[tip: irq/msi] PCI/TPH: Replace the broken MSI-X control word update

tip-bot2 for Thomas Gleixner
2025-04-07T14:31:43Z

The following commit has been merged into the irq/msi branch of tip:

Commit-ID: a822d6e2d5228e45b6d03680b1a92b295864b285
Gitweb: https://git.kernel.org/tip/a822d6e2d5228e45b6d03680b1a92b295864b285
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 19 Mar 2025 11:56:58 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Mon, 07 Apr 2025 16:24:56 +02:00

PCI/TPH: Replace the broken MSI-X control word update

The driver walks the MSI descriptors to test whether a descriptor exists
for a given index. That's just abuse of the MSI internals.

The same test can be done with a single function call by looking up whether
there is a Linux interrupt number assigned at the index.

What's worse is that the function is completely unserialized against
modifications of the MSI-X control by operations issued from the interrupt
core. It also brings the PCI/MSI-X internal cached control word out of
sync.

Remove the trainwreck and invoke the function provided by the PCI/MSI core
to update it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/all/20250319105506.744271447@linutronix.de

---
drivers/pci/tph.c | 44 +-------------------------------------------
1 file changed, 1 insertion(+), 43 deletions(-)

diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
index 07de59c..77fce5e 100644
--- a/drivers/pci/tph.c
+++ b/drivers/pci/tph.c
@@ -204,48 +204,6 @@ static u8 get_rp_completer_type(struct pci_dev *pdev)
return FIELD_GET(PCI_EXP_DEVCAP2_TPH_COMP_MASK, reg);
}

-/* Write ST to MSI-X vector control reg - Return 0 if OK, otherwise -errno */
-static int write_tag_to_msix(struct pci_dev *pdev, int msix_idx, u16 tag)
-{
-#ifdef CONFIG_PCI_MSI
- struct msi_desc *msi_desc = NULL;
- void __iomem *vec_ctrl;
- u32 val;
- int err = 0;
-
- msi_lock_descs(&pdev->dev);
-
- /* Find the msi_desc entry with matching msix_idx */
- msi_for_each_desc(msi_desc, &pdev->dev, MSI_DESC_ASSOCIATED) {
- if (msi_desc->msi_index == msix_idx)
- break;
- }
-
- if (!msi_desc) {
- err = -ENXIO;
- goto err_out;
- }
-
- /* Get the vector control register (offset 0xc) pointed by msix_idx */
- vec_ctrl = pdev->msix_base + msix_idx * PCI_MSIX_ENTRY_SIZE;
- vec_ctrl += PCI_MSIX_ENTRY_VECTOR_CTRL;
-
- val = readl(vec_ctrl);
- val &= ~PCI_MSIX_ENTRY_CTRL_ST;
- val |= FIELD_PREP(PCI_MSIX_ENTRY_CTRL_ST, tag);
- writel(val, vec_ctrl);
-
- /* Read back to flush the update */
- val = readl(vec_ctrl);
-
-err_out:
- msi_unlock_descs(&pdev->dev);
- return err;
-#else
- return -ENODEV;
-#endif
-}
-
/* Write tag to ST table - Return 0 if OK, otherwise -errno */
static int write_tag_to_st_table(struct pci_dev *pdev, int index, u16 tag)
{
@@ -346,7 +304,7 @@ int pcie_tph_set_st_entry(struct pci_dev *pdev, unsigned int index, u16 tag)

switch (loc) {
case PCI_TPH_LOC_MSIX:
- err = write_tag_to_msix(pdev, index, tag);
+ err = pci_msix_write_tph_tag(pdev, index, tag);
break;
case PCI_TPH_LOC_CAP:
err = write_tag_to_st_table(pdev, index, tag);