i2c-designware: Set Tx/Rx FIFO threshold levels

As a hardware feature, DW I2C core generates a STOP condition whenever
the Tx FIFO becomes empty (strictly speaking, whenever the last byte in
the Tx FIFO is sent out), even if we have more bytes to be written.

In other words, we must never make "Tx FIFO underrun" happen during
a transaction, except for the last byte.  For the safety's sake, we'd
make TX_EMPTY interrupt get triggered every time one byte is processed.

The Rx FIFO threshold needs to be set as well.

Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi@necel.com>
Acked-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

diff --git a/drivers/i2c/busses/i2c-designware.c b/drivers/i2c/busses/i2c-designware.c
index 5fce1a0..0eea0dd 100644 (file)
--- a/drivers/i2c/busses/i2c-designware.c
+++ b/drivers/i2c/busses/i2c-designware.c
@@ -50,6 +50,8 @@
 #define DW_IC_INTR_STAT                0x2c
 #define DW_IC_INTR_MASK                0x30
 #define DW_IC_RAW_INTR_STAT    0x34
+#define DW_IC_RX_TL            0x38
+#define DW_IC_TX_TL            0x3c
 #define DW_IC_CLR_INTR         0x40
 #define DW_IC_CLR_RX_UNDER     0x44
 #define DW_IC_CLR_RX_OVER      0x48
@@ -295,6 +297,10 @@ static void i2c_dw_init(struct dw_i2c_dev *dev)
        writel(lcnt, dev->base + DW_IC_FS_SCL_LCNT);
        dev_dbg(dev->dev, "Fast-mode HCNT:LCNT = %d:%d\n", hcnt, lcnt);
 
+       /* Configure Tx/Rx FIFO threshold levels */
+       writel(dev->tx_fifo_depth - 1, dev->base + DW_IC_TX_TL);
+       writel(0, dev->base + DW_IC_RX_TL);
+
        /* configure the i2c master */
        ic_con = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
                DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;