linux-kernel - [PATCH 4.19 020/205] drm/amd/display: Raise dispclk value for dce120 by 15%

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Message-Id: <20181119162620.982335916@linuxfoundation.org>
Date:   Mon, 19 Nov 2018 17:25:27 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nick Sarnie <sarnex@...too.org>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Harry Wentland <Harry.Wentland@....com>,
        Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 020/205] drm/amd/display: Raise dispclk value for dce120 by 15%

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicholas Kazlauskas <nicholas.kazlauskas@....com>

[ Upstream commit 481f576c6c21bf0446eaa23623ef0262e9a5387c ]

[Why]

The DISPCLK value was previously requested to be 15% higher for all
ASICs that went through the dce110 bandwidth code path. As part of a
refactoring of dce_clocks and the dce110 set bandwidth codepath this
was removed for power saving considerations.

That change caused display corruption under certain hardware
configurations with Vega10.

[How]

The 15% DISPCLK increase is brought back but only on dce110 for now.
This is should be a temporary workaround until the root cause is sorted
out for why this occurs on Vega (or other ASICs, if reported).

Tested-by: Nick Sarnie <sarnex@...too.org>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Reviewed-by: Harry Wentland <Harry.Wentland@....com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/amd/display/dc/dce/dce_clocks.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/gpu/drm/amd/display/dc/dce/dce_clocks.c
+++ b/drivers/gpu/drm/amd/display/dc/dce/dce_clocks.c
@@ -466,6 +466,9 @@ static void dce12_update_clocks(struct d
 {
 	struct dm_pp_clock_for_voltage_req clock_voltage_req = {0};
 
+	/* TODO: Investigate why this is needed to fix display corruption. */
+	new_clocks->dispclk_khz = new_clocks->dispclk_khz * 115 / 100;
+
 	if (should_set_clock(safe_to_lower, new_clocks->dispclk_khz, dccg->clks.dispclk_khz)) {
 		clock_voltage_req.clk_type = DM_PP_CLOCK_TYPE_DISPLAY_CLK;
 		clock_voltage_req.clocks_in_khz = new_clocks->dispclk_khz;