[PATCH v6 04/48] Input: atmel_mxt_ts - split large i2c transfers into blocks

[Jiada Wang]

From: Nick Dyer <nick.dyer@xxxxxxxxxxx>

On some firmware variants, the size of the info block exceeds what can
be read in a single transfer.

Signed-off-by: Nick Dyer <nick.dyer@xxxxxxxxxxx>
(cherry picked from ndyer/linux/for-upstream commit 74c4f5277cfa403d43fafc404119dc57a08677db)
[gdavis: Forward port and fix conflicts due to v4.14.51 commit
	 960fe000b1d3 ("Input: atmel_mxt_ts - fix the firmware
	 update").]
Signed-off-by: George G. Davis <george_davis@xxxxxxxxxx>
[jiada: Change mxt_read_blks() to __mxt_read_reg(), original __mxt_read_reg() to
	__mxt_read_chunk()]
Signed-off-by: Jiada Wang <jiada_wang@xxxxxxxxxx>
---
 drivers/input/touchscreen/atmel_mxt_ts.c | 28 +++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c b/drivers/input/touchscreen/atmel_mxt_ts.c
index ce5a069b62d4..9088b2d3266b 100644
--- a/drivers/input/touchscreen/atmel_mxt_ts.c
+++ b/drivers/input/touchscreen/atmel_mxt_ts.c
@@ -40,7 +40,7 @@
 #define MXT_OBJECT_START	0x07
 #define MXT_OBJECT_SIZE		6
 #define MXT_INFO_CHECKSUM_SIZE	3
-#define MXT_MAX_BLOCK_WRITE	256
+#define MXT_MAX_BLOCK_WRITE	255
 
 /* Object types */
 #define MXT_DEBUG_DIAGNOSTIC_T37	37
@@ -624,8 +624,8 @@ static int mxt_send_bootloader_cmd(struct mxt_data *data, bool unlock)
 	return 0;
 }
 
-static int __mxt_read_reg(struct i2c_client *client,
-			       u16 reg, u16 len, void *val)
+static int __mxt_read_chunk(struct i2c_client *client,
+			    u16 reg, u16 len, void *val)
 {
 	struct i2c_msg xfer[2];
 	u8 buf[2];
@@ -659,6 +659,28 @@ static int __mxt_read_reg(struct i2c_client *client,
 	return ret;
 }
 
+static int __mxt_read_reg(struct i2c_client *client,
+			  u16 reg, u16 len, void *buf)
+{
+	u16 offset = 0;
+	int error;
+	u16 size;
+
+	while (offset < len) {
+		size = min(MXT_MAX_BLOCK_WRITE, len - offset);
+
+		error = __mxt_read_chunk(client,
+					 reg + offset,
+					 size, buf + offset);
+		if (error)
+			return error;
+
+		offset += size;
+	}
+
+	return 0;
+}
+
 static int __mxt_write_reg(struct i2c_client *client, u16 reg, u16 len,
 			   const void *val)
 {
-- 
2.17.1