drm/amd/display: fix FCLK pstate change underflow

[Why]
Currently we set FCLK p-state change
watermark calculated based on dummy
p-state latency when UCLK p-state is
not supported

[How]
Calculate FCLK p-state change watermark
based on on FCLK pstate change latency
in case UCLK p-state is not supported
Reviewed-by: Nevenko Stupar <Nevenko.Stupar@amd.com>
Acked-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Vladimir Stempen <vladimir.stempen@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/dcn32/dcn32_fpu.c

@@ -2126,6 +2126,10 @@ void dcn32_calculate_wm_and_dlg_fpu(struct dc *dc, struct dc_state *context,
 		 */
 		context->bw_ctx.bw.dcn.watermarks.a = context->bw_ctx.bw.dcn.watermarks.c;
 		context->bw_ctx.bw.dcn.watermarks.a.cstate_pstate.pstate_change_ns = 0;
+		/* Calculate FCLK p-state change watermark based on FCLK pstate change latency in case
+		 * UCLK p-state is not supported, to avoid underflow in case FCLK pstate is supported
+		 */
+		context->bw_ctx.bw.dcn.watermarks.a.cstate_pstate.fclk_pstate_change_ns = get_fclk_watermark(&context->bw_ctx.dml, pipes, pipe_cnt) * 1000;
 	} else {
 		/* Set A:
 		 * All clocks min.