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

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Message-ID: <3ad5abef-9fcd-4dbd-babd-3820f6915a52@oss.qualcomm.com>
Date: Wed, 13 Aug 2025 14:07:56 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Stephan Gerhold <stephan.gerhold@...aro.org>
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 8/13/25 2:04 PM, Stephan Gerhold wrote:
> 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.

We can do that, currently the register (at least on 8750 that I randomly
checked) doesn't have any other bits..

> 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).

Sounds reasonable

Konrad