linux-kernel - [PATCH 8/8] PCI: qcom: Do not advertise hotplug capability for IP v2.1.0

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Message-Id: <20230506073139.8789-9-manivannan.sadhasivam@linaro.org>
Date:   Sat,  6 May 2023 13:01:39 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     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,
        quic_srichara@...cinc.com,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH 8/8] PCI: qcom: Do not advertise hotplug capability for IP v2.1.0

SoCs making use of Qcom PCIe controller IP v2.1.0 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 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 | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 6fbaf7b419e6..68af95c836d2 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -373,6 +373,7 @@ static int qcom_pcie_post_init_2_1_0(struct qcom_pcie *pcie)
 {
 	struct qcom_pcie_resources_2_1_0 *res = &pcie->res.v2_1_0;
 	struct dw_pcie *pci = pcie->pci;
+	u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
 	struct device *dev = pci->dev;
 	struct device_node *node = dev->of_node;
 	u32 val;
@@ -424,6 +425,14 @@ static int qcom_pcie_post_init_2_1_0(struct qcom_pcie *pcie)
 	writel(CFG_BRIDGE_SB_INIT,
 	       pci->dbi_base + AXI_MSTR_RESP_COMP_CTRL1);
 
+	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);
+
 	return 0;
 }
 
-- 
2.25.1