i2c-mpc: work around missing-9th-clock-pulse bug

Work around a problem reported on:
http://ozlabs.org/pipermail/linuxppc-embedded/2005-July/019038.html
Without this patch I2C on mpc5200 becomes unusable after a while.
Tested on mpc5200 boards by Matthias Fechner and me.

Signed-off-by: Domen Puncer <domen.puncer@telargo.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index a769efc7f408..851c3ed513d0 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -74,6 +74,25 @@ static irqreturn_t mpc_i2c_isr(int irq, void *dev_id)
         return IRQ_HANDLED;
 }
 
+/* Sometimes 9th clock pulse isn't generated, and slave doesn't release
+ * the bus, because it wants to send ACK.
+ * Following sequence of enabling/disabling and sending start/stop generates
+ * the pulse, so it's all OK.
+ */
+static void mpc_i2c_fixup(struct mpc_i2c *i2c)
+{
+        writeccr(i2c, 0);
+        udelay(30);
+        writeccr(i2c, CCR_MEN);
+        udelay(30);
+        writeccr(i2c, CCR_MSTA | CCR_MTX);
+        udelay(30);
+        writeccr(i2c, CCR_MSTA | CCR_MTX | CCR_MEN);
+        udelay(30);
+        writeccr(i2c, CCR_MEN);
+        udelay(30);
+}
+
 static int i2c_wait(struct mpc_i2c *i2c, unsigned timeout, int writing)
 {
         unsigned long orig_jiffies = jiffies;
@@ -153,6 +172,7 @@ static void mpc_i2c_start(struct mpc_i2c *i2c)
 static void mpc_i2c_stop(struct mpc_i2c *i2c)
 {
         writeccr(i2c, CCR_MEN);
+        writeccr(i2c, 0);
 }
 
 static int mpc_write(struct mpc_i2c *i2c, int target,
@@ -245,6 +265,9 @@ static int mpc_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
                 }
                 if (time_after(jiffies, orig_jiffies + HZ)) {
                         pr_debug("I2C: timeout\n");
+                        if (readb(i2c->base + MPC_I2C_SR) ==
+                            (CSR_MCF | CSR_MBB | CSR_RXAK))
+                                mpc_i2c_fixup(i2c);
                         return -EIO;
                 }
                 schedule();