[PATCH v12 18/20] PCI/AER: Unmask RCEC internal errors to enable RCH downstream port error handling

[Robert Richter]

AER corrected and uncorrectable internal errors (CIE/UIE) are masked
in their corresponding mask registers per default once in power-up
state. [1][2] Enable internal errors for RCECs to receive CXL
downstream port errors of Restricted CXL Hosts (RCHs).

[1] CXL 3.0 Spec, 12.2.1.1 - RCH Downstream Port Detected Errors
[2] PCIe Base Spec r6.0, 7.8.4.3 Uncorrectable Error Mask Register,
    7.8.4.6 Correctable Error Mask Register

Co-developed-by: Terry Bowman <terry.bow...@amd.com>
Signed-off-by: Terry Bowman <terry.bow...@amd.com>
Signed-off-by: Robert Richter <rrich...@amd.com>
Acked-by: Bjorn Helgaas <bhelg...@google.com>
Reviewed-by: Jonathan Cameron <jonathan.came...@huawei.com>
Reviewed-by: Dave Jiang <dave.ji...@intel.com>
---
 drivers/pci/pcie/aer.c | 57 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index f1e8494f5bb6..41076cb2956e 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -936,6 +936,30 @@ static bool find_source_device(struct pci_dev *parent,
 
 #ifdef CONFIG_PCIEAER_CXL
 
+/**
+ * pci_aer_unmask_internal_errors - unmask internal errors
+ * @dev: pointer to the pcie_dev data structure
+ *
+ * Unmasks internal errors in the Uncorrectable and Correctable Error
+ * Mask registers.
+ *
+ * Note: AER must be enabled and supported by the device which must be
+ * checked in advance, e.g. with pcie_aer_is_native().
+ */
+static void pci_aer_unmask_internal_errors(struct pci_dev *dev)
+{
+       int aer = dev->aer_cap;
+       u32 mask;
+
+       pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, &mask);
+       mask &= ~PCI_ERR_UNC_INTN;
+       pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, mask);
+
+       pci_read_config_dword(dev, aer + PCI_ERR_COR_MASK, &mask);
+       mask &= ~PCI_ERR_COR_INTERNAL;
+       pci_write_config_dword(dev, aer + PCI_ERR_COR_MASK, mask);
+}
+
 static bool is_cxl_mem_dev(struct pci_dev *dev)
 {
        /*
@@ -1012,7 +1036,39 @@ static void cxl_rch_handle_error(struct pci_dev *dev, 
struct aer_err_info *info)
                pcie_walk_rcec(dev, cxl_rch_handle_error_iter, info);
 }
 
+static int handles_cxl_error_iter(struct pci_dev *dev, void *data)
+{
+       bool *handles_cxl = data;
+
+       if (!*handles_cxl)
+               *handles_cxl = is_cxl_mem_dev(dev) && cxl_error_is_native(dev);
+
+       /* Non-zero terminates iteration */
+       return *handles_cxl;
+}
+
+static bool handles_cxl_errors(struct pci_dev *rcec)
+{
+       bool handles_cxl = false;
+
+       if (pci_pcie_type(rcec) == PCI_EXP_TYPE_RC_EC &&
+           pcie_aer_is_native(rcec))
+               pcie_walk_rcec(rcec, handles_cxl_error_iter, &handles_cxl);
+
+       return handles_cxl;
+}
+
+static void cxl_rch_enable_rcec(struct pci_dev *rcec)
+{
+       if (!handles_cxl_errors(rcec))
+               return;
+
+       pci_aer_unmask_internal_errors(rcec);
+       pci_info(rcec, "CXL: Internal errors unmasked");
+}
+
 #else
+static inline void cxl_rch_enable_rcec(struct pci_dev *dev) { }
 static inline void cxl_rch_handle_error(struct pci_dev *dev,
                                        struct aer_err_info *info) { }
 #endif
@@ -1412,6 +1468,7 @@ static int aer_probe(struct pcie_device *dev)
                return status;
        }
 
+       cxl_rch_enable_rcec(port);
        aer_enable_rootport(rpc);
        pci_info(port, "enabled with IRQ %d\n", dev->irq);
        return 0;
-- 
2.30.2