[PATCH v18 08/11] PCI/AER: Add pci_aer_raw_clear_status() to unconditionally clear Error Status

[sathyanarayanan.kuppuswamy@linux.intel.com]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Per the SFI _OSC and DPC Updates ECN [1] implementation note flowchart, the
OS seems to be expected to clear AER status even if it doesn't have
ownership of the AER capability.  Unlike the DPC capability, where a DPC
ECN [2] specifies a window when the OS is allowed to access DPC registers
even if it doesn't have ownership, there is no clear model for AER.

Add pci_aer_raw_clear_status() to clear the AER error status registers
unconditionally.  This is intended for use only by the EDR path (see [2]).

[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] Downstream Port Containment Related Enhancements ECN, Jan 28, 2019,
    affecting PCI Firmware Specification, Rev. 3.2
    https://members.pcisig.com/wg/PCI-SIG/document/12888
[bhelgaas: changelog]
Link: https://lore.kernel.org/r/29fb514a0d86e9bcc75cec4ea8474cd4db33adbf.1583286655.git.sathyanarayanan.kuppuswamy@linux.intel.com
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/pci/pci.h      |  2 ++
 drivers/pci/pcie/aer.c | 22 ++++++++++++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index e48677a0ba42..6d09bb22b73d 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -654,12 +654,14 @@ void pci_aer_exit(struct pci_dev *dev);
 extern const struct attribute_group aer_stats_attr_group;
 void pci_aer_clear_fatal_status(struct pci_dev *dev);
 void pci_aer_clear_device_status(struct pci_dev *dev);
+int pci_aer_raw_clear_status(struct pci_dev *dev);
 #else
 static inline void pci_no_aer(void) { }
 static inline void pci_aer_init(struct pci_dev *d) { }
 static inline void pci_aer_exit(struct pci_dev *d) { }
 static inline void pci_aer_clear_fatal_status(struct pci_dev *dev) { }
 static inline void pci_aer_clear_device_status(struct pci_dev *dev) { }
+static inline int pci_aer_raw_clear_status(struct pci_dev *dev) { return -EINVAL; }
 #endif
 
 #ifdef CONFIG_ACPI
diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index c0540c3761dc..bd9f122165e0 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -420,7 +420,16 @@ void pci_aer_clear_fatal_status(struct pci_dev *dev)
 		pci_write_config_dword(dev, pos + PCI_ERR_UNCOR_STATUS, status);
 }
 
-int pci_cleanup_aer_error_status_regs(struct pci_dev *dev)
+/**
+ * pci_aer_raw_clear_status - Clear AER error registers.
+ * @dev: the PCI device
+ *
+ * Clearing AER error status registers unconditionally, regardless of
+ * whether they're owned by firmware or the OS.
+ *
+ * Returns 0 on success, or negative on failure.
+ */
+int pci_aer_raw_clear_status(struct pci_dev *dev)
 {
 	int pos;
 	u32 status;
@@ -433,9 +442,6 @@ int pci_cleanup_aer_error_status_regs(struct pci_dev *dev)
 	if (!pos)
 		return -EIO;
 
-	if (pcie_aer_get_firmware_first(dev))
-		return -EIO;
-
 	port_type = pci_pcie_type(dev);
 	if (port_type == PCI_EXP_TYPE_ROOT_PORT) {
 		pci_read_config_dword(dev, pos + PCI_ERR_ROOT_STATUS, &status);
@@ -451,6 +457,14 @@ int pci_cleanup_aer_error_status_regs(struct pci_dev *dev)
 	return 0;
 }
 
+int pci_cleanup_aer_error_status_regs(struct pci_dev *dev)
+{
+	if (pcie_aer_get_firmware_first(dev))
+		return -EIO;
+
+	return pci_aer_raw_clear_status(dev);
+}
+
 void pci_save_aer_state(struct pci_dev *dev)
 {
 	struct pci_cap_saved_state *save_state;
-- 
2.17.1