linux-kernel - Re: [PATCH v2 0/8] PCI: qcom: Do not advertise hotplug capability

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Message-ID: <ZGsvXbiWK383zoaQ@lpieralisi>
Date:   Mon, 22 May 2023 11:01:17 +0200
From:   Lorenzo Pieralisi <lpieralisi@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     kw@...ux.com, bhelgaas@...gle.com, 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,
        quic_srichara@...cinc.com, dmitry.baryshkov@...aro.org
Subject: Re: [PATCH v2 0/8] PCI: qcom: Do not advertise hotplug capability

On Fri, May 19, 2023 at 08:01:09PM +0530, Manivannan Sadhasivam wrote:
> Hi,
> 
> The SoCs making use of Qualcomm PCIe controllers do not support the PCIe 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, this series clears the HPC bit in PCI_EXP_SLTCAP
> register as a part of the post init sequence for all IP versions to not
> advertise the hotplug capability for the controller.
> 
> Testing
> =======
> 
> This series has been tested on DB845c (SDM845 SoC) and Lenovo Thinkpad X13s
> (SC8280XP SoC).
> 
> Thanks,
> Mani
> 
> Changes in v2:
> 
> * Collected tags
> * Moved the HPC clearing to a separate function and reused across different
>   configs
> 
> Manivannan Sadhasivam (8):
>   PCI: qcom: Use DWC helpers for modifying the read-only DBI registers
>   PCI: qcom: Disable write access to read only registers for IP v2.9.0
>   PCI: qcom: Do not advertise hotplug capability for IPs v2.7.0 and
>     v1.9.0
>   PCI: qcom: Do not advertise hotplug capability for IPs v2.3.3 and
>     v2.9.0
>   PCI: qcom: Do not advertise hotplug capability for IP v2.3.2
>   PCI: qcom: Use post init sequence of IP v2.3.2 for v2.4.0
>   PCI: qcom: Do not advertise hotplug capability for IP v1.0.0
>   PCI: qcom: Do not advertise hotplug capability for IP v2.1.0
> 
>  drivers/pci/controller/dwc/pcie-qcom.c | 73 ++++++++++++++------------
>  1 file changed, 38 insertions(+), 35 deletions(-)
> 

Some patches are signed-off twice, FYI, I can fix that while
applying.

Lorenzo

> -- 
> 2.25.1
>