[U-Boot] [PATCH v4] arm: socfpga: mailbox: Fix off-by-one error on command length checking

[Ley Foon Tan]

A mailbox command contains 1-u32 header + arguments. The "len" variable
only contains the length of the arguments, but not the 1-u32 header.
Include the length of header when checking the ring buffer space to
prevent off-by-one error.

Signed-off-by: Ley Foon Tan <ley.foon.tan at intel.com>
Signed-off-by: Chee Hong Ang <chee.hong.ang at intel.com>
---
v3->v4:
- Change DWORD to u32 in commit message
- Add note len is in u32 unit in code

v2->v3:
- Update commit description.
---
 arch/arm/mach-socfpga/mailbox_s10.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-socfpga/mailbox_s10.c b/arch/arm/mach-socfpga/mailbox_s10.c
index 3c33223936..4498ab55df 100644
--- a/arch/arm/mach-socfpga/mailbox_s10.c
+++ b/arch/arm/mach-socfpga/mailbox_s10.c
@@ -55,11 +55,11 @@ static __always_inline int mbox_fill_cmd_circular_buff(u32 header, u32 len,
 	cout = MBOX_READL(MBOX_COUT) % MBOX_CMD_BUFFER_SIZE;
 
 	/* if command buffer is full or not enough free space
-	 * to fit the data
+	 * to fit the data. Note, len is in u32 unit.
 	 */
 	if (((cin + 1) % MBOX_CMD_BUFFER_SIZE) == cout ||
 	    ((MBOX_CMD_BUFFER_SIZE - cin + cout - 1) %
-	     MBOX_CMD_BUFFER_SIZE) < len)
+	     MBOX_CMD_BUFFER_SIZE) < (len + 1))
 		return -ENOMEM;
 
 	/* write header to circular buffer */
-- 
2.19.0