linux-kernel - [PATCH 5.14 055/125] drm/amd/display: Fallback to clocks which meet requested voltage on DCN31

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Date:   Mon,  1 Nov 2021 10:17:08 +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, Michael Strauss <michael.strauss@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Alex Deucher <alexander.deucher@....com>
Subject: [PATCH 5.14 055/125] drm/amd/display: Fallback to clocks which meet requested voltage on DCN31

From: Michael Strauss <michael.strauss@....com>

commit 54149d13f369e1ab02f36b91feee02069184c1d8 upstream.

[WHY]
On certain configs, SMU clock table voltages don't match which cause parser
to behave incorrectly by leaving dcfclk and socclk table entries unpopulated.

[HOW]
Currently the function that finds the corresponding clock for a given voltage
only checks for exact voltage level matches. In the case that no match gets
found, parser now falls back to searching for the max clock which meets the
requested voltage (i.e. its corresponding voltage is below requested).

Signed-off-by: Michael Strauss <michael.strauss@....com>
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/amd/display/dc/clk_mgr/dcn31/dcn31_clk_mgr.c |   13 ++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn31/dcn31_clk_mgr.c
+++ b/drivers/gpu/drm/amd/display/dc/clk_mgr/dcn31/dcn31_clk_mgr.c
@@ -518,14 +518,21 @@ static unsigned int find_clk_for_voltage
 		unsigned int voltage)
 {
 	int i;
+	int max_voltage = 0;
+	int clock = 0;
 
 	for (i = 0; i < NUM_SOC_VOLTAGE_LEVELS; i++) {
-		if (clock_table->SocVoltage[i] == voltage)
+		if (clock_table->SocVoltage[i] == voltage) {
 			return clocks[i];
+		} else if (clock_table->SocVoltage[i] >= max_voltage &&
+				clock_table->SocVoltage[i] < voltage) {
+			max_voltage = clock_table->SocVoltage[i];
+			clock = clocks[i];
+		}
 	}
 
-	ASSERT(0);
-	return 0;
+	ASSERT(clock);
+	return clock;
 }
 
 void dcn31_clk_mgr_helper_populate_bw_params(