PCI/MSI: Add MSIX option to write to ENTRY_DATA before any reads

Commit 7d5ec3d ("PCI/MSI: Mask all unused MSI-X entries") introduces a readl() from ENTRY_VECTOR_CTRL before the writel() to ENTRY_DATA. This is correct, however some hardware, like the Sun Neptune chips, the niu module, will cause an error and/or fatal trap if any MSIX table entry is read before the corresponding ENTRY_DATA field is written to. This patch adds an optional early writel() in msix_prepare_msi_desc(). Cc: [email protected] Signed-off-by: Jonathan Currier <[email protected]>
intel-lab-lkp · Nov 21, 2024 · 782b94f · 782b94f
1 parent 05b1367
commit 782b94f
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diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c
@@ -611,6 +611,8 @@ void msix_prepare_msi_desc(struct pci_dev *dev, struct msi_desc *desc)
 	if (desc->pci.msi_attrib.can_mask) {
 		void __iomem *addr = pci_msix_desc_addr(desc);
 
+		if (dev->dev_flags & PCI_DEV_FLAGS_MSIX_TOUCH_ENTRY_DATA_FIRST)
+			writel(0, addr + PCI_MSIX_ENTRY_DATA);
 		desc->pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
 	}
 }

diff --git a/include/linux/pci.h b/include/linux/pci.h
@@ -245,6 +245,8 @@ enum pci_dev_flags {
 	PCI_DEV_FLAGS_NO_RELAXED_ORDERING = (__force pci_dev_flags_t) (1 << 11),
 	/* Device does honor MSI masking despite saying otherwise */
 	PCI_DEV_FLAGS_HAS_MSI_MASKING = (__force pci_dev_flags_t) (1 << 12),
+	/* Device requires write to PCI_MSIX_ENTRY_DATA before any MSIX reads */
+	PCI_DEV_FLAGS_MSIX_TOUCH_ENTRY_DATA_FIRST = (__force pci_dev_flags_t) (1 << 13),
 };
 
 enum pci_irq_reroute_variant {