linux-kernel - Re: [PATCH v4 08/11] PCI: qcom: Add support for PCIe pre/post_link_speed

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Message-ID: <b9647055-a9f2-4016-a7b1-81c15a0d82c1@oss.qualcomm.com>
Date: Sat, 12 Jul 2025 04:41:53 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Lorenzo Pieralisi
 <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>, Jeff Johnson <jjohnson@...nel.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, mhi@...ts.linux.dev,
        linux-wireless@...r.kernel.org, ath11k@...ts.infradead.org,
        qiang.yu@....qualcomm.com, quic_vbadigan@...cinc.com,
        quic_vpernami@...cinc.com, quic_mrana@...cinc.com,
        Jeff Johnson <jeff.johnson@....qualcomm.com>
Subject: Re: [PATCH v4 08/11] PCI: qcom: Add support for PCIe
 pre/post_link_speed_change()



On 7/12/2025 2:59 AM, Bjorn Helgaas wrote:
> On Mon, Jun 09, 2025 at 04:21:29PM +0530, Krishna Chaitanya Chundru wrote:
>> QCOM PCIe controllers need to disable ASPM before initiating link
>> re-train. So as part of pre_link_speed_change() disable ASPM and as
>> part of post_link_speed_change() enable ASPM back.
> 
> Is this a QCOM defect?  Or is there something in the PCIe spec about
This is QCOM issue only.
> needing to disable ASPM during retrain?  What about
> pcie_retrain_link()?  Does that work on QCOM?
After disabling ASPM will work pcie_retrain_link().

- Krishna Chaitanya.
> 
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -276,10 +276,16 @@ struct qcom_pcie {
>>   	struct dentry *debugfs;
>>   	bool suspended;
>>   	bool use_pm_opp;
>> +	int aspm_state; /* Store ASPM state used in pre & post link speed change */
> 
> Whatever this is, it's definitely not an int.  Some kind of unsigned
> thing of specified size, at least.