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

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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>
This commit is contained in:
Domen Puncer 2007-07-12 14:12:31 +02:00 committed by Jean Delvare
parent 1b144df1d7
commit 254db9b5e7
1 changed files with 23 additions and 0 deletions
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23
drivers/i2c/busses/i2c-mpc.c
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@ -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();