Message ID | 1385563449-15094-1-git-send-email-nikita@compulab.co.il |
---|---|
State | Superseded |
Delegated to: | Heiko Schocher |
Headers | show |
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 <hs@denx.de> > Signed-off-by: Nikita Kiryanov <nikita@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!
On 11/27/2013 05:09 PM, Tom Rini wrote: > 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 <hs@denx.de> >> Signed-off-by: Nikita Kiryanov <nikita@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! > Sure, but I'm going to let the conversation we have about this issue in another thread play out a little first.
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; }
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 <hs@denx.de> Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il> --- drivers/i2c/omap24xx_i2c.c | 3 +++ 1 file changed, 3 insertions(+)