firmware: arm_ffa: Skip Rx buffer ownership release if not acquired

[ Upstream commit 4567bda ]

Completion of the FFA_PARTITION_INFO_GET ABI transfers the ownership of
the caller’s Rx buffer from the producer(typically partition mnager) to
the consumer(this driver/OS). FFA_RX_RELEASE transfers the ownership
from the consumer back to the producer.

However, when we set the flag to just return the count of partitions
deployed in the system corresponding to the specified UUID while
invoking FFA_PARTITION_INFO_GET, the Rx buffer ownership shouldn't be
transferred to this driver. We must be able to skip transferring back
the ownership to the partition manager when we request just to get the
count of the partitions as the buffers are not acquired in this case.

Firmware may return FFA_RET_DENIED or other error for the ffa_rx_release()
in such cases.

Fixes: bb1be74 ("firmware: arm_ffa: Add v1.1 get_partition_info support")
Message-Id: <20250321115700.3525197-1-sudeep.holla@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/firmware/arm_ffa/driver.c

@@ -280,7 +280,8 @@ __ffa_partition_info_get(u32 uuid0, u32 uuid1, u32 uuid2, u32 uuid3,
 			memcpy(buffer + idx, drv_info->rx_buffer + idx * sz,
 			       buf_sz);
 
-	ffa_rx_release();
+	if (!(flags & PARTITION_INFO_GET_RETURN_COUNT_ONLY))
+		ffa_rx_release();
 
 	mutex_unlock(&drv_info->rx_lock);