On Wed, Nov 27, 2013 at 04:44:09PM +0200, Nikita Kiryanov wrote: > The zeroing of I2Ci.I2C_CNT register at the end of i2c_write causes > random I2C failures in OMAP3 based devices. This is probably related > to the following advisory in OMAP3 errata: > > I2C Module Does Not Allow 0-Byte Data Requests > Details: > When configured as the master, the I2C module does not allow 0-byte data > transfers. Note: Programming I2Ci.I2C_CNT[15:0]: DCOUNT = 0 will cause > undefined behavior. > Workaround(s): > No workaround. Do not use 0-byte data requests. > > Make the write conditional so that only non-OMAP3 devices will perform it. > > Cc: Heiko Schocher <h...@denx.de> > Signed-off-by: Nikita Kiryanov <nik...@compulab.co.il> > --- > drivers/i2c/omap24xx_i2c.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c > index 3d38c03..2862a8f 100644 > --- a/drivers/i2c/omap24xx_i2c.c > +++ b/drivers/i2c/omap24xx_i2c.c > @@ -473,7 +473,10 @@ static int omap24_i2c_write(struct i2c_adapter *adap, > uchar chip, uint addr, > wr_exit: > flush_fifo(adap); > writew(0xFFFF, &i2c_base->stat); > + /* This write is known to cause undefined behavior on OMAP3 */ > +#ifndef CONFIG_OMAP34XX > writew(0, &i2c_base->cnt); > +#endif > return i2c_error; > }
Yay for tracking this down. Can you please expand the comment to mention the specific advisory? Thanks! -- Tom
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