From 147fcd07ceba1e6fe3c3218387651656f4b6afe1 Mon Sep 17 00:00:00 2001 From: Yongqiang Sun Date: Thu, 23 Jan 2020 16:30:15 -0500 Subject: [PATCH] drm/amd/display: Limit minimum DPPCLK to 100MHz. [ Upstream commit 6c81917a0485ee2a1be0dc23321ac10ecfd9578b ] [Why] Underflow is observed when plug in a 4K@60 monitor with 1366x768 eDP due to DPPCLK is too low. [How] Limit minimum DPPCLK to 100MHz. Signed-off-by: Yongqiang Sun Reviewed-by: Eric Yang Acked-by: Bhawanpreet Lakha Signed-off-by: Alex Deucher Signed-off-by: Sasha Levin --- drivers/gpu/drm/amd/display/dc/clk_mgr/dcn21/rn_clk_mgr.c | 6 ++++++ 1 file changed, 6 insertions(+) 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 787f94d..dd92f9c 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 @@ -91,6 +91,12 @@ void rn_update_clocks(struct clk_mgr *clk_mgr_base, rn_vbios_smu_set_min_deep_sleep_dcfclk(clk_mgr, clk_mgr_base->clks.dcfclk_deep_sleep_khz); } + // workaround: Limit dppclk to 100Mhz to avoid lower eDP panel switch to plus 4K monitor underflow. + if (!IS_DIAG_DC(dc->ctx->dce_environment)) { + if (new_clocks->dppclk_khz < 100000) + 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) dpp_clock_lowered = true; -- 2.7.4