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>

1 files changed, 20 insertions, 6 deletions

diff --git a/drivers/i2c/busses/i2c-s3c2410.c b/drivers/i2c/busses/i2c-s3c2410.c
index 3eb5958f347..e8395be0d92 100644
--- 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,