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[PATCH 12/16] i2c-designware: Divide i2c_dw_xfer_msg into two functions

To: baruch@tkos.co.il, linux-i2c@vger.kernel.org
Subject: [PATCH 12/16] i2c-designware: Divide i2c_dw_xfer_msg into two functions
From: Shinya Kuribayashi <shinya.kuribayashi@necel.com>
Date: Tue, 13 Oct 2009 11:52:49 +0900
Cc: ben-linux@fluff.org, linux-mips@linux-mips.org, linux-arm-kernel@lists.infradead.org
In-reply-to: <4AD3E974.8080200@necel.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <4AD3E974.8080200@necel.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Thunderbird 2.0.0.23 (Windows/20090812)
We have some steps at the top of i2c_dw_xfer_msg() to set up the slave
address and enable the DW I2C core.  It's executed only when we don't
have STATUS_WRITE_IN_PROGRESS.

Then 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 the
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 == Tx FIFO depth).

Consequently we should not use STATUS_WRITE_IN_PROGRESS to determine
where we're at in the I2C transaction, then let's separate those
initialization steps from i2c_dw_xfer_msg().

Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi@necel.com>
---
drivers/i2c/busses/i2c-designware.c |   45 +++++++++++++++++++---------------
1 files changed, 25 insertions(+), 20 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware.c 
b/drivers/i2c/busses/i2c-designware.c
index d9b5790..de006f0 100644
--- a/drivers/i2c/busses/i2c-designware.c
+++ b/drivers/i2c/busses/i2c-designware.c
@@ -325,6 +325,29 @@ 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.
@@ -335,31 +358,12 @@ 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;
        u32 buf_len = dev->tx_buf_len;

-       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 */
--
1.6.5


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