phy: freescale: imx8m-pcie: assert phy reset and perst in power off

commit aecb63e88c5e5fb9afb782a1577264c76f179af9 upstream.

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@vger.kernel.org
Fixes: 1aa97b0022 ("phy: freescale: pcie: Initialize the imx8 pcie standalone phy driver")
Signed-off-by: Stefan Eichenberger <stefan.eichenberger@toradex.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20250305144355.20364-3-eichest@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/phy/freescale/phy-fsl-imx8m-pcie.c

@@ -162,6 +162,16 @@ 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);
+	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);
@@ -182,6 +192,7 @@ 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,
 };