struct drm_dsc_config *pps, struct dsc_par
 	dsc_cfg.mux_word_size = dsc_params->pps.bits_per_component <= 10 ? 48 : 64;
 
 	ret = drm_dsc_compute_rc_parameters(&dsc_cfg);
+	tmp = (unsigned long long)dsc_cfg.slice_chunk_size * 0x10000000 + (dsc_cfg.slice_width - 1);
+	do_div(tmp, (uint32_t)dsc_cfg.slice_width);  //ROUND-UP
+	dsc_params->bytes_per_pixel = (uint32_t)tmp;
 
 	copy_pps_fields(&dsc_params->pps, &dsc_cfg);
 	dsc_params->rc_buffer_model_size = dsc_cfg.rc_bits;