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| author | Domen Puncer <domen.puncer@telargo.com> | 2007-07-12 14:12:31 +0200 |
|---|---|---|
| committer | Jean Delvare <khali@hyperion.delvare> | 2007-07-12 14:12:31 +0200 |
| commit | 254db9b5e7b1b0d38a4f177c2c23a5685c78221a (patch) | |
| tree | 10dffafbbf287d61194fbe885a7e977de2d88242 /drivers/i2c | |
| parent | 1b144df1d7d69d6dd3394205933c8951dd8b6784 (diff) | |
| download | linux-254db9b5e7b1b0d38a4f177c2c23a5685c78221a.tar.bz2 | |
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>
Diffstat (limited to 'drivers/i2c')
| -rw-r--r-- | drivers/i2c/busses/i2c-mpc.c | 23 |
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(); |