[U-Boot] [PATCH] arm: omap3: i2c: don't zero cnt in i2c_write

[Nikita Kiryanov]

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 at denx.de>
Signed-off-by: Nikita Kiryanov <nikita at 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;
 }
 
-- 
1.8.1.2