[PATCH v8 6/9] PCI: endpoint: pci-ep-msi: Refactor doorbell allocation for new backends

[Koichiro Den]

Prepare pci-ep-msi for non-MSI doorbell backends.

Factor MSI doorbell allocation into a helper and extend struct
pci_epf_doorbell_msg with:

  - irq_flags: required IRQ request flags (e.g. IRQF_SHARED for some
    backends)
  - type: doorbell backend type
  - bar/offset: pre-exposed doorbell target location, if any

Initialize these fields for the existing MSI-backed doorbell
implementation.

Also add PCI_EPF_DOORBELL_EMBEDDED type, which is to be implemented in a
follow-up patch.

No functional changes.

Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
Changes since v7:
  - Switch to designated initializer and rely on implicit
    zero-initialization.

 drivers/pci/endpoint/pci-ep-msi.c | 54 ++++++++++++++++++++++---------
 include/linux/pci-epf.h           | 23 +++++++++++--
 2 files changed, 60 insertions(+), 17 deletions(-)

diff --git a/drivers/pci/endpoint/pci-ep-msi.c b/drivers/pci/endpoint/pci-ep-msi.c
index ad8a81d6ad77..50badffa9d72 100644
--- a/drivers/pci/endpoint/pci-ep-msi.c
+++ b/drivers/pci/endpoint/pci-ep-msi.c
@@ -8,6 +8,7 @@
 
 #include <linux/device.h>
 #include <linux/export.h>
+#include <linux/interrupt.h>
 #include <linux/irqdomain.h>
 #include <linux/module.h>
 #include <linux/msi.h>
@@ -35,23 +36,13 @@ static void pci_epf_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
 	pci_epc_put(epc);
 }
 
-int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
+static int pci_epf_alloc_doorbell_msi(struct pci_epf *epf, u16 num_db)
 {
-	struct pci_epc *epc = epf->epc;
+	struct pci_epf_doorbell_msg *msg;
 	struct device *dev = &epf->dev;
+	struct pci_epc *epc = epf->epc;
 	struct irq_domain *domain;
-	void *msg;
-	int ret;
-	int i;
-
-	/* TODO: Multi-EPF support */
-	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
-		dev_err(dev, "MSI doorbell doesn't support multiple EPF\n");
-		return -EINVAL;
-	}
-
-	if (epf->db_msg)
-		return -EBUSY;
+	int ret, i;
 
 	domain = of_msi_map_get_device_domain(epc->dev.parent, 0,
 					      DOMAIN_BUS_PLATFORM_MSI);
@@ -74,6 +65,12 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
 	if (!msg)
 		return -ENOMEM;
 
+	for (i = 0; i < num_db; i++)
+		msg[i] = (struct pci_epf_doorbell_msg) {
+			.type = PCI_EPF_DOORBELL_MSI,
+			.bar = NO_BAR,
+		};
+
 	epf->num_db = num_db;
 	epf->db_msg = msg;
 
@@ -90,13 +87,40 @@ int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
 	for (i = 0; i < num_db; i++)
 		epf->db_msg[i].virq = msi_get_virq(epc->dev.parent, i);
 
+	return 0;
+}
+
+int pci_epf_alloc_doorbell(struct pci_epf *epf, u16 num_db)
+{
+	struct pci_epc *epc = epf->epc;
+	struct device *dev = &epf->dev;
+	int ret;
+
+	/* TODO: Multi-EPF support */
+	if (list_first_entry_or_null(&epc->pci_epf, struct pci_epf, list) != epf) {
+		dev_err(dev, "Doorbell doesn't support multiple EPF\n");
+		return -EINVAL;
+	}
+
+	if (epf->db_msg)
+		return -EBUSY;
+
+	ret = pci_epf_alloc_doorbell_msi(epf, num_db);
+	if (!ret)
+		return 0;
+
+	dev_err(dev, "Failed to allocate doorbell: %d\n", ret);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(pci_epf_alloc_doorbell);
 
 void pci_epf_free_doorbell(struct pci_epf *epf)
 {
-	platform_device_msi_free_irqs_all(epf->epc->dev.parent);
+	if (!epf->db_msg)
+		return;
+
+	if (epf->db_msg[0].type == PCI_EPF_DOORBELL_MSI)
+		platform_device_msi_free_irqs_all(epf->epc->dev.parent);
 
 	kfree(epf->db_msg);
 	epf->db_msg = NULL;
diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
index 7737a7c03260..cd747447a1ea 100644
--- a/include/linux/pci-epf.h
+++ b/include/linux/pci-epf.h
@@ -152,14 +152,33 @@ struct pci_epf_bar {
 	struct pci_epf_bar_submap	*submap;
 };
 
+enum pci_epf_doorbell_type {
+	PCI_EPF_DOORBELL_MSI = 0,
+	PCI_EPF_DOORBELL_EMBEDDED,
+};
+
 /**
  * struct pci_epf_doorbell_msg - represents doorbell message
- * @msg: MSI message
- * @virq: IRQ number of this doorbell MSI message
+ * @msg: Doorbell address/data pair to be mapped into BAR space.
+ *       For MSI-backed doorbells this is the MSI message, while for
+ *       "embedded" doorbells this represents an MMIO write that asserts
+ *       an interrupt on the EP side.
+ * @virq: IRQ number of this doorbell message
+ * @irq_flags: Required flags for request_irq()/request_threaded_irq().
+ *             Callers may OR-in additional flags (e.g. IRQF_ONESHOT).
+ * @type: Doorbell type.
+ * @bar: BAR number where the doorbell target is already exposed to the RC
+ *       (NO_BAR if not)
+ * @offset: offset within @bar for the doorbell target (valid iff
+ *          @bar != NO_BAR)
  */
 struct pci_epf_doorbell_msg {
 	struct msi_msg msg;
 	int virq;
+	unsigned long irq_flags;
+	enum pci_epf_doorbell_type type;
+	enum pci_barno bar;
+	resource_size_t offset;
 };
 
 /**
-- 
2.51.0