[PATCH V3] AER: aer_root_reset() non-native handling

[Sean V Kelley]

If an OS has not been granted AER control via _OSC, then
the OS should not make changes to PCI_ERR_ROOT_COMMAND and
PCI_ERR_ROOT_STATUS related registers. Per section 4.5.1 of
the System Firmware Intermediary (SFI) _OSC and DPC Updates
ECN [1], this bit also covers these aspects of the PCI
Express Advanced Error Reporting. Based on the above and
earlier discussion [2], make the following changes:

Add a check for the native case (i.e., AER control via _OSC)

Note that the current "clear, reset, enable" order suggests that the
reset might cause errors that we should ignore. Lacking historical
context, these will be retained.

[1] System Firmware Intermediary (SFI) _OSC and DPC Updates ECN, Feb 24,
    2020, affecting PCI Firmware Specification, Rev. 3.2
    https://members.pcisig.com/wg/PCI-SIG/document/14076
[2] 
https://lore.kernel.org/linux-pci/20201020162820.GA370938@bjorn-Precision-5520/

Signed-off-by: Sean V Kelley <sean.v.kel...@intel.com>
---
Changes since V2 :

Fixed an unfortunate copy/paste error.

Changes since V1 [1]:

Noted lack of historical context on isolation of both the
pci_bus_error_reset() and the clearing of Root Error Status. In fact,
the call to aer_enable_rootport() likewise disables system error generation
in response to error messages around the clearing of the error status. So
retained the wrapping of the  "clear, reset, enable".

[1] 
https://lore.kernel.org/linux-pci/20201030223443.165783-1-sean.v.kel...@intel.com/

Thanks,

Sean
---
 drivers/pci/pcie/aer.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index 65dff5f3457a..4ab379fa1506 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -1358,26 +1358,29 @@ static int aer_probe(struct pcie_device *dev)
 static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
 {
        int aer = dev->aer_cap;
+       int rc = 0;
        u32 reg32;
-       int rc;
-

-       /* Disable Root's interrupt in response to error messages */
-       pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
-       reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
-       pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
+       if (pcie_aer_is_native(dev)) {
+               /* Disable Root's interrupt in response to error messages */
+               pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
+               reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
+               pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
+       }

        rc = pci_bus_error_reset(dev);
-       pci_info(dev, "Root Port link has been reset\n");
+       pci_info(dev, "Root Port link has been reset (%d)\n", rc);

-       /* Clear Root Error Status */
-       pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, &reg32);
-       pci_write_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, reg32);
+       if (pcie_aer_is_native(dev)) {
+               /* Clear Root Error Status */
+               pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, &reg32);
+               pci_write_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, reg32);

-       /* Enable Root Port's interrupt in response to error messages */
-       pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
-       reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
-       pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
+               /* Enable Root Port's interrupt in response to error messages */
+               pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
+               reg32 |= ROOT_PORT_INTR_ON_MESG_MASK;
+               pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
+       }

        return rc ? PCI_ERS_RESULT_DISCONNECT : PCI_ERS_RESULT_RECOVERED;
 }
--
2.29.2