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

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Message-ID: <aJx_KjWFxeYE5U81@linaro.org>
Date: Wed, 13 Aug 2025 14:04:00 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Vinod Koul <vkoul@...nel.org>,
	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 Wed, Aug 13, 2025 at 12:13:31PM +0200, Konrad Dybcio wrote:
> 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)
> 

I think ((val & cfg->pwrdn_ctrl) == cfg->pwrdn_ctrl) is what you want,
to check if all the bits we would set are actually set? That sounds
reasonable, I'll send a v2 with that soon.

I'll make the same change for QPHY_START_CTRL, to have it consistent
(checking for SERDES_START | PCS_START, which is what we would set).

Thanks,
Stephan