[PATCH v2] firmware: arm_ffa: Add support for FFA_MSG_SEND2

[Sudeep Holla]

The FFA_MSG_SEND2 can be  used to transmit a partition message from
the Tx buffer of the sender(the driver in this case) endpoint to the Rx
buffer of the receiver endpoint.

An invocation of the FFA_MSG_SEND2 transfers the ownership of the Tx
buffer to the receiver endpoint(or any intermediate consumer). Completion
of an FFA_MSG_SEND2 invocation transfers the ownership of the buffer
back to the sender endpoint.

The framework defines the FFA_MSG_SEND2 interface to transmit a partition
message from the Tx buffer of the sender to the Rx buffer of a receiver
and inform the scheduler that the receiver must be run.

Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
---
 drivers/firmware/arm_ffa/driver.c | 38 +++++++++++++++++++++++++++++++
 include/linux/arm_ffa.h           |  9 ++++++++
 2 files changed, 47 insertions(+)

Changes in v2:
 - Made this independent/standalone patch
 - Fixed missing mutex_unlock() and incorrect use of mutex_lock() instead of
   mutex_unlock()
 - Add check for the max size of the message that can be supported
 - Link to v1: https://lore.kernel.org/linux-arm-kernel/20240415-ffa_msg2_support-v1-4-a28c964b1b3f@arm.com/

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index 7dfc20186496..3f1e8a280464 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -344,6 +344,38 @@ static int ffa_msg_send_direct_req(u16 src_id, u16 dst_id, bool mode_32bit,
 	return -EINVAL;
 }
 
+static int ffa_msg_send2(u16 src_id, u16 dst_id, void *buf, size_t sz)
+{
+	u32 src_dst_ids = PACK_TARGET_INFO(src_id, dst_id);
+	struct ffa_indirect_msg_hdr *msg;
+	ffa_value_t ret;
+	int retval = 0;
+
+	if (sz > (RXTX_BUFFER_SIZE - sizeof(*msg)))
+		return -ERANGE;
+
+	mutex_lock(&drv_info->tx_lock);
+
+	msg = drv_info->tx_buffer;
+	msg->flags = 0;
+	msg->res0 = 0;
+	msg->offset = sizeof(*msg);
+	msg->send_recv_id = src_dst_ids;
+	msg->size = sz;
+	memcpy(msg + msg->offset, buf, sz);
+
+	/* flags = 0, sender VMID = 0 works for both physical/virtual NS */
+	invoke_ffa_fn((ffa_value_t){
+		      .a0 = FFA_MSG_SEND2, .a1 = 0, .a2 = 0
+		      }, &ret);
+
+	if (ret.a0 == FFA_ERROR)
+		retval = ffa_to_linux_errno((int)ret.a2);
+
+	mutex_unlock(&drv_info->tx_lock);
+	return retval;
+}
+
 static int ffa_mem_first_frag(u32 func_id, phys_addr_t buf, u32 buf_sz,
 			      u32 frag_len, u32 len, u64 *handle)
 {
@@ -870,6 +902,11 @@ static int ffa_sync_send_receive(struct ffa_device *dev,
 				       dev->mode_32bit, data);
 }
 
+static int ffa_indirect_msg_send(struct ffa_device *dev, void *buf, size_t sz)
+{
+	return ffa_msg_send2(drv_info->vm_id, dev->vm_id, buf, sz);
+}
+
 static int ffa_memory_share(struct ffa_mem_ops_args *args)
 {
 	if (drv_info->mem_ops_native)
@@ -1145,6 +1182,7 @@ static const struct ffa_info_ops ffa_drv_info_ops = {
 static const struct ffa_msg_ops ffa_drv_msg_ops = {
 	.mode_32bit_set = ffa_mode_32bit_set,
 	.sync_send_receive = ffa_sync_send_receive,
+	.indirect_send = ffa_indirect_msg_send,
 };
 
 static const struct ffa_mem_ops ffa_drv_mem_ops = {
diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
index b8f10a0a89fa..92fcf8b9fc82 100644
--- a/include/linux/arm_ffa.h
+++ b/include/linux/arm_ffa.h
@@ -253,6 +253,14 @@ struct ffa_send_direct_data {
 	unsigned long data4; /* w7/x7 */
 };
 
+struct ffa_indirect_msg_hdr {
+	u32 flags;
+	u32 res0;
+	u32 offset;
+	u32 send_recv_id;
+	u32 size;
+};
+
 struct ffa_mem_region_addr_range {
 	/* The base IPA of the constituent memory region, aligned to 4 kiB */
 	u64 address;
@@ -413,6 +421,7 @@ struct ffa_msg_ops {
 	void (*mode_32bit_set)(struct ffa_device *dev);
 	int (*sync_send_receive)(struct ffa_device *dev,
 				 struct ffa_send_direct_data *data);
+	int (*indirect_send)(struct ffa_device *dev, void *buf, size_t sz);
 };
 
 struct ffa_mem_ops {
-- 
2.43.2