i2c-bfin-twi: handle faulty slave devices better

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>

diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
index fb26e5c..1ee9d5a 100644 (file)
--- 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 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.
                 */