From: Brandon Syu <brandon....@amd.com>

[ Upstream commit 7e0b367db85ef7b91399006253759a024eab7653 ]

[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....@amd.com>
Reviewed-by: Tony Cheng <tony.ch...@amd.com>
Acked-by: Aurabindo Pillai <aurabindo.pil...@amd.com>
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 .../drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c   | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c 
b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c
index dd92f9c295b45..9f301f8575a54 100644
--- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c
+++ b/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;
-- 
2.27.0



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