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i2c-bfin-twi: handle faulty slave devices better

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Faulty slave devices might drive SDA low after a transfer finishes.  So,
when this scenario is detected, have the master generate up to 9 extra
clocks until the SDA is properly released.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
This commit is contained in:
Michael Hennerich 2011-01-11 00:25:08 -05:00 committed by Ben Dooks
parent f878133bf0
commit 540ac5553e
1 changed files with 22 additions and 0 deletions
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22
drivers/i2c/busses/i2c-bfin-twi.c
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@ -20,6 +20,7 @@
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <asm/blackfin.h>
#include <asm/portmux.h>
@ -159,6 +160,27 @@ static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface,
if (mast_stat & BUFWRERR)
dev_dbg(&iface->adap.dev, "Buffer Write Error\n");
/* Faulty slave devices, may drive SDA low after a transfer
* finishes. To release the bus this code generates up to 9
* extra clocks until SDA is released.
*/
if (read_MASTER_STAT(iface) & SDASEN) {
int cnt = 9;
do {
write_MASTER_CTL(iface, SCLOVR);
udelay(6);
write_MASTER_CTL(iface, 0);
udelay(6);
} while ((read_MASTER_STAT(iface) & SDASEN) && cnt--);
write_MASTER_CTL(iface, SDAOVR | SCLOVR);
udelay(6);
write_MASTER_CTL(iface, SDAOVR);
udelay(6);
write_MASTER_CTL(iface, 0);
}
/* If it is a quick transfer, only address without data,
* not an err, return 1.
*/