linux-kernel - [PATCH 4/5] PCI: qcom: Remove MSI-X Capability for Root Ports

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Message-Id: <20251109-remove_cap-v1-4-2208f46f4dc2@oss.qualcomm.com>
Date: Sun, 09 Nov 2025 22:59:43 -0800
From: Qiang Yu <qiang.yu@....qualcomm.com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        Manivannan Sadhasivam <mani@...nel.org>, Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>, Jingoo Han <jingoohan1@...il.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, Qiang Yu <qiang.yu@....qualcomm.com>
Subject: [PATCH 4/5] PCI: qcom: Remove MSI-X Capability for Root Ports

On some platforms like Glymur, the hardware does not support MSI-X in RC
mode, yet still exposes the MSI-X capability. However, it omits the
required MSI-X Table and PBA structures.

This mismatch can lead to issues where the PCIe port driver requests MSI-X
instead of MSI, causing the Root Port to trigger interrupts by writing to
an uninitialized address, resulting in SMMU faults.

To address this, remove MSI-X capability unconditionally for Root Ports.

Signed-off-by: Qiang Yu <qiang.yu@....qualcomm.com>
---
 drivers/pci/controller/dwc/pcie-qcom.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
index 805edbbfe7eba496bc99ca82051dee43d240f359..09443ffbb150e9c91bfd3b2adf15286ef2f00a2a 100644
--- a/drivers/pci/controller/dwc/pcie-qcom.c
+++ b/drivers/pci/controller/dwc/pcie-qcom.c
@@ -1350,6 +1350,8 @@ static int qcom_pcie_host_init(struct dw_pcie_rp *pp)
 			goto err_disable_phy;
 	}
 
+	dw_pcie_remove_capability(pcie->pci, PCI_CAP_ID_MSIX);
+
 	qcom_ep_reset_deassert(pcie);
 
 	if (pcie->cfg->ops->config_sid) {

-- 
2.34.1