cxl/pci: Disable root port interrupts in RCH mode

The RCH root port contains root command AER registers that should not be
enabled.[1] Disable these to prevent root port interrupts.

[1] CXL 3.0 - 12.2.1.1 RCH Downstream Port-detected Errors
Signed-off-by: Terry Bowman <terry.bowman@amd.com>
Signed-off-by: Robert Richter <rrichter@amd.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20231018171713.1883517-17-rrichter@amd.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/pci.c

@@ -763,6 +763,35 @@ static void cxl_dport_map_regs(struct cxl_dport *dport)
 		cxl_dport_map_rch_aer(dport);
 }
 
+static void cxl_disable_rch_root_ints(struct cxl_dport *dport)
+{
+	void __iomem *aer_base = dport->regs.dport_aer;
+	struct pci_host_bridge *bridge;
+	u32 aer_cmd_mask, aer_cmd;
+
+	if (!aer_base)
+		return;
+
+	bridge = to_pci_host_bridge(dport->dport_dev);
+
+	/*
+	 * Disable RCH root port command interrupts.
+	 * CXL 3.0 12.2.1.1 - RCH Downstream Port-detected Errors
+	 *
+	 * This sequence may not be necessary. CXL spec states disabling
+	 * the root cmd register's interrupts is required. But, PCI spec
+	 * shows these are disabled by default on reset.
+	 */
+	if (bridge->native_cxl_error) {
+		aer_cmd_mask = (PCI_ERR_ROOT_CMD_COR_EN |
+				PCI_ERR_ROOT_CMD_NONFATAL_EN |
+				PCI_ERR_ROOT_CMD_FATAL_EN);
+		aer_cmd = readl(aer_base + PCI_ERR_ROOT_COMMAND);
+		aer_cmd &= ~aer_cmd_mask;
+		writel(aer_cmd, aer_base + PCI_ERR_ROOT_COMMAND);
+	}
+}
+
 void cxl_setup_parent_dport(struct device *host, struct cxl_dport *dport)
 {
 	struct device *dport_dev = dport->dport_dev;
@@ -774,6 +803,9 @@ void cxl_setup_parent_dport(struct device *host, struct cxl_dport *dport)
 
 	dport->reg_map.host = host;
 	cxl_dport_map_regs(dport);
+
+	if (dport->rch)
+		cxl_disable_rch_root_ints(dport);
 }
 EXPORT_SYMBOL_NS_GPL(cxl_setup_parent_dport, CXL);