PCIe ERR_NONFATAL errors mean a particular transaction is unreliable but
the Link is otherwise fully functional (PCIe r4.0, sec 6.2.2).

The AER driver handles these by logging the error details and calling
driver-supplied pci_error_handlers callbacks.  It does not reset downstream
devices, does not remove them from the PCI subsystem, does not re-enumerate
them, and does not call their driver .remove() or .probe() methods.

But DPC driver previously enabled DPC on ERR_NONFATAL, so if the hardware
supports DPC, these errors caused a Link reset (performed automatically by
the hardware), followed by the DPC driver removing affected devices (which
calls their .remove() methods), bringing the Link back up, and
re-enumerating (which calls driver .probe() methods).

Disable ERR_NONFATAL DPC triggering so these errors will only be handled by
AER.  This means drivers won't have to deal with different usage of their
pci_error_handlers callbacks and .probe() and .remove() methods based on
whether the platform has DPC support.

Signed-off-by: Oza Pawandeep <p...@codeaurora.org>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <helg...@kernel.org>

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 80ec384..361903f 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -260,7 +260,7 @@ static int dpc_probe(struct pcie_device *dev)
-       ctl = (ctl & 0xfff4) | PCI_EXP_DPC_CTL_EN_NONFATAL | 
+       ctl = (ctl & 0xfff4) | PCI_EXP_DPC_CTL_EN_FATAL | 
        pci_write_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL, ctl);
        dev_info(device, "DPC error containment capabilities: Int Msg #%d, 
RPExt%c PoisonedTLP%c SwTrigger%c RP PIO Log %d, DL_ActiveErr%c\n",
@@ -278,7 +278,7 @@ static void dpc_remove(struct pcie_device *dev)
        u16 ctl;
        pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL, &ctl);
        pci_write_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL, ctl);
diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
index 103ba79..5182e0d 100644
--- a/include/uapi/linux/pci_regs.h
+++ b/include/uapi/linux/pci_regs.h
@@ -981,6 +981,7 @@
 #define  PCI_EXP_DPC_CAP_DL_ACTIVE     0x1000  /* ERR_COR signal on DL_Active 
supported */
 #define PCI_EXP_DPC_CTL                        6       /* DPC control */
+#define  PCI_EXP_DPC_CTL_EN_FATAL      0x0001  /* Enable trigger on ERR_FATAL 
message */
 #define  PCI_EXP_DPC_CTL_EN_NONFATAL   0x0002  /* Enable trigger on 
ERR_NONFATAL message */
 #define  PCI_EXP_DPC_CTL_INT_EN        0x0008  /* DPC Interrupt Enable */

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