drm/amd/display: Include scaling factor for SubVP command

[Description]
For SubVP scaling cases, we must include the scaling
info as part of the cmd. This is required when converting
OTG line to HUBP line for the MALL_START_LINE programming.

Reviewed-by: Jun Lei <[e-mail]>
Acked-by: Brian Chang <[e-mail]>
Signed-off-by: Alvin Lee <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/basics/conversion.c

···
 		matrix[i] = (uint16_t)reg_value;
 	}
 }
+
+static uint32_t find_gcd(uint32_t a, uint32_t b)
+{
+	uint32_t remainder = 0;
+	while (b != 0) {
+		remainder = a % b;
+		a = b;
+		b = remainder;
+	}
+	return a;
+}
+
+void reduce_fraction(uint32_t num, uint32_t den,
+		uint32_t *out_num, uint32_t *out_den)
+{
+	uint32_t gcd = 0;
+
+	gcd = find_gcd(num, den);
+	*out_num = num / gcd;
+	*out_den = den / gcd;
+}

drivers/gpu/drm/amd/display/dc/basics/conversion.h

···
 	struct fixed31_32 *flt,
 	uint32_t buffer_size);
 
+void reduce_fraction(uint32_t num, uint32_t den,
+		uint32_t *out_num, uint32_t *out_den);
+
 static inline unsigned int log_2(unsigned int num)
 {
 	return ilog2(num);

drivers/gpu/drm/amd/display/dc/dc_dmub_srv.c

···
 #include "dm_helpers.h"
 #include "dc_hw_types.h"
 #include "core_types.h"
+#include "../basics/conversion.h"
 
 #define CTX dc_dmub_srv->ctx
 #define DC_LOGGER CTX->logger
···
 			&cmd->fw_assisted_mclk_switch_v2.config_data.pipe_data[cmd_pipe_index];
 	struct dc_crtc_timing *main_timing = &subvp_pipe->stream->timing;
 	struct dc_crtc_timing *phantom_timing = &subvp_pipe->stream->mall_stream_config.paired_stream->timing;
+	uint32_t out_num, out_den;
 
 	pipe_data->mode = SUBVP;
 	pipe_data->pipe_config.subvp_data.pix_clk_100hz = subvp_pipe->stream->timing.pix_clk_100hz;
···
 	pipe_data->pipe_config.subvp_data.mall_region_lines = phantom_timing->v_addressable;
 	pipe_data->pipe_config.subvp_data.main_pipe_index = subvp_pipe->pipe_idx;
 	pipe_data->pipe_config.subvp_data.is_drr = subvp_pipe->stream->ignore_msa_timing_param;
+
+	/* Calculate the scaling factor from the src and dst height.
+	 * e.g. If 3840x2160 being downscaled to 1920x1080, the scaling factor is 1/2.
+	 * Reduce the fraction 1080/2160 = 1/2 for the "scaling factor"
+	 */
+	reduce_fraction(subvp_pipe->stream->src.height, subvp_pipe->stream->dst.height, &out_num, &out_den);
+	// TODO: Uncomment below lines once DMCUB include headers are promoted
+	//pipe_data->pipe_config.subvp_data.scale_factor_numerator = out_num;
+	//pipe_data->pipe_config.subvp_data.scale_factor_denominator = out_den;
 
 	// Prefetch lines is equal to VACTIVE + BP + VSYNC
 	pipe_data->pipe_config.subvp_data.prefetch_lines =

drivers/gpu/drm/amd/display/dc/dcn321/dcn321_resource.c

···
 	dc->caps.subvp_prefetch_end_to_mall_start_us = 15;
 	dc->caps.subvp_swath_height_margin_lines = 16;
 	dc->caps.subvp_pstate_allow_width_us = 20;
-
+	dc->caps.subvp_vertical_int_margin_us = 30;
 	dc->caps.max_slave_planes = 1;
 	dc->caps.max_slave_yuv_planes = 1;
 	dc->caps.max_slave_rgb_planes = 1;