linux-kernel - Re: [PATCH 5/8] PCI: qcom: Do not advertise hotplug capability for IP v2.3.2

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Message-ID: <0e5f9f6b-eb67-38f8-2719-06aa8fe296bd@linaro.org>
Date:   Sat, 6 May 2023 16:01:43 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        lpieralisi@...nel.org, kw@...ux.com, bhelgaas@...gle.com
Cc:     robh@...nel.org, andersson@...nel.org, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        steev@...i.org, quic_srichara@...cinc.com
Subject: Re: [PATCH 5/8] PCI: qcom: Do not advertise hotplug capability for IP
 v2.3.2



On 6.05.2023 14:04, Dmitry Baryshkov wrote:
> On 06/05/2023 10:31, Manivannan Sadhasivam wrote:
>> SoCs making use of Qcom PCIe controller IP v2.3.2 do not support hotplug
>> functionality. But the hotplug capability bit is set by default in the
>> hardware. This causes the kernel PCI core to register hotplug service for
>> the controller and send hotplug commands to it. But those commands will
>> timeout generating messages as below during boot and suspend/resume.
>>
>> [    5.782159] pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x03c0 (issued 2020 msec ago)
>> [    5.810161] pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x03c0 (issued 2048 msec ago)
>> [    7.838162] pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x07c0 (issued 2020 msec ago)
>> [    7.870159] pcieport 0001:00:00.0: pciehp: Timeout on hotplug command 0x07c0 (issued 2052 msec ago)
>>
>> This not only spams the console output but also induces a delay of a
>> couple of seconds. To fix this issue, let's clear the HPC bit in
>> PCI_EXP_SLTCAP register as a part of the post init sequence to not
>> advertise the hotplug capability for the controller.
>>
>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>> ---
>>   drivers/pci/controller/dwc/pcie-qcom.c | 10 ++++++++++
>>   1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>> index 3d5b3ce9e2da..33353be396ec 100644
>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>> @@ -579,6 +579,8 @@ static int qcom_pcie_init_2_3_2(struct qcom_pcie *pcie)
>>     static int qcom_pcie_post_init_2_3_2(struct qcom_pcie *pcie)
>>   {
>> +    struct dw_pcie *pci = pcie->pci;
>> +    u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>>       u32 val;
>>         /* enable PCIe clocks and resets */
>> @@ -602,6 +604,14 @@ static int qcom_pcie_post_init_2_3_2(struct qcom_pcie *pcie)
>>       val |= EN;
>>       writel(val, pcie->parf + PARF_AXI_MSTR_WR_ADDR_HALT_V2);
>>   +    dw_pcie_dbi_ro_wr_en(pci);
>> +
>> +    val = readl(pci->dbi_base + offset + PCI_EXP_SLTCAP);
>> +    val &= ~PCI_EXP_SLTCAP_HPC;
>> +    writel(val, pci->dbi_base + offset + PCI_EXP_SLTCAP);
>> +
>> +    dw_pcie_dbi_ro_wr_dis(pci);
>> +
> 
> Seeing this code again and again makes me wonder if we should have a separate function for this.
Moreover, is there no generic rmw type function for readl+writel?

Konrad
>