linux-kernel - [PATCH AUTOSEL 5.8 093/132] drm/amd/display: Avoid set zero in the requested clk

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Message-Id: <20201026235205.1023962-93-sashal@kernel.org>
Date:   Mon, 26 Oct 2020 19:51:25 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Eryk Brol <eryk.brol@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.8 093/132] drm/amd/display: Avoid set zero in the requested clk

From: Rodrigo Siqueira <Rodrigo.Siqueira@....com>

[ Upstream commit 2f8be0e516803cc3fd87c1671247896571a5a8fb ]

[Why]
Sometimes CRTCs can be disabled due to display unplugging or temporarily
transition in the userspace; in these circumstances, DCE tries to set
the minimum clock threshold. When we have this situation, the function
bw_calcs is invoked with number_of_displays set to zero, making DCE set
dispclk_khz and sclk_khz to zero. For these reasons, we have seen some
ATOM bios errors that look like:

[drm:atom_op_jump [amdgpu]] *ERROR* atombios stuck in loop for more than
5secs aborting
[drm:amdgpu_atom_execute_table_locked [amdgpu]] *ERROR* atombios stuck
executing EA8A (len 761, WS 0, PS 0) @ 0xEABA

[How]
This error happens due to an attempt to optimize the bandwidth using the
sclk, and the dispclk clock set to zero. Technically we handle this in
the function dce112_set_clock, but we are not considering the case that
this value is set to zero. This commit fixes this issue by ensuring that
we never set a minimum value below the minimum clock threshold.

Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@....com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Acked-by: Eryk Brol <eryk.brol@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/clk_mgr/dce112/dce112_clk_mgr.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/clk_mgr/dce112/dce112_clk_mgr.c b/drivers/gpu/drm/amd/display/dc/clk_mgr/dce112/dce112_clk_mgr.c
index d031bd3d30724..807dca8f7d7aa 100644
--- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dce112/dce112_clk_mgr.c
+++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dce112/dce112_clk_mgr.c
@@ -79,8 +79,7 @@ int dce112_set_clock(struct clk_mgr *clk_mgr_base, int requested_clk_khz)
 	memset(&dce_clk_params, 0, sizeof(dce_clk_params));
 
 	/* Make sure requested clock isn't lower than minimum threshold*/
-	if (requested_clk_khz > 0)
-		requested_clk_khz = max(requested_clk_khz,
+	requested_clk_khz = max(requested_clk_khz,
 				clk_mgr_dce->base.dentist_vco_freq_khz / 62);
 
 	dce_clk_params.target_clock_frequency = requested_clk_khz;
-- 
2.25.1