drm/amd/display: Init clock value by current vbios CLKs

[ Upstream commit 7e0b367 ]

[Why]
While booting into OS, driver updates DPP/DISP CLKs.
But init clock value is zero which is invalid.

[How]
Get current clocks value to update init clocks.
To avoid underflow.

Signed-off-by: Brandon Syu <Brandon.Syu@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c

@@ -97,8 +97,17 @@ void rn_update_clocks(struct clk_mgr *clk_mgr_base,
 			new_clocks->dppclk_khz = 100000;
 	}
 
-	if (should_set_clock(safe_to_lower, new_clocks->dppclk_khz, clk_mgr->base.clks.dppclk_khz)) {
-		if (clk_mgr->base.clks.dppclk_khz > new_clocks->dppclk_khz)
+	/*
+	 * Temporally ignore thew 0 cases for disp and dpp clks.
+	 * We may have a new feature that requires 0 clks in the future.
+	 */
+	if (new_clocks->dppclk_khz == 0 || new_clocks->dispclk_khz == 0) {
+		new_clocks->dppclk_khz = clk_mgr_base->clks.dppclk_khz;
+		new_clocks->dispclk_khz = clk_mgr_base->clks.dispclk_khz;
+	}
+
+	if (should_set_clock(safe_to_lower, new_clocks->dppclk_khz, clk_mgr_base->clks.dppclk_khz)) {
+		if (clk_mgr_base->clks.dppclk_khz > new_clocks->dppclk_khz)
 			dpp_clock_lowered = true;
 		clk_mgr_base->clks.dppclk_khz = new_clocks->dppclk_khz;
 		update_dppclk = true;