rockchip: i2c: fix >32 byte reads

The hw can read up to 32 bytes at a time. If we need
more than one chunk, we have to enter the plain RX mode.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

drivers/i2c/rk_i2c.c

@@ -164,6 +164,7 @@ static int rk_i2c_read(struct rk_i2c *i2c, uchar chip, uint reg, uint r_len,
 	uint rxdata;
 	uint i, j;
 	int err;
+	bool snd_chunk = false;
 
 	debug("rk_i2c_read: chip = %d, reg = %d, r_len = %d, b_len = %d\n",
 	      chip, reg, r_len, b_len);
@@ -184,15 +185,26 @@ static int rk_i2c_read(struct rk_i2c *i2c, uchar chip, uint reg, uint r_len,
 
 	while (bytes_remain_len) {
 		if (bytes_remain_len > RK_I2C_FIFO_SIZE) {
-			con = I2C_CON_EN | I2C_CON_MOD(I2C_MODE_TRX);
+			con = I2C_CON_EN;
 			bytes_xferred = 32;
 		} else {
-			con = I2C_CON_EN | I2C_CON_MOD(I2C_MODE_TRX) |
-				I2C_CON_LASTACK;
+			/*
+			 * The hw can read up to 32 bytes at a time. If we need
+			 * more than one chunk, send an ACK after the last byte.
+			 */
+			con = I2C_CON_EN | I2C_CON_LASTACK;
 			bytes_xferred = bytes_remain_len;
 		}
 		words_xferred = DIV_ROUND_UP(bytes_xferred, 4);
 
+		/*
+		 * make sure we are in plain RX mode if we read a second chunk
+		 */
+		if (snd_chunk)
+			con |= I2C_CON_MOD(I2C_MODE_RX);
+		else
+			con |= I2C_CON_MOD(I2C_MODE_TRX);
+
 		writel(con, &regs->con);
 		writel(bytes_xferred, &regs->mrxcnt);
 		writel(I2C_MBRFIEN | I2C_NAKRCVIEN, &regs->ien);
@@ -227,6 +239,7 @@ static int rk_i2c_read(struct rk_i2c *i2c, uchar chip, uint reg, uint r_len,
 		}
 
 		bytes_remain_len -= bytes_xferred;
+		snd_chunk = true;
 		debug("I2C Read bytes_remain_len %d\n", bytes_remain_len);
 	}