1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/mailbox/mtk-cmdq-mailbox.h b/include/linux/mailbox/mtk-cmdq-mailbox.h
index 4c1a91b07de3..e1555e06e7e5 100644
--- a/include/linux/mailbox/mtk-cmdq-mailbox.h
+++ b/include/linux/mailbox/mtk-cmdq-mailbox.h
@@ -77,6 +77,16 @@ struct cmdq_pkt {
 	size_t			buf_size; /* real buffer size */
 };
 
+/**
+ * cmdq_get_shift_pa() - get the shift bits of physical address
+ * @chan: mailbox channel
+ *
+ * GCE can only fetch the command buffer address from a 32-bit register.
+ * Some SOCs support more than 32-bit command buffer address for GCE, which
+ * requires some shift bits to make the address fit into the 32-bit register.
+ *
+ * Return: the shift bits of physical address
+ */
 u8 cmdq_get_shift_pa(struct mbox_chan *chan);
 
 #endif /* __MTK_CMDQ_MAILBOX_H__ */