PCI: cadence-ep: Correct PBA offset in .set_msix() callback

While cdns_pcie_ep_set_msix() writes the Table Size field correctly (N-1),
the calculation of the PBA offset is wrong because it calculates space for
(N-1) entries instead of N.

This results in the following QEMU error when using PCI passthrough on a
device which relies on the PCI endpoint subsystem:

  failed to add PCI capability 0x11[0x50]@0xb0: table & pba overlap, or they don't fit in BARs, or don't align

Fix the calculation of PBA offset in the MSI-X capability.

[bhelgaas: more specific subject and commit log]

Fixes: 3ef5d16f50f8 ("PCI: cadence: Add MSI-X support to Endpoint driver")
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20250514074313.283156-10-cassel@kernel.org

diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
index 599ec4b1223e9d586750f9b7f9a7cf16e03abf4f..112ae200b393a66ac3d5cb3780016354a88cd275 100644 (file)
--- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
@@ -292,13 +292,14 @@ static int cdns_pcie_ep_set_msix(struct pci_epc *epc, u8 fn, u8 vfn,
        struct cdns_pcie *pcie = &ep->pcie;
        u32 cap = CDNS_PCIE_EP_FUNC_MSIX_CAP_OFFSET;
        u32 val, reg;
+       u16 actual_interrupts = interrupts + 1;
 
        fn = cdns_pcie_get_fn_from_vfn(pcie, fn, vfn);
 
        reg = cap + PCI_MSIX_FLAGS;
        val = cdns_pcie_ep_fn_readw(pcie, fn, reg);
        val &= ~PCI_MSIX_FLAGS_QSIZE;
-       val |= interrupts;
+       val |= interrupts; /* 0's based value */
        cdns_pcie_ep_fn_writew(pcie, fn, reg, val);
 
        /* Set MSI-X BAR and offset */
@@ -308,7 +309,7 @@ static int cdns_pcie_ep_set_msix(struct pci_epc *epc, u8 fn, u8 vfn,
 
        /* Set PBA BAR and offset.  BAR must match MSI-X BAR */
        reg = cap + PCI_MSIX_PBA;
-       val = (offset + (interrupts * PCI_MSIX_ENTRY_SIZE)) | bir;
+       val = (offset + (actual_interrupts * PCI_MSIX_ENTRY_SIZE)) | bir;
        cdns_pcie_ep_fn_writel(pcie, fn, reg, val);
 
        return 0;