[PATCH v7 3/9] PCI: endpoint: Add auxiliary resource query API

[Koichiro Den]

Endpoint controller drivers may integrate auxiliary blocks (e.g. DMA
engines) whose register windows and descriptor memories metadata need to
be exposed to a remote peer. Endpoint function drivers need a generic
way to discover such resources without hard-coding controller-specific
helpers.

Add pci_epc_get_aux_resources() and the corresponding pci_epc_ops
get_aux_resources() callback. The API returns a list of resources
described by type, physical address and size, plus type-specific
metadata.

Passing resources == NULL (or num_resources == 0) returns the required
number of entries.

Signed-off-by: Koichiro Den <den at valinux.co.jp>
---
 drivers/pci/endpoint/pci-epc-core.c | 41 +++++++++++++++++++++++
 include/linux/pci-epc.h             | 51 +++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+)

diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 068155819c57..01de4bd5047a 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -155,6 +155,47 @@ const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
 }
 EXPORT_SYMBOL_GPL(pci_epc_get_features);
 
+/**
+ * pci_epc_get_aux_resources() - query EPC-provided auxiliary resources
+ * @epc: EPC device
+ * @func_no: function number
+ * @vfunc_no: virtual function number
+ * @resources: output array (may be NULL to query required count)
+ * @num_resources: size of @resources array in entries (0 when querying count)
+ *
+ * Some EPC backends integrate auxiliary blocks (e.g. DMA engines) whose control
+ * registers and/or descriptor memories can be exposed to the host by mapping
+ * them into BAR space. This helper queries the backend for such resources.
+ *
+ * Return:
+ *   * >= 0: number of resources returned (or required, if @resources is NULL)
+ *   * -EOPNOTSUPP: backend does not support auxiliary resource queries
+ *   * other -errno on failure
+ */
+int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			      struct pci_epc_aux_resource *resources,
+			      int num_resources)
+{
+	int ret;
+
+	if (!epc || !epc->ops)
+		return -EINVAL;
+
+	if (func_no >= epc->max_functions)
+		return -EINVAL;
+
+	if (!epc->ops->get_aux_resources)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&epc->lock);
+	ret = epc->ops->get_aux_resources(epc, func_no, vfunc_no, resources,
+					  num_resources);
+	mutex_unlock(&epc->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pci_epc_get_aux_resources);
+
 /**
  * pci_epc_stop() - stop the PCI link
  * @epc: the link of the EPC device that has to be stopped
diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index 7a87f5962dd0..fd79784b31db 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -61,6 +61,50 @@ struct pci_epc_map {
 	void __iomem	*virt_addr;
 };
 
+/**
+ * enum pci_epc_aux_resource_type - auxiliary resource type identifiers
+ * @PCI_EPC_AUX_DMA_CTRL_MMIO: Integrated DMA controller register window (MMIO)
+ * @PCI_EPC_AUX_DMA_CHAN_DESC: Per-channel DMA descriptor
+ * @PCI_EPC_AUX_DOORBELL_MMIO: Doorbell MMIO, that might be outside the DMA
+ *                             controller register window
+ *
+ * EPC backends may expose auxiliary blocks (e.g. DMA engines) by mapping their
+ * register windows and descriptor memories into BAR space. This enum
+ * identifies the type of each exposable resource.
+ */
+enum pci_epc_aux_resource_type {
+	PCI_EPC_AUX_DMA_CTRL_MMIO,
+	PCI_EPC_AUX_DMA_CHAN_DESC,
+	PCI_EPC_AUX_DOORBELL_MMIO,
+};
+
+/**
+ * struct pci_epc_aux_resource - a physical auxiliary resource that may be
+ *                               exposed for peer use
+ * @type:       resource type, see enum pci_epc_aux_resource_type
+ * @phys_addr:  physical base address of the resource
+ * @size:       size of the resource in bytes
+ * @bar:        BAR number where this resource is already exposed to the RC
+ *              (NO_BAR if not)
+ * @bar_offset: offset within @bar where the resource starts (valid iff
+ *              @bar != NO_BAR)
+ * @u:          type-specific metadata
+ */
+struct pci_epc_aux_resource {
+	enum pci_epc_aux_resource_type type;
+	phys_addr_t phys_addr;
+	resource_size_t size;
+	enum pci_barno bar;
+	resource_size_t bar_offset;
+
+	union {
+		/* PCI_EPC_AUX_DOORBELL_MMIO */
+		struct {
+			int irq;
+		} db_mmio;
+	} u;
+};
+
 /**
  * struct pci_epc_ops - set of function pointers for performing EPC operations
  * @write_header: ops to populate configuration space header
@@ -84,6 +128,7 @@ struct pci_epc_map {
  * @start: ops to start the PCI link
  * @stop: ops to stop the PCI link
  * @get_features: ops to get the features supported by the EPC
+ * @get_aux_resources: ops to retrieve controller-owned auxiliary resources
  * @owner: the module owner containing the ops
  */
 struct pci_epc_ops {
@@ -115,6 +160,9 @@ struct pci_epc_ops {
 	void	(*stop)(struct pci_epc *epc);
 	const struct pci_epc_features* (*get_features)(struct pci_epc *epc,
 						       u8 func_no, u8 vfunc_no);
+	int	(*get_aux_resources)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+				     struct pci_epc_aux_resource *resources,
+				     int num_resources);
 	struct module *owner;
 };
 
@@ -337,6 +385,9 @@ int pci_epc_start(struct pci_epc *epc);
 void pci_epc_stop(struct pci_epc *epc);
 const struct pci_epc_features *pci_epc_get_features(struct pci_epc *epc,
 						    u8 func_no, u8 vfunc_no);
+int pci_epc_get_aux_resources(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			      struct pci_epc_aux_resource *resources,
+			      int num_resources);
 enum pci_barno
 pci_epc_get_first_free_bar(const struct pci_epc_features *epc_features);
 enum pci_barno pci_epc_get_next_free_bar(const struct pci_epc_features
-- 
2.51.0