drm/amd/display: Raise dispclk value for dce120 by 15%

[Why]

The DISPCLK value was previously requested to be 15% higher for all
ASICs that went through the dce110 bandwidth code path. As part of a
refactoring of dce_clocks and the dce110 set bandwidth codepath this
was removed for power saving considerations.

That change caused display corruption under certain hardware
configurations with Vega10.

[How]

The 15% DISPCLK increase is brought back but only on dce110 for now.
This is should be a temporary workaround until the root cause is sorted
out for why this occurs on Vega (or other ASICs, if reported).
Tested-by: Nick Sarnie <sarnex@gentoo.org>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dce_clocks.c

@@ -468,6 +468,9 @@ static void dce12_update_clocks(struct dccg *dccg,
 {
 	struct dm_pp_clock_for_voltage_req clock_voltage_req = {0};
 
+	/* TODO: Investigate why this is needed to fix display corruption. */
+	new_clocks->dispclk_khz = new_clocks->dispclk_khz * 115 / 100;
+
 	if (should_set_clock(safe_to_lower, new_clocks->dispclk_khz, dccg->clks.dispclk_khz)) {
 		clock_voltage_req.clk_type = DM_PP_CLOCK_TYPE_DISPLAY_CLK;
 		clock_voltage_req.clocks_in_khz = new_clocks->dispclk_khz;