platform-msi: Allow creation of a MSI-based stacked irq domain

We almost have all the needed bits requiredable to create a irq domain
on top of a MSI domain.

For this, we enable a few things:
- the virq is stored in the msi_desc
- device, msi_alloc_info and domain-specific data
  are stored in the platform_priv_data structure
- we introduce a new API for platform-msi:

  /* Create a MSI-based domain */
  struct irq_domain *
  platform_msi_create_device_domain(struct device *dev,
                                    unsigned int nvec,
                                    irq_write_msi_msg_t write_msi_msg,
                                    const struct irq_domain_ops *ops,
                                    void *host_data);

  /* Allocate MSIs in an MSI domain */
  int platform_msi_domain_alloc(struct irq_domain *domain,
				unsigned int virq,
				unsigned int nr_irqs);

  /* Free MSIs from an MSI domain */
  void platform_msi_domain_free(struct irq_domain *domain,
				unsigned int virq,
				unsigned int nvec);

  /* Obtain the host data passed to platform_msi_create_device_domain */
  void *platform_msi_get_host_data(struct irq_domain *domain);

platform_msi_create_device_domain() is a hybrid of irqdomain creation
and interrupt allocation, creating a domain backed by the MSIs associated
to a device. IRQs can then be allocated in that domain using
platform_msi_domain_alloc().

This now allows a wired irq to MSI bridge to be created.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/base/platform-msi.c

@@ -32,6 +32,9 @@
  * and the callback to write the MSI message.
  */
 struct platform_msi_priv_data {
+	struct device		*dev;
+	void 			*host_data;
+	msi_alloc_info_t	arg;
 	irq_write_msi_msg_t	write_msg;
 	int			devid;
 };
@@ -124,8 +127,9 @@ static void platform_msi_free_descs(struct device *dev, int base, int nvec)
 	}
 }
 
-static int platform_msi_alloc_descs(struct device *dev, int nvec,
-				    struct platform_msi_priv_data *data)
+static int platform_msi_alloc_descs_with_irq(struct device *dev, int virq,
+					     int nvec,
+					     struct platform_msi_priv_data *data)
 
 {
 	struct msi_desc *desc;
@@ -145,6 +149,7 @@ static int platform_msi_alloc_descs(struct device *dev, int nvec,
 		desc->platform.msi_priv_data = data;
 		desc->platform.msi_index = base + i;
 		desc->nvec_used = 1;
+		desc->irq = virq ? virq + i : 0;
 
 		list_add_tail(&desc->list, dev_to_msi_list(dev));
 	}
@@ -159,6 +164,13 @@ static int platform_msi_alloc_descs(struct device *dev, int nvec,
 	return 0;
 }
 
+static int platform_msi_alloc_descs(struct device *dev, int nvec,
+				    struct platform_msi_priv_data *data)
+
+{
+	return platform_msi_alloc_descs_with_irq(dev, 0, nvec, data);
+}
+
 /**
  * platform_msi_create_irq_domain - Create a platform MSI interrupt domain
  * @fwnode:		Optional fwnode of the interrupt controller
@@ -225,6 +237,7 @@ platform_msi_alloc_priv_data(struct device *dev, unsigned int nvec,
 	}
 
 	datap->write_msg = write_msi_msg;
+	datap->dev = dev;
 
 	return datap;
 }
@@ -288,3 +301,116 @@ void platform_msi_domain_free_irqs(struct device *dev)
 	msi_domain_free_irqs(dev->msi_domain, dev);
 	platform_msi_free_descs(dev, 0, MAX_DEV_MSIS);
 }
+
+/**
+ * platform_msi_get_host_data - Query the private data associated with
+ *                              a platform-msi domain
+ * @domain:	The platform-msi domain
+ *
+ * Returns the private data provided when calling
+ * platform_msi_create_device_domain.
+ */
+void *platform_msi_get_host_data(struct irq_domain *domain)
+{
+	struct platform_msi_priv_data *data = domain->host_data;
+	return data->host_data;
+}
+
+/**
+ * platform_msi_create_device_domain - Create a platform-msi domain
+ *
+ * @dev:		The device generating the MSIs
+ * @nvec:		The number of MSIs that need to be allocated
+ * @write_msi_msg:	Callback to write an interrupt message for @dev
+ * @ops:		The hierarchy domain operations to use
+ * @host_data:		Private data associated to this domain
+ *
+ * Returns an irqdomain for @nvec interrupts
+ */
+struct irq_domain *
+platform_msi_create_device_domain(struct device *dev,
+				  unsigned int nvec,
+				  irq_write_msi_msg_t write_msi_msg,
+				  const struct irq_domain_ops *ops,
+				  void *host_data)
+{
+	struct platform_msi_priv_data *data;
+	struct irq_domain *domain;
+	int err;
+
+	data = platform_msi_alloc_priv_data(dev, nvec, write_msi_msg);
+	if (IS_ERR(data))
+		return NULL;
+
+	data->host_data = host_data;
+	domain = irq_domain_create_hierarchy(dev->msi_domain, 0, nvec,
+					     of_node_to_fwnode(dev->of_node),
+					     ops, data);
+	if (!domain)
+		goto free_priv;
+
+	err = msi_domain_prepare_irqs(domain->parent, dev, nvec, &data->arg);
+	if (err)
+		goto free_domain;
+
+	return domain;
+
+free_domain:
+	irq_domain_remove(domain);
+free_priv:
+	platform_msi_free_priv_data(data);
+	return NULL;
+}
+
+/**
+ * platform_msi_domain_free - Free interrupts associated with a platform-msi
+ *                            domain
+ *
+ * @domain:	The platform-msi domain
+ * @virq:	The base irq from which to perform the free operation
+ * @nvec:	How many interrupts to free from @virq
+ */
+void platform_msi_domain_free(struct irq_domain *domain, unsigned int virq,
+			      unsigned int nvec)
+{
+	struct platform_msi_priv_data *data = domain->host_data;
+	struct msi_desc *desc;
+	for_each_msi_entry(desc, data->dev) {
+		if (WARN_ON(!desc->irq || desc->nvec_used != 1))
+			return;
+		if (!(desc->irq >= virq && desc->irq < (virq + nvec)))
+			continue;
+
+		irq_domain_free_irqs_common(domain, desc->irq, 1);
+	}
+}
+
+/**
+ * platform_msi_domain_alloc - Allocate interrupts associated with
+ *			       a platform-msi domain
+ *
+ * @domain:	The platform-msi domain
+ * @virq:	The base irq from which to perform the allocate operation
+ * @nvec:	How many interrupts to free from @virq
+ *
+ * Return 0 on success, or an error code on failure. Must be called
+ * with irq_domain_mutex held (which can only be done as part of a
+ * top-level interrupt allocation).
+ */
+int platform_msi_domain_alloc(struct irq_domain *domain, unsigned int virq,
+			      unsigned int nr_irqs)
+{
+	struct platform_msi_priv_data *data = domain->host_data;
+	int err;
+
+	err = platform_msi_alloc_descs_with_irq(data->dev, virq, nr_irqs, data);
+	if (err)
+		return err;
+
+	err = msi_domain_populate_irqs(domain->parent, data->dev,
+				       virq, nr_irqs, &data->arg);
+	if (err)
+		platform_msi_domain_free(domain, virq, nr_irqs);
+
+	return err;
+}

include/linux/msi.h

@@ -174,6 +174,7 @@ struct msi_controller {
 #include <asm/msi.h>
 
 struct irq_domain;
+struct irq_domain_ops;
 struct irq_chip;
 struct device_node;
 struct fwnode_handle;
@@ -285,6 +286,17 @@ int msi_domain_prepare_irqs(struct irq_domain *domain, struct device *dev,
 			    int nvec, msi_alloc_info_t *args);
 int msi_domain_populate_irqs(struct irq_domain *domain, struct device *dev,
 			     int virq, int nvec, msi_alloc_info_t *args);
+struct irq_domain *
+platform_msi_create_device_domain(struct device *dev,
+				  unsigned int nvec,
+				  irq_write_msi_msg_t write_msi_msg,
+				  const struct irq_domain_ops *ops,
+				  void *host_data);
+int platform_msi_domain_alloc(struct irq_domain *domain, unsigned int virq,
+			      unsigned int nr_irqs);
+void platform_msi_domain_free(struct irq_domain *domain, unsigned int virq,
+			      unsigned int nvec);
+void *platform_msi_get_host_data(struct irq_domain *domain);
 #endif /* CONFIG_GENERIC_MSI_IRQ_DOMAIN */
 
 #ifdef CONFIG_PCI_MSI_IRQ_DOMAIN