i2c-designware: Divide i2c_dw_xfer_msg into two functions

We have some steps at the top of i2c_dw_xfer_msg() to set up a slave
address and enable DW I2C core.  And it's executed only when we don't
have STATUS_WRITE_IN_PROGRESS.

But we need to make sure that STATUS_WRITE_IN_PROGRESS only indicates
that we have a pending i2c_msg to process.  In other words, even if
STATUS_WRITE_IN_PROGRESS is not set, that doesn't mean we're at initial
state in the I2C transaction.

Since i2c_dw_xfer_msg() will be invoked again and again during a
transaction, those init steps have a possibility to be re-processed
needlessly.  For example, this issue easily takes place when processing
a combined transaction with a certain condition (the number of tx bytes
in the first i2c_msg, equals to the Tx FIFO depth).

Consequently we should not use STATUS_WRITE_IN_PROGRESS to determine
where we're at in an I2C transaction.  It would be better to separate
those initialization steps from i2c_dw_xfer_msg().

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>

1 files changed, 25 insertions, 20 deletions

diff --git a/drivers/i2c/busses/i2c-designware.c b/drivers/i2c/busses/i2c-designware.c
index 940bbf31bc8c..da5612b21aff 100644
--- a/drivers/i2c/busses/i2c-designware.c
+++ b/drivers/i2c/busses/i2c-designware.c
@@ -326,6 +326,29 @@ static int i2c_dw_wait_bus_not_busy(struct dw_i2c_dev *dev)
         return 0;
 }
 
+static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
+{
+        struct i2c_msg *msgs = dev->msgs;
+        u32 ic_con;
+
+        /* Disable the adapter */
+        writel(0, dev->base + DW_IC_ENABLE);
+
+        /* set the slave (target) address */
+        writel(msgs[dev->msg_write_idx].addr, dev->base + DW_IC_TAR);
+
+        /* if the slave address is ten bit address, enable 10BITADDR */
+        ic_con = readl(dev->base + DW_IC_CON);
+        if (msgs[dev->msg_write_idx].flags & I2C_M_TEN)
+                ic_con |= DW_IC_CON_10BITADDR_MASTER;
+        else
+                ic_con &= ~DW_IC_CON_10BITADDR_MASTER;
+        writel(ic_con, dev->base + DW_IC_CON);
+
+        /* Enable the adapter */
+        writel(1, dev->base + DW_IC_ENABLE);
+}
+
 /*
  * Initiate low level master read/write transaction.
  * This function is called from i2c_dw_xfer when starting a transfer.
@@ -336,7 +359,7 @@ static void
 i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 {
         struct i2c_msg *msgs = dev->msgs;
-        u32 ic_con, intr_mask;
+        u32 intr_mask;
         int tx_limit = dev->tx_fifo_depth - readl(dev->base + DW_IC_TXFLR);
         int rx_limit = dev->rx_fifo_depth - readl(dev->base + DW_IC_RXFLR);
         u32 addr = msgs[dev->msg_write_idx].addr;
@@ -344,25 +367,6 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 
         intr_mask = DW_IC_INTR_STOP_DET | DW_IC_INTR_TX_ABRT | DW_IC_INTR_RX_FULL;
 
-        if (!(dev->status & STATUS_WRITE_IN_PROGRESS)) {
-                /* Disable the adapter */
-                writel(0, dev->base + DW_IC_ENABLE);
-
-                /* set the slave (target) address */
-                writel(msgs[dev->msg_write_idx].addr, dev->base + DW_IC_TAR);
-
-                /* if the slave address is ten bit address, enable 10BITADDR */
-                ic_con = readl(dev->base + DW_IC_CON);
-                if (msgs[dev->msg_write_idx].flags & I2C_M_TEN)
-                        ic_con |= DW_IC_CON_10BITADDR_MASTER;
-                else
-                        ic_con &= ~DW_IC_CON_10BITADDR_MASTER;
-                writel(ic_con, dev->base + DW_IC_CON);
-
-                /* Enable the adapter */
-                writel(1, dev->base + DW_IC_ENABLE);
-        }
-
         for (; dev->msg_write_idx < dev->msgs_num; dev->msg_write_idx++) {
                 /* if target address has changed, we need to
                  * reprogram the target address in the i2c
@@ -474,6 +478,7 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
                 goto done;
 
         /* start the transfers */
+        i2c_dw_xfer_init(dev);
         i2c_dw_xfer_msg(dev);
 
         /* wait for tx to complete */