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From:   Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To:     lpieralisi@kernel.org, kw@linux.com, bhelgaas@google.com
Cc:     robh@kernel.org, andersson@kernel.org, konrad.dybcio@linaro.org,
        linux-pci@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-kernel@vger.kernel.org, steev@kali.org,
        quic_srichara@quicinc.com,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Subject: [PATCH v4 0/9] PCI: qcom: Do not advertise hotplug capability
Date:   Mon, 19 Jun 2023 20:33:59 +0530
Message-Id: <20230619150408.8468-1-manivannan.sadhasivam@linaro.org>
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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 v4:

* Splitted patch 1/8 into two
* Rebased on top of pci/next

Changes in v3:

* Dropped double signed-off tags
* Dropped Dmitry's gmail reviewed tag as per his request
* Mentioned the newline change in commit log of patch 2/8

Changes in v2:

* Collected tags
* Moved the HPC clearing to a separate function and reused across different
  configs

Manivannan Sadhasivam (9):
  PCI: qcom: Disable write access to read only registers for IP v2.3.3
  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(-)

-- 
2.25.1