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

[Domen Puncer]

On 09/07/07 09:53 -0600, Grant Likely wrote:
> On 7/9/07, Domen Puncer <domen.puncer at telargo.com> wrote:
> >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 based boards by Matthias and me.
> >
> >Index: work-powerpc.git/drivers/i2c/busses/i2c-mpc.c
> >===================================================================
> >--- work-powerpc.git.orig/drivers/i2c/busses/i2c-mpc.c
> >+++ work-powerpc.git/drivers/i2c/busses/i2c-mpc.c
> >@@ -153,6 +167,9 @@ static void mpc_i2c_start(struct mpc_i2c
> > static void mpc_i2c_stop(struct mpc_i2c *i2c)
> > {
> >        writeccr(i2c, CCR_MEN);
> >+       mb();
> >+       writeccr(i2c, 0);
> >+       mb();
> > }
> 
> Are the mb() calls necessary?  The writeccr path includes eieio; is
> that not sufficient?

Right, v2:


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 and me.


Signed-off-by: Domen Puncer <domen.puncer at telargo.com>

---
 drivers/i2c/busses/i2c-mpc.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

Index: work-powerpc.git/drivers/i2c/busses/i2c-mpc.c
===================================================================
--- work-powerpc.git.orig/drivers/i2c/busses/i2c-mpc.c
+++ work-powerpc.git/drivers/i2c/busses/i2c-mpc.c
@@ -74,6 +74,20 @@ static irqreturn_t mpc_i2c_isr(int irq, 
 	return IRQ_HANDLED;
 }
 
+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 +167,7 @@ static void mpc_i2c_start(struct mpc_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 +260,8 @@ static int mpc_xfer(struct i2c_adapter *
 		}
 		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();