linux-kernel - [PATCH v5 23/26] cxl/pci: Disable root port interrupts in RCH mode

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Date:   Wed, 7 Jun 2023 17:16:48 -0500
From:   Terry Bowman <terry.bowman@....com>
To:     <alison.schofield@...el.com>, <vishal.l.verma@...el.com>,
        <ira.weiny@...el.com>, <bwidawsk@...nel.org>,
        <dan.j.williams@...el.com>, <dave.jiang@...el.com>,
        <Jonathan.Cameron@...wei.com>, <linux-cxl@...r.kernel.org>
CC:     <terry.bowman@....com>, <rrichter@....com>,
        <linux-kernel@...r.kernel.org>, <bhelgaas@...gle.com>
Subject: [PATCH v5 23/26] 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@....com>
---
 drivers/cxl/core/port.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index bc5d0ee9da54..828ae69086c4 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -981,6 +981,30 @@ static int cxl_dport_map_regs(struct cxl_dport *dport)
 	return 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;
+	u32 aer_cmd_mask, aer_cmd;
+
+	if (!dport->rch || !aer_base)
+		return;
+
+	/*
+	 * Disable RCH root port command interrupts.
+	 * CXL 3.0 12.2.1.1 - RCH Downstream Port-detected Errors
+	 *
+	 * This sequnce 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.
+	 */
+	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);
+}
+
 static struct cxl_dport *
 __devm_cxl_add_dport(struct cxl_port *port, struct device *dport_dev,
 		     int port_id, resource_size_t component_reg_phys,
@@ -1038,6 +1062,8 @@ __devm_cxl_add_dport(struct cxl_port *port, struct device *dport_dev,
 	if (rc && rc != -ENODEV)
 		return ERR_PTR(rc);
 
+	cxl_disable_rch_root_ints(dport);
+
 	cond_cxl_root_lock(port);
 	rc = add_dport(port, dport);
 	cond_cxl_root_unlock(port);
-- 
2.34.1