PCI/AER: Add optional logging callback for correctable error

Some new devices such as CXL devices may want to record additional error
information on a corrected error. Add a callback to allow the PCI device
driver to do additional logging such as providing additional stats for user
space RAS monitoring.

For CXL device, this is actually a need due to CXL needing to write to the
CXL RAS capability structure correctable error status register in order to
clear the unmasked correctable errors. See CXL spec rev3.0 8.2.4.16.

Suggested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/166984619233.2804404.3966368388544312674.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Documentation/PCI/pci-error-recovery.rst

@@ -83,6 +83,7 @@ This structure has the form::
 		int (*mmio_enabled)(struct pci_dev *dev);
 		int (*slot_reset)(struct pci_dev *dev);
 		void (*resume)(struct pci_dev *dev);
+		void (*cor_error_detected)(struct pci_dev *dev);
 	};
 
 The possible channel states are::
@@ -422,5 +423,11 @@ That is, the recovery API only requires that:
    - drivers/net/cxgb3
    - drivers/net/s2io.c
 
+   The cor_error_detected() callback is invoked in handle_error_source() when
+   the error severity is "correctable". The callback is optional and allows
+   additional logging to be done if desired. See example:
+
+   - drivers/cxl/pci.c
+
 The End
 -------

drivers/pci/pcie/aer.c

@@ -961,8 +961,14 @@ static void handle_error_source(struct pci_dev *dev, struct aer_err_info *info)
 		if (aer)
 			pci_write_config_dword(dev, aer + PCI_ERR_COR_STATUS,
 					info->status);
-		if (pcie_aer_is_native(dev))
+		if (pcie_aer_is_native(dev)) {
+			struct pci_driver *pdrv = dev->driver;
+
+			if (pdrv && pdrv->err_handler &&
+			    pdrv->err_handler->cor_error_detected)
+				pdrv->err_handler->cor_error_detected(dev);
 			pcie_clear_device_status(dev);
+		}
 	} else if (info->severity == AER_NONFATAL)
 		pcie_do_recovery(dev, pci_channel_io_normal, aer_root_reset);
 	else if (info->severity == AER_FATAL)

include/linux/pci.h

@@ -843,6 +843,9 @@ struct pci_error_handlers {
 
 	/* Device driver may resume normal operations */
 	void (*resume)(struct pci_dev *dev);
+
+	/* Allow device driver to record more details of a correctable error */
+	void (*cor_error_detected)(struct pci_dev *dev);
 };