linux-kernel - Re: [PATCH 4/8] PCI: qcom: Do not advertise hotplug capability for IPs v2.3.3 and v2.9.0

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Message-ID: <36fd2413-8a2a-5b7e-c4a0-64e0ac4622ed@quicinc.com>
Date:   Fri, 19 May 2023 18:13:43 +0530
From:   Sricharan Ramabadhran <quic_srichara@...cinc.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        <lpieralisi@...nel.org>, <kw@...ux.com>, <bhelgaas@...gle.com>
CC:     <robh@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <linux-pci@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <steev@...i.org>
Subject: Re: [PATCH 4/8] PCI: qcom: Do not advertise hotplug capability for
 IPs v2.3.3 and v2.9.0



On 5/6/2023 1:01 PM, Manivannan Sadhasivam wrote:
> SoCs making use of Qcom PCIe controller IPs v2.3.3 and v2.9.0 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 not set 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 | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 00246726c21d..3d5b3ce9e2da 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -140,7 +140,6 @@
>   						PCI_EXP_SLTCAP_AIP | \
>   						PCI_EXP_SLTCAP_PIP | \
>   						PCI_EXP_SLTCAP_HPS | \
> -						PCI_EXP_SLTCAP_HPC | \
>   						PCI_EXP_SLTCAP_EIP | \
>   						PCIE_CAP_SLOT_POWER_LIMIT_VAL | \
>   						PCIE_CAP_SLOT_POWER_LIMIT_SCALE)

  Tested this in ipq9574 board and the 'timeout' messages go away with
  this.

   Tested-by: Sricharan Ramabadhran <quic_srichara@...cinc.com>

Regards,
  Sricharan