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authorNikita Kiryanov <nikita@compulab.co.il>2013-11-28 18:04:42 +0200
committerHeiko Schocher <hs@denx.de>2013-12-05 12:25:02 +0100
commit92c23c9226a23548c875e4ba0e493a0aac172e25 (patch)
treee7ee9e8152ac355fc1e6d7b989a371c176a1082b /drivers/i2c
parent6ca6d080d6c75a88709e8ba8d1e6d776bc01b68d (diff)
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arm: omap: i2c: don't zero cnt in i2c_write
Writing zero into I2Ci.I2C_CNT register causes random I2C failures in OMAP3 based devices. This seems to be related to the following advisory which apears in multiple erratas for OMAP3 SoCs (OMAP35xx, DM37xx), as well as OMAP4430 TRM: Advisory: 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. The writes in question are unnecessary from a functional point of view. Most of them are done after I/O has finished, and the only one that preceds I/O (in i2c_probe()) is also unnecessary because a stop bit is sent before actual data transmission takes place. Therefore, remove all writes that zero the cnt register. Cc: Heiko Schocher <hs@denx.de> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Cc: Tom Rini <trini@ti.com> Cc: Lubomir Popov <lpopov@mm-sol.com> Cc: Enric Balletbo Serra <eballetbo@gmail.com> Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il> Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Tested-by: Lubomir Popov <lpopov@mm-sol.com>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/omap24xx_i2c.c6
1 files changed, 0 insertions, 6 deletions
diff --git a/drivers/i2c/omap24xx_i2c.c b/drivers/i2c/omap24xx_i2c.c
index 3d38c03..c784004 100644
--- a/drivers/i2c/omap24xx_i2c.c
+++ b/drivers/i2c/omap24xx_i2c.c
@@ -158,7 +158,6 @@ static void omap24_i2c_init(struct i2c_adapter *adap, int speed, int slaveadd)
udelay(1000);
flush_fifo(adap);
writew(0xFFFF, &i2c_base->stat);
- writew(0, &i2c_base->cnt);
}
static void flush_fifo(struct i2c_adapter *adap)
@@ -198,8 +197,6 @@ static int omap24_i2c_probe(struct i2c_adapter *adap, uchar chip)
return res;
/* No data transfer, slave addr only */
- writew(0, &i2c_base->cnt);
- /* Set slave address */
writew(chip, &i2c_base->sa);
/* Stop bit needed here */
writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_TRX |
@@ -234,7 +231,6 @@ static int omap24_i2c_probe(struct i2c_adapter *adap, uchar chip)
pr_exit:
flush_fifo(adap);
writew(0xFFFF, &i2c_base->stat);
- writew(0, &i2c_base->cnt);
return res;
}
@@ -372,7 +368,6 @@ static int omap24_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr,
rd_exit:
flush_fifo(adap);
writew(0xFFFF, &i2c_base->stat);
- writew(0, &i2c_base->cnt);
return i2c_error;
}
@@ -473,7 +468,6 @@ static int omap24_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
wr_exit:
flush_fifo(adap);
writew(0xFFFF, &i2c_base->stat);
- writew(0, &i2c_base->cnt);
return i2c_error;
}