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 <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!
Sure, but I'm going to let the conversation we have about this issue in
another thread play out a little first.
--
Regards,
Nikita.
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