[PATCH 04/15] drm/amd/display: Don't compare dppclk before updating DTO

[Eryk Brol]

From: Alvin Lee <alvin.lee2 at amd.com>

[Why]
In dcn3_update_clocks there are situations where dppclk is not
lowered (i.e. stays the same), but DTO still needs to be increased
before we program pipe frontend (i.e. in prepare_bandwidth). If we
don't program the new DTO value before we program the pipe,
we will underflow as soon as the pipe lock is released until the
next call to dcn3_update_clocks where the DTO is updated.

[How]
Remove dppclk check before programming new DTO value.

Signed-off-by: Alvin Lee <alvin.lee2 at amd.com>
Reviewed-by: Jun Lei <Jun.Lei at amd.com>
Acked-by: Eryk Brol <eryk.brol at amd.com>
---
 .../gpu/drm/amd/display/dc/clk_mgr/dcn30/dcn30_clk_mgr.c   | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn30/dcn30_clk_mgr.c b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn30/dcn30_clk_mgr.c
index d8af56a58196..b0e9b0509568 100644
--- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn30/dcn30_clk_mgr.c
+++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn30/dcn30_clk_mgr.c
@@ -323,9 +323,10 @@ static void dcn3_update_clocks(struct clk_mgr *clk_mgr_base,
 			/* if clock is being raised, increase refclk before lowering DTO */
 			if (update_dppclk || update_dispclk)
 				dcn20_update_clocks_update_dentist(clk_mgr);
-			/* always update dtos unless clock is lowered and not safe to lower */
-			if (new_clocks->dppclk_khz >= dc->current_state->bw_ctx.bw.dcn.clk.dppclk_khz)
-				dcn20_update_clocks_update_dpp_dto(clk_mgr, context, safe_to_lower);
+			/* There is a check inside dcn20_update_clocks_update_dpp_dto which ensures
+			 * that we do not lower dto when it is not safe to lower. We do not need to
+			 * compare the current and new dppclk before calling this function.*/
+			dcn20_update_clocks_update_dpp_dto(clk_mgr, context, safe_to_lower);
 		}
 	}
 
-- 
2.25.1