drm/amd/display: Set compbuf size to min at prep prevent overbook crb

[Why]
Detbuffer size is dynamically set for dcn31x. At certain moment,
compbuf+(def size * num pipes) > config return buffer size causing
flickering. This is easily reproducible when MPO is
enabled with two displays.

[How]
At prepare BW, use the min comp buffer size. When it is to
optimize BW, set compbuf size back to maximum possible size.
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Solomon Chiu <solomon.chiu@amd.com>
Signed-off-by: Duncan Ma <duncanma@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/dcn20/dcn20_hwseq.c

@@ -1818,6 +1818,7 @@ void dcn20_prepare_bandwidth(
 		struct dc_state *context)
 {
 	struct hubbub *hubbub = dc->res_pool->hubbub;
+	unsigned int compbuf_size_kb = 0;
 
 	dc->clk_mgr->funcs->update_clocks(
 			dc->clk_mgr,
@@ -1829,9 +1830,16 @@ void dcn20_prepare_bandwidth(
 					&context->bw_ctx.bw.dcn.watermarks,
 					dc->res_pool->ref_clocks.dchub_ref_clock_inKhz / 1000,
 					false);
+
 	/* decrease compbuf size */
-	if (hubbub->funcs->program_compbuf_size)
-		hubbub->funcs->program_compbuf_size(hubbub, context->bw_ctx.bw.dcn.compbuf_size_kb, false);
+	if (hubbub->funcs->program_compbuf_size) {
+		if (context->bw_ctx.dml.ip.min_comp_buffer_size_kbytes)
+			compbuf_size_kb = context->bw_ctx.dml.ip.min_comp_buffer_size_kbytes;
+		else
+			compbuf_size_kb = context->bw_ctx.bw.dcn.compbuf_size_kb;
+
+		hubbub->funcs->program_compbuf_size(hubbub, compbuf_size_kb, false);
+	}
 }
 
 void dcn20_optimize_bandwidth(

drivers/gpu/drm/amd/display/dc/dml/display_mode_structs.h

@@ -141,6 +141,7 @@ struct _vcs_dpi_ip_params_st {
 	unsigned int odm_capable;
 	unsigned int rob_buffer_size_kbytes;
 	unsigned int det_buffer_size_kbytes;
+	unsigned int min_comp_buffer_size_kbytes;
 	unsigned int dpte_buffer_size_in_pte_reqs_luma;
 	unsigned int dpte_buffer_size_in_pte_reqs_chroma;
 	unsigned int pde_proc_buffer_size_64k_reqs;