linux-kernel - Re: [PATCH] phy: qcom: qmp-pcie: Fix PHY initialization when powered down by firmware

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Message-ID: <f44beed6-72c3-4e86-834b-ac522c786bc7@oss.qualcomm.com>
Date: Wed, 13 Aug 2025 12:13:31 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Stephan Gerhold <stephan.gerhold@...aro.org>,
        Vinod Koul <vkoul@...nel.org>
Cc: Kishon Vijay Abraham I <kishon@...nel.org>,
        Wenbin Yao <quic_wenbyao@...cinc.com>,
        Qiang Yu <qiang.yu@....qualcomm.com>,
        Manivannan Sadhasivam <mani@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH] phy: qcom: qmp-pcie: Fix PHY initialization when powered
 down by firmware

On 8/12/25 6:30 PM, Stephan Gerhold wrote:
> Commit 0cc22f5a861c ("phy: qcom: qmp-pcie: Add PHY register retention
> support") added support for using the "no_csr" reset to skip configuration
> of the PHY if the init sequence was already applied by the boot firmware.
> The expectation is that the PHY is only turned on/off by using the "no_csr"
> reset, instead of powering it down and re-programming it after a full
> reset.
> 
> The boot firmware on X1E does not fully conform to this expectation: If the
> PCIe3 link fails to come up (e.g. because no PCIe card is inserted), the
> firmware powers down the PHY using the QPHY_PCS_POWER_DOWN_CONTROL
> register. The QPHY_START_CTRL register is kept as-is, so the driver assumes
> the PHY is already initialized and skips the configuration/power up
> sequence. The PHY won't come up again without clearing the
> QPHY_PCS_POWER_DOWN_CONTROL, so eventually initialization fails:
> 
>   qcom-qmp-pcie-phy 1be0000.phy: phy initialization timed-out
>   phy phy-1be0000.phy.0: phy poweron failed --> -110
>   qcom-pcie 1bd0000.pcie: cannot initialize host
>   qcom-pcie 1bd0000.pcie: probe with driver qcom-pcie failed with error -110
> 
> This can be reliably reproduced on the X1E CRD, QCP and Devkit when no card
> is inserted for PCIe3.
> 
> Fix this by checking the QPHY_PCS_POWER_DOWN_CONTROL register in addition
> to QPHY_START_CTRL. If the PHY is powered down with the register, it
> doesn't conform to the expectations for using the "no_csr" reset, so we
> fully re-initialize with the normal reset sequence.
> 
> Cc: stable@...r.kernel.org
> Fixes: 0cc22f5a861c ("phy: qcom: qmp-pcie: Add PHY register retention support")
> Signed-off-by: Stephan Gerhold <stephan.gerhold@...aro.org>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> index 95830dcfdec9b1f68fd55d1cc3c102985cfafcc1..6a469a8f5ae7eba6e4d1d702efaae1c658c4321e 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> @@ -4339,10 +4339,12 @@ static int qmp_pcie_init(struct phy *phy)
>  	struct qmp_pcie *qmp = phy_get_drvdata(phy);
>  	const struct qmp_phy_cfg *cfg = qmp->cfg;
>  	void __iomem *pcs = qmp->pcs;
> -	bool phy_initialized = !!(readl(pcs + cfg->regs[QPHY_START_CTRL]));
>  	int ret;
>  
> -	qmp->skip_init = qmp->nocsr_reset && phy_initialized;
> +	qmp->skip_init = qmp->nocsr_reset &&
> +		readl(pcs + cfg->regs[QPHY_START_CTRL]) &&
> +		readl(pcs + cfg->regs[QPHY_PCS_POWER_DOWN_CONTROL]);

I think it would be good to ensure the value matches platform config
expectations, i.e. !(val & cfg->pwrdn_ctrl)

Konrad