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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>
This commit is contained in:
Shinya Kuribayashi 2009-11-06 21:48:55 +09:00 committed by Ben Dooks
parent 21a89d4101
commit 81e798b73a
1 changed files with 25 additions and 20 deletions
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45
drivers/i2c/busses/i2c-designware.c
View File

@ -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 */