i2c-s3c2410: Fix I2C SDA to SCL setup time

Fix the setup time for SDA to SCL due to the way
the S3C24XX I2C controller works.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index 3eb5958..e8395be 100644 (file)
--- a/drivers/i2c/busses/i2c-s3c2410.c
+++ b/drivers/i2c/busses/i2c-s3c2410.c
@@ -61,6 +61,8 @@ struct s3c24xx_i2c {
        unsigned int            msg_idx;
        unsigned int            msg_ptr;
 
+       unsigned int            tx_setup;
+
        enum s3c24xx_i2c_state  state;
 
        void __iomem            *regs;
@@ -199,8 +201,11 @@ static void s3c24xx_i2c_message_start(struct s3c24xx_i2c *i2c,
        dev_dbg(i2c->dev, "START: %08lx to IICSTAT, %02x to DS\n", stat, addr);
        writeb(addr, i2c->regs + S3C2410_IICDS);
        
-       // delay a bit and reset iiccon before setting start (per samsung)
-       udelay(1);
+       /* delay here to ensure the data byte has gotten onto the bus
+        * before the transaction is started */
+
+       ndelay(i2c->tx_setup);
+
        dev_dbg(i2c->dev, "iiccon, %08lx\n", iiccon);
        writel(iiccon, i2c->regs + S3C2410_IICCON);
        
@@ -322,7 +327,15 @@ static int i2s_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat)
                if (!is_msgend(i2c)) {
                        byte = i2c->msg->buf[i2c->msg_ptr++];
                        writeb(byte, i2c->regs + S3C2410_IICDS);
-                       
+
+                       /* delay after writing the byte to allow the
+                        * data setup time on the bus, as writing the
+                        * data to the register causes the first bit
+                        * to appear on SDA, and SCL will change as
+                        * soon as the interrupt is acknowledged */
+
+                       ndelay(i2c->tx_setup);
+
                } else if (!is_lastmsg(i2c)) {
                        /* we need to go to the next i2c message */
 
@@ -570,9 +583,10 @@ static const struct i2c_algorithm s3c24xx_i2c_algorithm = {
 };
 
 static struct s3c24xx_i2c s3c24xx_i2c = {
-       .lock   = __SPIN_LOCK_UNLOCKED(s3c24xx_i2c.lock),
-       .wait   = __WAIT_QUEUE_HEAD_INITIALIZER(s3c24xx_i2c.wait),
-       .adap   = {
+       .lock           = __SPIN_LOCK_UNLOCKED(s3c24xx_i2c.lock),
+       .wait           = __WAIT_QUEUE_HEAD_INITIALIZER(s3c24xx_i2c.wait),
+       .tx_setup       = 50,
+       .adap           = {
                .name                   = "s3c2410-i2c",
                .owner                  = THIS_MODULE,
                .algo                   = &s3c24xx_i2c_algorithm,