[PATCH v3 16/28] cxl/mbox: Introduce the mbox_send operation

[Dan Williams <dan.j.williams@intel.com>]

In preparation for implementing a unit test backend transport for ioctl
operations, and making the mailbox available to the cxl/pmem
infrastructure, move the existing PCI specific portion of mailbox handling
to an "mbox_send" operation.

With this split all the PCI-specific transport details are comprehended
by a single operation and the rest of the mailbox infrastructure is
'struct cxl_mem' and 'struct cxl_memdev' generic.

Acked-by: Ben Widawsky <ben.widawsky@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/cxlmem.h |   42 ++++++++++++++++++++++++++++
 drivers/cxl/pci.c    |   76 ++++++++++++++------------------------------------
 2 files changed, 63 insertions(+), 55 deletions(-)

diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index 8397daea9d9b..a56d8f26a157 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -66,6 +66,45 @@ struct cxl_memdev *
 devm_cxl_add_memdev(struct device *host, struct cxl_mem *cxlm,
 		    const struct cdevm_file_operations *cdevm_fops);
 
+/**
+ * struct mbox_cmd - A command to be submitted to hardware.
+ * @opcode: (input) The command set and command submitted to hardware.
+ * @payload_in: (input) Pointer to the input payload.
+ * @payload_out: (output) Pointer to the output payload. Must be allocated by
+ *		 the caller.
+ * @size_in: (input) Number of bytes to load from @payload_in.
+ * @size_out: (input) Max number of bytes loaded into @payload_out.
+ *            (output) Number of bytes generated by the device. For fixed size
+ *            outputs commands this is always expected to be deterministic. For
+ *            variable sized output commands, it tells the exact number of bytes
+ *            written.
+ * @return_code: (output) Error code returned from hardware.
+ *
+ * This is the primary mechanism used to send commands to the hardware.
+ * All the fields except @payload_* correspond exactly to the fields described in
+ * Command Register section of the CXL 2.0 8.2.8.4.5. @payload_in and
+ * @payload_out are written to, and read from the Command Payload Registers
+ * defined in CXL 2.0 8.2.8.4.8.
+ */
+struct cxl_mbox_cmd {
+	u16 opcode;
+	void *payload_in;
+	void *payload_out;
+	size_t size_in;
+	size_t size_out;
+	u16 return_code;
+#define CXL_MBOX_SUCCESS 0
+};
+
+/*
+ * CXL 2.0 - Memory capacity multiplier
+ * See Section 8.2.9.5
+ *
+ * Volatile, Persistent, and Partition capacities are specified to be in
+ * multiples of 256MB - define a multiplier to convert to/from bytes.
+ */
+#define CXL_CAPACITY_MULTIPLIER SZ_256M
+
 /**
  * struct cxl_mem - A CXL memory device
  * @dev: The device associated with this CXL device.
@@ -80,6 +119,7 @@ devm_cxl_add_memdev(struct device *host, struct cxl_mem *cxlm,
  * @enabled_cmds: Hardware commands found enabled in CEL.
  * @pmem_range: Persistent memory capacity information.
  * @ram_range: Volatile memory capacity information.
+ * @mbox_send: @dev specific transport for transmitting mailbox commands
  */
 struct cxl_mem {
 	struct device *dev;
@@ -104,5 +144,7 @@ struct cxl_mem {
 	u64 active_persistent_bytes;
 	u64 next_volatile_bytes;
 	u64 next_persistent_bytes;
+
+	int (*mbox_send)(struct cxl_mem *cxlm, struct cxl_mbox_cmd *cmd);
 };
 #endif /* __CXL_MEM_H__ */
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index 24d84b69227a..a211b35af4be 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -64,45 +64,6 @@ enum opcode {
 	CXL_MBOX_OP_MAX			= 0x10000
 };
 
-/*
- * CXL 2.0 - Memory capacity multiplier
- * See Section 8.2.9.5
- *
- * Volatile, Persistent, and Partition capacities are specified to be in
- * multiples of 256MB - define a multiplier to convert to/from bytes.
- */
-#define CXL_CAPACITY_MULTIPLIER SZ_256M
-
-/**
- * struct mbox_cmd - A command to be submitted to hardware.
- * @opcode: (input) The command set and command submitted to hardware.
- * @payload_in: (input) Pointer to the input payload.
- * @payload_out: (output) Pointer to the output payload. Must be allocated by
- *		 the caller.
- * @size_in: (input) Number of bytes to load from @payload_in.
- * @size_out: (input) Max number of bytes loaded into @payload_out.
- *            (output) Number of bytes generated by the device. For fixed size
- *            outputs commands this is always expected to be deterministic. For
- *            variable sized output commands, it tells the exact number of bytes
- *            written.
- * @return_code: (output) Error code returned from hardware.
- *
- * This is the primary mechanism used to send commands to the hardware.
- * All the fields except @payload_* correspond exactly to the fields described in
- * Command Register section of the CXL 2.0 8.2.8.4.5. @payload_in and
- * @payload_out are written to, and read from the Command Payload Registers
- * defined in CXL 2.0 8.2.8.4.8.
- */
-struct mbox_cmd {
-	u16 opcode;
-	void *payload_in;
-	void *payload_out;
-	size_t size_in;
-	size_t size_out;
-	u16 return_code;
-#define CXL_MBOX_SUCCESS 0
-};
-
 static DECLARE_RWSEM(cxl_memdev_rwsem);
 static struct dentry *cxl_debugfs;
 static bool cxl_raw_allow_all;
@@ -266,7 +227,7 @@ static bool cxl_is_security_command(u16 opcode)
 }
 
 static void cxl_mem_mbox_timeout(struct cxl_mem *cxlm,
-				 struct mbox_cmd *mbox_cmd)
+				 struct cxl_mbox_cmd *mbox_cmd)
 {
 	struct device *dev = cxlm->dev;
 
@@ -297,7 +258,7 @@ static void cxl_mem_mbox_timeout(struct cxl_mem *cxlm,
  * mailbox.
  */
 static int __cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm,
-				   struct mbox_cmd *mbox_cmd)
+				   struct cxl_mbox_cmd *mbox_cmd)
 {
 	void __iomem *payload = cxlm->regs.mbox + CXLDEV_MBOX_PAYLOAD_OFFSET;
 	struct device *dev = cxlm->dev;
@@ -472,6 +433,20 @@ static void cxl_mem_mbox_put(struct cxl_mem *cxlm)
 	mutex_unlock(&cxlm->mbox_mutex);
 }
 
+static int cxl_pci_mbox_send(struct cxl_mem *cxlm, struct cxl_mbox_cmd *cmd)
+{
+	int rc;
+
+	rc = cxl_mem_mbox_get(cxlm);
+	if (rc)
+		return rc;
+
+	rc = __cxl_mem_mbox_send_cmd(cxlm, cmd);
+	cxl_mem_mbox_put(cxlm);
+
+	return rc;
+}
+
 /**
  * handle_mailbox_cmd_from_user() - Dispatch a mailbox command for userspace.
  * @cxlm: The CXL memory device to communicate with.
@@ -503,7 +478,7 @@ static int handle_mailbox_cmd_from_user(struct cxl_mem *cxlm,
 					s32 *size_out, u32 *retval)
 {
 	struct device *dev = cxlm->dev;
-	struct mbox_cmd mbox_cmd = {
+	struct cxl_mbox_cmd mbox_cmd = {
 		.opcode = cmd->opcode,
 		.size_in = cmd->info.size_in,
 		.size_out = cmd->info.size_out,
@@ -525,10 +500,6 @@ static int handle_mailbox_cmd_from_user(struct cxl_mem *cxlm,
 		}
 	}
 
-	rc = cxl_mem_mbox_get(cxlm);
-	if (rc)
-		goto out;
-
 	dev_dbg(dev,
 		"Submitting %s command for user\n"
 		"\topcode: %x\n"
@@ -539,8 +510,7 @@ static int handle_mailbox_cmd_from_user(struct cxl_mem *cxlm,
 	dev_WARN_ONCE(dev, cmd->info.id == CXL_MEM_COMMAND_ID_RAW,
 		      "raw command path used\n");
 
-	rc = __cxl_mem_mbox_send_cmd(cxlm, &mbox_cmd);
-	cxl_mem_mbox_put(cxlm);
+	rc = cxlm->mbox_send(cxlm, &mbox_cmd);
 	if (rc)
 		goto out;
 
@@ -874,7 +844,7 @@ static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, u16 opcode,
 				 void *out, size_t out_size)
 {
 	const struct cxl_mem_command *cmd = cxl_mem_find_command(opcode);
-	struct mbox_cmd mbox_cmd = {
+	struct cxl_mbox_cmd mbox_cmd = {
 		.opcode = opcode,
 		.payload_in = in,
 		.size_in = in_size,
@@ -886,12 +856,7 @@ static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, u16 opcode,
 	if (out_size > cxlm->payload_size)
 		return -E2BIG;
 
-	rc = cxl_mem_mbox_get(cxlm);
-	if (rc)
-		return rc;
-
-	rc = __cxl_mem_mbox_send_cmd(cxlm, &mbox_cmd);
-	cxl_mem_mbox_put(cxlm);
+	rc = cxlm->mbox_send(cxlm, &mbox_cmd);
 	if (rc)
 		return rc;
 
@@ -913,6 +878,7 @@ static int cxl_mem_setup_mailbox(struct cxl_mem *cxlm)
 {
 	const int cap = readl(cxlm->regs.mbox + CXLDEV_MBOX_CAPS_OFFSET);
 
+	cxlm->mbox_send = cxl_pci_mbox_send;
 	cxlm->payload_size =
 		1 << FIELD_GET(CXLDEV_MBOX_CAP_PAYLOAD_SIZE_MASK, cap);