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i2c: i2c-bfin-twi: Illegal i2c bus lock upon certain transfer scenarios. 

For transfer counts > 255 bytes i2c-bfin-twi sets the data
transfer counter DCNT to 0xFF indicating unlimited transfers.
It then uses a flag iface->manual_stop to manually issue the STOP
condition, once the required amount of bytes are received.

We found that on I2C receive operation issuing the STOP condition
together with a FULL RCV FIFO (2bytes) will cause SDA and SCL be
constantly driven low.

Temporary workaround until further investigation:
Discard the RCV FIFO before issuing the STOP condition.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
This commit is contained in:
Michael Hennerich 2012-06-13 16:22:40 +08:00 committed by Wolfram Sang
parent d61a909515
commit 925594e035
1 changed files with 4 additions and 0 deletions
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4
drivers/i2c/busses/i2c-bfin-twi.c
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@ -131,6 +131,10 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface,
iface->transPtr++;
iface->readNum--;
} else if (iface->manual_stop) {
/* Temporary workaround to avoid possible bus stall -
* Flush FIFO before issuing the STOP condition
*/
read_RCV_DATA16(iface);
write_MASTER_CTL(iface,
read_MASTER_CTL(iface) | STOP);
} else if (iface->cur_mode == TWI_I2C_MODE_REPEAT &&