linux-kernel - [PATCH V2 01/11] cxl/pci: Add generic MSI-X/MSI irq support

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Date:   Wed, 30 Nov 2022 16:27:09 -0800
From:   ira.weiny@...el.com
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Davidlohr Bueso <dave@...olabs.net>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Dave Jiang <dave.jiang@...el.com>,
        linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org
Subject: [PATCH V2 01/11] cxl/pci: Add generic MSI-X/MSI irq support

From: Davidlohr Bueso <dave@...olabs.net>

Currently the only CXL features targeted for irq support require their
message numbers to be within the first 16 entries.  The device may
however support less than 16 entries depending on the support it
provides.

Attempt to allocate these 16 irq vectors.  If the device supports less
then the PCI infrastructure will allocate that number.  Store the number
of vectors actually allocated in the device state for later use
by individual functions.

Upon successful allocation, users can plug in their respective isr at
any point thereafter, for example, if the irq setup is not done in the
PCI driver, such as the case of the CXL-PMU.

Cc: Bjorn Helgaas <helgaas@...nel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Co-developed-by: Ira Weiny <ira.weiny@...el.com>
Signed-off-by: Ira Weiny <ira.weiny@...el.com>
Signed-off-by: Davidlohr Bueso <dave@...olabs.net>

---
Changes from V1:
	Jonathan
		pci_alloc_irq_vectors() cleans up the vectors automatically
		use msi_enabled rather than nr_irq_vecs

Changes from Ira
	Remove reviews
	Allocate up to a static 16 vectors.
	Change cover letter
---
 drivers/cxl/cxlmem.h |  3 +++
 drivers/cxl/cxlpci.h |  6 ++++++
 drivers/cxl/pci.c    | 23 +++++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 88e3a8e54b6a..cd35f43fedd4 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -211,6 +211,7 @@ struct cxl_endpoint_dvsec_info {
  * @info: Cached DVSEC information about the device.
  * @serial: PCIe Device Serial Number
  * @doe_mbs: PCI DOE mailbox array
+ * @msi_enabled: MSI-X/MSI has been enabled
  * @mbox_send: @dev specific transport for transmitting mailbox commands
  *
  * See section 8.2.9.5.2 Capacity Configuration and Label Storage for
@@ -247,6 +248,8 @@ struct cxl_dev_state {
 
 	struct xarray doe_mbs;
 
+	bool msi_enabled;
+
 	int (*mbox_send)(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd);
 };
 
diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
index eec597dbe763..b7f4e2f417d3 100644
--- a/drivers/cxl/cxlpci.h
+++ b/drivers/cxl/cxlpci.h
@@ -53,6 +53,12 @@
 #define	    CXL_DVSEC_REG_LOCATOR_BLOCK_ID_MASK			GENMASK(15, 8)
 #define     CXL_DVSEC_REG_LOCATOR_BLOCK_OFF_LOW_MASK		GENMASK(31, 16)
 
+/*
+ * NOTE: Currently all the functions which are enabled for CXL require their
+ * vectors to be in the first 16.  Use this as the max.
+ */
+#define CXL_PCI_REQUIRED_VECTORS 16
+
 /* Register Block Identifier (RBI) */
 enum cxl_regloc_type {
 	CXL_REGLOC_RBI_EMPTY = 0,
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index faeb5d9d7a7a..8f86f85d89c7 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -428,6 +428,27 @@ static void devm_cxl_pci_create_doe(struct cxl_dev_state *cxlds)
 	}
 }
 
+static void cxl_pci_alloc_irq_vectors(struct cxl_dev_state *cxlds)
+{
+	struct device *dev = cxlds->dev;
+	struct pci_dev *pdev = to_pci_dev(dev);
+	int nvecs;
+
+	/*
+	 * NOTE: pci_alloc_irq_vectors() handles calling pci_free_irq_vectors()
+	 * automatically despite not being called pcim_*.  See
+	 * pci_setup_msi_context().
+	 */
+	nvecs = pci_alloc_irq_vectors(pdev, 1, CXL_PCI_REQUIRED_VECTORS,
+				   PCI_IRQ_MSIX | PCI_IRQ_MSI);
+	if (nvecs < 0) {
+		dev_dbg(dev, "Failed to alloc irq vectors; use polling instead.\n");
+		return;
+	}
+
+	cxlds->msi_enabled = true;
+}
+
 static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 {
 	struct cxl_register_map map;
@@ -494,6 +515,8 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (rc)
 		return rc;
 
+	cxl_pci_alloc_irq_vectors(cxlds);
+
 	cxlmd = devm_cxl_add_memdev(cxlds);
 	if (IS_ERR(cxlmd))
 		return PTR_ERR(cxlmd);
-- 
2.37.2