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Subject[PATCH] i2c-bfin-twi: handle faulty slave devices better
Date
From: Michael Hennerich <michael.hennerich@analog.com>

Faulty slave devices might drive SDA low after a transfer finishes. So,
when this scenario is detected, have the master generate up to 8 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>
---
Note: this requires the existing Blackfin TWI patches already sent out
drivers/i2c/busses/i2c-bfin-twi.c | 22 ++++++++++++++++++++++
1 files changed, 22 insertions(+), 0 deletions(-)
diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
index fb26e5c..f9c05e1 100644
--- a/drivers/i2c/busses/i2c-bfin-twi.c
+++ b/drivers/i2c/busses/i2c-bfin-twi.c
@@ -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 salve devices, may drive SDA low after a transfer
+ * finishes. To release the bus this code generates up to 8
+ * extra clocks until SDA is released.
+ */
+
+ if (read_MASTER_STAT(iface) & SDASEN) {
+ int cnt = 8;
+ 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.
*/
--
1.7.1


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