linux-kernel - [PATCH v1 2/2] phy: freescale: imx8m-pcie: assert phy reset and perst in power off

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Message-ID: <20250228103959.47419-3-eichest@gmail.com>
Date: Fri, 28 Feb 2025 11:38:34 +0100
From: Stefan Eichenberger <eichest@...il.com>
To: vkoul@...nel.org,
	kishon@...nel.org,
	shawnguo@...nel.org,
	s.hauer@...gutronix.de,
	kernel@...gutronix.de,
	festevam@...il.com,
	p.zabel@...gutronix.de,
	tharvey@...eworks.com,
	hongxing.zhu@....com,
	francesco.dolcini@...adex.com
Cc: linux-phy@...ts.infradead.org,
	imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Stefan Eichenberger <stefan.eichenberger@...adex.com>,
	stable@...r.kernel.org
Subject: [PATCH v1 2/2] phy: freescale: imx8m-pcie: assert phy reset and perst in power off

From: Stefan Eichenberger <stefan.eichenberger@...adex.com>

Ensure the PHY reset and perst is asserted during power-off to
guarantee it is in a reset state upon repeated power-on calls. This
resolves an issue where the PHY may not properly initialize during
subsequent power-on cycles. Power-on will deassert the reset at the
appropriate time after tuning the PHY parameters.

During suspend/resume cycles, we observed that the PHY PLL failed to
lock during resume when the CPU temperature increased from 65C to 75C.
The observed errors were:
  phy phy-32f00000.pcie-phy.3: phy poweron failed --> -110
  imx6q-pcie 33800000.pcie: waiting for PHY ready timeout!
  imx6q-pcie 33800000.pcie: PM: dpm_run_callback(): genpd_resume_noirq+0x0/0x80 returns -110
  imx6q-pcie 33800000.pcie: PM: failed to resume noirq: error -110

This resulted in a complete CPU freeze, which is resolved by ensuring
the PHY is in reset during power-on, thus preventing PHY PLL failures.

Cc: stable@...r.kernel.org
Fixes: 1aa97b002258 ("phy: freescale: pcie: Initialize the imx8 pcie standalone phy driver")
Signed-off-by: Stefan Eichenberger <stefan.eichenberger@...adex.com>
---
 drivers/phy/freescale/phy-fsl-imx8m-pcie.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/phy/freescale/phy-fsl-imx8m-pcie.c b/drivers/phy/freescale/phy-fsl-imx8m-pcie.c
index 00f957a42d9dc..36bef416618de 100644
--- a/drivers/phy/freescale/phy-fsl-imx8m-pcie.c
+++ b/drivers/phy/freescale/phy-fsl-imx8m-pcie.c
@@ -158,6 +158,17 @@ static int imx8_pcie_phy_power_on(struct phy *phy)
 	return ret;
 }

+static int imx8_pcie_phy_power_off(struct phy *phy)
+{
+	struct imx8_pcie_phy *imx8_phy = phy_get_drvdata(phy);
+
+	reset_control_assert(imx8_phy->reset);
+	if (imx8_phy->perst)
+		reset_control_assert(imx8_phy->perst);
+
+	return 0;
+}
+
 static int imx8_pcie_phy_init(struct phy *phy)
 {
 	struct imx8_pcie_phy *imx8_phy = phy_get_drvdata(phy);
@@ -178,6 +189,7 @@ static const struct phy_ops imx8_pcie_phy_ops = {
 	.init		= imx8_pcie_phy_init,
 	.exit		= imx8_pcie_phy_exit,
 	.power_on	= imx8_pcie_phy_power_on,
+	.power_off	= imx8_pcie_phy_power_off,
 	.owner		= THIS_MODULE,
 };

-- 
2.45.2