drm/amd/display: Cap certain DML values for Low Pix Clk on DCN2.1

[WHY]
In certain conditions with low pixel clock, some values in DML may go
past the max due to margining for latency hiding. This causes assertions
to get hit.

[HOW]
If the pixel clock is low and some values are high, cap it to the max.
Signed-off-by: Sung Lee <sung.lee@amd.com>
Reviewed-by: Dmytro Laktyushkin <Dmytro.Laktyushkin@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dml/dcn21/display_rq_dlg_calc_21.c

@@ -1490,12 +1490,20 @@ static void dml_rq_dlg_get_dlg_params(
 	disp_dlg_regs->refcyc_per_pte_group_vblank_l =
 			(unsigned int) (dst_y_per_row_vblank * (double) htotal
 					* ref_freq_to_pix_freq / (double) dpte_groups_per_row_ub_l);
+	if ((refclk_freq_in_mhz / ref_freq_to_pix_freq < 28) &&
+			disp_dlg_regs->refcyc_per_pte_group_vblank_l >= (unsigned int)dml_pow(2, 13))
+		disp_dlg_regs->refcyc_per_pte_group_vblank_l = (1 << 13) - 1;
+	else
 		ASSERT(disp_dlg_regs->refcyc_per_pte_group_vblank_l < (unsigned int)dml_pow(2, 13));
 
 	if (dual_plane) {
 		disp_dlg_regs->refcyc_per_pte_group_vblank_c = (unsigned int) (dst_y_per_row_vblank
 				* (double) htotal * ref_freq_to_pix_freq
 				/ (double) dpte_groups_per_row_ub_c);
+		if ((refclk_freq_in_mhz / ref_freq_to_pix_freq < 28) &&
+				disp_dlg_regs->refcyc_per_pte_group_vblank_c >= (unsigned int)dml_pow(2, 13))
+			disp_dlg_regs->refcyc_per_pte_group_vblank_c = (1 << 13) - 1;
+		else
 			ASSERT(disp_dlg_regs->refcyc_per_pte_group_vblank_c
 				< (unsigned int)dml_pow(2, 13));
 	}