linux-kernel - Re: [PATCH v2 2/2] phy: freescale: imx8m-pcie: assert phy reset and perst in power off

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Message-ID: <Z8hw1W0PBsmanylZ@lizhi-Precision-Tower-5810>
Date: Wed, 5 Mar 2025 10:42:13 -0500
From: Frank Li <Frank.li@....com>
To: Stefan Eichenberger <eichest@...il.com>
Cc: 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, 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: Re: [PATCH v2 2/2] phy: freescale: imx8m-pcie: assert phy reset and
 perst in power off

On Wed, Mar 05, 2025 at 03:43:16PM +0100, Stefan Eichenberger wrote:
> 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>

Reviewed-by: Frank Li <Frank.Li@....com>

> ---
>  drivers/phy/freescale/phy-fsl-imx8m-pcie.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/phy/freescale/phy-fsl-imx8m-pcie.c b/drivers/phy/freescale/phy-fsl-imx8m-pcie.c
> index 5b505e34ca364..7355d9921b646 100644
> --- a/drivers/phy/freescale/phy-fsl-imx8m-pcie.c
> +++ b/drivers/phy/freescale/phy-fsl-imx8m-pcie.c
> @@ -156,6 +156,16 @@ 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);
> @@ -176,6 +186,7 @@ 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
>