linux-kernel - [PATCH v1 07/14] arm64: dts: imx8mq-librem5: Set the DVS voltages lower

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Message-Id: <20230309204608.237605-8-martin.kepplinger@puri.sm>
Date:   Thu,  9 Mar 2023 21:46:01 +0100
From:   Martin Kepplinger <martin.kepplinger@...i.sm>
To:     robh@...nel.org, krzysztof.kozlowski@...aro.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com
Cc:     kernel@...i.sm, linux-imx@....com, devicetree@...r.kernel.org,
        phone-devel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>,
        Martin Kepplinger <martin.kepplinger@...i.sm>
Subject: [PATCH v1 07/14] arm64: dts: imx8mq-librem5: Set the DVS voltages lower

From: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>

They're still in the operating range according to i.MX 8M Quad
datasheet. There's some headroom added over minimal values to
account for voltage drop.

Operational ranges (min - typ - max [selected]):
 - VDD_SOC (BUCK1): 0.81 - 0.9 - 0.99 [0.88]
 - VDD_ARM (BUCK2): 0.81 - 0.9 - 1.05 [0.84] (1000MHz)
                    0.90 - 1.0 - 1.05 [0.93] (1500MHz)
 - VDD_GPU (BUCK3): 0.81 - 0.9 - 1.05 [0.85] (800MHz)
                    0.90 - 1.0 - 1.05 [ -- ] (1000MHz)
 - VDD_VPU (BUCK4): 0.81 - 0.9 - 1.05 [ -- ] (550/500/588MHz)
                    0.90 - 1.0 - 1.05 [0.93] (660/600/800MHz)

Idle power consumption doesn't appear to be influenced much,
but a simple load test (`cat /dev/urandom | pigz - > /dev/null`
combined with running Animatch) seems to show about 0.3W of
difference.

Care is advised, as there may be differences between each
units in how low can they be undervolted - in my experience,
reaching that point usually makes the phone fail to boot.
In my case, it appears that my Birch phone can go down the most.

This is a somewhat conservative set of values that I've seen
working well on all my devices; I haven't tried very hard to
optimize it, so more experiments are welcome.

Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@...i.sm>
Signed-off-by: Martin Kepplinger <martin.kepplinger@...i.sm>
---
 .../boot/dts/freescale/imx8mq-librem5-r3.dts  |  2 +-
 .../boot/dts/freescale/imx8mq-librem5.dtsi    | 22 ++++++++++++++-----
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8mq-librem5-r3.dts b/arch/arm64/boot/dts/freescale/imx8mq-librem5-r3.dts
index 4533a84fb0b95..077c5cd2586f7 100644
--- a/arch/arm64/boot/dts/freescale/imx8mq-librem5-r3.dts
+++ b/arch/arm64/boot/dts/freescale/imx8mq-librem5-r3.dts
@@ -7,7 +7,7 @@
 
 &a53_opp_table {
 	opp-1000000000 {
-		opp-microvolt = <1000000>;
+		opp-microvolt = <950000>;
 	};
 };
 
diff --git a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
index 509776a63259b..eaf35cff2f8a6 100644
--- a/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mq-librem5.dtsi
@@ -839,8 +839,8 @@ buck1_reg: BUCK1 {
 				regulator-max-microvolt = <1300000>;
 				regulator-boot-on;
 				regulator-ramp-delay = <1250>;
-				rohm,dvs-run-voltage = <900000>;
-				rohm,dvs-idle-voltage = <850000>;
+				rohm,dvs-run-voltage = <880000>;
+				rohm,dvs-idle-voltage = <820000>;
 				rohm,dvs-suspend-voltage = <800000>;
 				regulator-always-on;
 			};
@@ -851,8 +851,8 @@ buck2_reg: BUCK2 {
 				regulator-max-microvolt = <1300000>;
 				regulator-boot-on;
 				regulator-ramp-delay = <1250>;
-				rohm,dvs-run-voltage = <1000000>;
-				rohm,dvs-idle-voltage = <900000>;
+				rohm,dvs-run-voltage = <950000>;
+				rohm,dvs-idle-voltage = <850000>;
 				regulator-always-on;
 			};
 
@@ -861,14 +861,14 @@ buck3_reg: BUCK3 {
 				regulator-min-microvolt = <700000>;
 				regulator-max-microvolt = <1300000>;
 				regulator-boot-on;
-				rohm,dvs-run-voltage = <900000>;
+				rohm,dvs-run-voltage = <850000>;
 			};
 
 			buck4_reg: BUCK4 {
 				regulator-name = "buck4";
 				regulator-min-microvolt = <700000>;
 				regulator-max-microvolt = <1300000>;
-				rohm,dvs-run-voltage = <1000000>;
+				rohm,dvs-run-voltage = <930000>;
 			};
 
 			buck5_reg: BUCK5 {
@@ -1403,3 +1403,13 @@ &wdog1 {
 	fsl,ext-reset-output;
 	status = "okay";
 };
+
+&a53_opp_table {
+	opp-1000000000 {
+		opp-microvolt = <850000>;
+	};
+
+	opp-1500000000 {
+		opp-microvolt = <950000>;
+	};
+};
-- 
2.30.2