linux-kernel - [PATCH 5.4 06/85] ARM: dts: imx6qdl-sr-som: Increase the PHY reset duration to 10ms

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Date:   Tue, 10 Aug 2021 19:29:39 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Hervé Codina <herve.codina@...tlin.com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Shawn Guo <shawnguo@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 06/85] ARM: dts: imx6qdl-sr-som: Increase the PHY reset duration to 10ms

From: Maxime Chevallier <maxime.chevallier@...tlin.com>

[ Upstream commit fd8e83884fdd7b5fc411f201a58d8d01890198a2 ]

The AR803x PHY used on this modules seems to require the reset line to
be asserted for around 10ms in order to avoid rare cases where the PHY
gets stuck in an incoherent state that prevents it to function
correctly.

The previous value of 2ms was found to be problematic on some setups,
causing intermittent issues where the PHY would be unresponsive
every once in a while on some sytems, with a low occurrence (it typically
took around 30 consecutive reboots to encounter the issue).

Bumping the delay to the 10ms makes the issue dissapear, with more than
2500 consecutive reboots performed without the issue showing-up.

Fixes: 208d7baf8085 ("ARM: imx: initial SolidRun HummingBoard support")
Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
Tested-by: Hervé Codina <herve.codina@...tlin.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Signed-off-by: Shawn Guo <shawnguo@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm/boot/dts/imx6qdl-sr-som.dtsi | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/imx6qdl-sr-som.dtsi b/arch/arm/boot/dts/imx6qdl-sr-som.dtsi
index 6d7f6b9035bc..f2649241167e 100644
--- a/arch/arm/boot/dts/imx6qdl-sr-som.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-sr-som.dtsi
@@ -54,7 +54,13 @@
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_microsom_enet_ar8035>;
 	phy-mode = "rgmii-id";
-	phy-reset-duration = <2>;
+
+	/*
+	 * The PHY seems to require a long-enough reset duration to avoid
+	 * some rare issues where the PHY gets stuck in an inconsistent and
+	 * non-functional state at boot-up. 10ms proved to be fine .
+	 */
+	phy-reset-duration = <10>;
 	phy-reset-gpios = <&gpio4 15 GPIO_ACTIVE_LOW>;
 	status = "okay";
 };
-- 
2.30.2