linux-kernel - [PATCH 2/2] cxl/mbox: Wire up basic irq support

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Date:   Fri, 14 Oct 2022 12:49:30 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     dan.j.williams@...el.com
Cc:     ira.weiny@...el.com, Jonathan.Cameron@...wei.com,
        dave.jiang@...el.com, alison.schofield@...el.com,
        vishal.l.verma@...el.com, bwidawsk@...nel.org,
        a.manzanares@...sung.com, linux-kernel@...r.kernel.org,
        linux-cxl@...r.kernel.org, dave@...olabs.net
Subject: [PATCH 2/2] cxl/mbox: Wire up basic irq support

This adds support for mailbox interrupts, which are needed, for
example, for background completion handling.

Signed-off-by: Davidlohr Bueso <dave@...olabs.net>
---
Note: We could also handle doorbell irq, but not sure this is
actually needed.

 drivers/cxl/cxl.h |  1 +
 drivers/cxl/pci.c | 27 ++++++++++++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 879661702054..d15a743bfc9e 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -140,6 +140,7 @@ enum {
 /* CXL 2.0 8.2.8.4 Mailbox Registers */
 #define CXLDEV_MBOX_CAPS_OFFSET 0x00
 #define   CXLDEV_MBOX_CAP_PAYLOAD_SIZE_MASK GENMASK(4, 0)
+#define   CXLDEV_MBOX_CAP_IRQ_MSGNUM_MASK GENMASK(10, 7)
 #define CXLDEV_MBOX_CTRL_OFFSET 0x04
 #define   CXLDEV_MBOX_CTRL_DOORBELL BIT(0)
 #define CXLDEV_MBOX_CMD_OFFSET 0x08
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index 942c4449d30f..6e18ca3e551f 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -51,6 +51,20 @@ static unsigned short mbox_ready_timeout = 60;
 module_param(mbox_ready_timeout, ushort, 0644);
 MODULE_PARM_DESC(mbox_ready_timeout, "seconds to wait for mailbox ready");
 
+static int cxl_pci_mbox_get_max_msgnum(struct cxl_dev_state *cxlds)
+{
+	int cap;
+
+	cap = readl(cxlds->regs.mbox + CXLDEV_MBOX_CAPS_OFFSET);
+	return FIELD_GET(CXLDEV_MBOX_CAP_IRQ_MSGNUM_MASK, cap);
+}
+
+static irqreturn_t cxl_pci_mbox_irq(int irq, void *id)
+{
+	/* TODO: handle completion of background commands */
+	return IRQ_HANDLED;
+}
+
 static int cxl_pci_mbox_wait_for_doorbell(struct cxl_dev_state *cxlds)
 {
 	const unsigned long start = jiffies;
@@ -271,6 +285,15 @@ static int cxl_pci_setup_mailbox(struct cxl_dev_state *cxlds)
 	dev_dbg(cxlds->dev, "Mailbox payload sized %zu",
 		cxlds->payload_size);
 
+	if (cxlds->irq_type == CXL_IRQ_MSI) {
+		struct device *dev = cxlds->dev;
+		int irq = cxl_pci_mbox_get_max_msgnum(cxlds);
+
+		if (devm_request_irq(dev, irq, cxl_pci_mbox_irq,
+				     IRQF_SHARED, "mailbox", cxlds))
+			dev_dbg(dev, "Mailbox irq (%d) supported", irq);
+	}
+
 	return 0;
 }
 
@@ -441,7 +464,9 @@ struct cxl_irq_cap {
 	int (*get_max_msgnum)(struct cxl_dev_state *cxlds);
 };
 
-static const struct cxl_irq_cap cxl_irq_cap_table[] = { NULL };
+static const struct cxl_irq_cap cxl_irq_cap_table[] = {
+	{ "mailbox", cxl_pci_mbox_get_max_msgnum }
+};
 
 static void cxl_pci_free_irq_vectors(void *data)
 {
-- 
2.37.3