[PATCH v4 23/23] PCI/AER: Unmask RCEC internal errors to enable RCH downstream port error handling

[Terry Bowman <terry.bowman@amd.com>]

From: Robert Richter <rrichter@amd.com>

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 6.0, 7.8.4.3 Uncorrectable Error Mask Register,
    7.8.4.6 Correctable Error Mask Register

Co-developed-by: Terry Bowman <terry.bowman@amd.com>
Signed-off-by: Terry Bowman <terry.bowman@amd.com>
Signed-off-by: Robert Richter <rrichter@amd.com>
---
 drivers/pci/pcie/aer.c | 64 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
index 2e3f00b6a5bd..c5076ae4eb58 100644
--- a/drivers/pci/pcie/aer.c
+++ b/drivers/pci/pcie/aer.c
@@ -948,6 +948,32 @@ static bool find_source_device(struct pci_dev *parent,
 
 #ifdef CONFIG_PCIEAER_CXL
 
+static int pci_aer_unmask_internal_errors(struct pci_dev *dev)
+{
+	int aer, rc;
+	u32 mask;
+
+	if (!pcie_aer_is_native(dev))
+		return -EIO;
+
+	aer = dev->aer_cap;
+	rc = pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, &mask);
+	if (rc)
+		return rc;
+	mask &= ~PCI_ERR_UNC_INTN;
+	rc = pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, mask);
+	if (rc)
+		return rc;
+
+	rc = pci_read_config_dword(dev, aer + PCI_ERR_COR_MASK, &mask);
+	if (rc)
+		return rc;
+	mask &= ~PCI_ERR_COR_INTERNAL;
+	rc = pci_write_config_dword(dev, aer + PCI_ERR_COR_MASK, mask);
+
+	return rc;
+}
+
 static bool is_cxl_mem_dev(struct pci_dev *dev)
 {
 	/*
@@ -1031,7 +1057,44 @@ 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)
+{
+	int *handles_cxl = data;
+
+	*handles_cxl = is_cxl_mem_dev(dev) && cxl_error_is_native(dev);
+
+	return *handles_cxl;
+}
+
+static bool handles_cxl_errors(struct pci_dev *rcec)
+{
+	int handles_cxl = 0;
+
+	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;
+
+	/*
+	 * Internal errors are masked by default, unmask RCEC's here
+	 * PCI6.0 7.8.4.3 Uncorrectable Error Mask Register (Offset 08h)
+	 * PCI6.0 7.8.4.6 Correctable Error Mask Register (Offset 14h)
+	 */
+	if (pci_aer_unmask_internal_errors(rcec))
+		pci_err(rcec, "CXL: Failed to unmask internal errors");
+	else
+		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
@@ -1432,6 +1495,7 @@ 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;
-- 
2.34.1