[PATCH net-next 1/2] r8152: adjust generic_ocp_write function

[Hayes Wang <hayeswang@realtek.com>]

Reduce the control transfer if all bytes of first or the last DWORD are
writed.

The original method is to split the control transfer into three parts
(the first DWORD, middle continuous data, and the last DWORD). However,
they could be combined if whole bytes of the first DWORD or last DWORD
are writed. That is, the first DWORD or the last DWORD could be combined
with the middle continuous data, if the byte_en is 0xff.

Signed-off-by: Hayes Wang <hayeswang@realtek.com>
---
 drivers/net/usb/r8152.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 0738baa5b82e..f6578a99dbac 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -1314,16 +1314,24 @@ static int generic_ocp_write(struct r8152 *tp, u16 index, u16 byteen,
 	byteen_end = byteen & BYTE_EN_END_MASK;
 
 	byen = byteen_start | (byteen_start << 4);
-	ret = set_registers(tp, index, type | byen, 4, data);
-	if (ret < 0)
-		goto error1;
 
-	index += 4;
-	data += 4;
-	size -= 4;
+	/* Split the first DWORD if the byte_en is not 0xff */
+	if (byen != BYTE_EN_DWORD) {
+		ret = set_registers(tp, index, type | byen, 4, data);
+		if (ret < 0)
+			goto error1;
 
-	if (size) {
+		index += 4;
+		data += 4;
 		size -= 4;
+	}
+
+	if (size) {
+		byen = byteen_end | (byteen_end >> 4);
+
+		/* Split the last DWORD if the byte_en is not 0xff */
+		if (byen != BYTE_EN_DWORD)
+			size -= 4;
 
 		while (size) {
 			if (size > limit) {
@@ -1350,10 +1358,9 @@ static int generic_ocp_write(struct r8152 *tp, u16 index, u16 byteen,
 			}
 		}
 
-		byen = byteen_end | (byteen_end >> 4);
-		ret = set_registers(tp, index, type | byen, 4, data);
-		if (ret < 0)
-			goto error1;
+		/* Set the last DWORD */
+		if (byen != BYTE_EN_DWORD)
+			ret = set_registers(tp, index, type | byen, 4, data);
 	}
 
 error1:
-- 
2.41.0