[PATCH 1/2] i2c-bfin-twi: handle faulty slave devices better

[PATCH 1/2] i2c-bfin-twi: handle faulty slave devices better

[Mike Frysinger]

From: Michael Hennerich <michael.hennerich-OyLXuOCK7orQT0dZR+AlfA@public.gmane.org>

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-OyLXuOCK7orQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>
---
 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..1ee9d5a 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 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.
 		 */
-- 
1.7.4.rc1

[PATCH 2/2] i2c-bfin-twi: move setup to the earlier subsys initcall

[Mike Frysinger]

From: Michael Hennerich <michael.hennerich-OyLXuOCK7orQT0dZR+AlfA@public.gmane.org>

Some systems using this bus sometimes have very basic devices such as
regulators on the bus, so the I2C bus master needs to be loaded early.
This also matches the behavior of many other I2C bus master drivers.
Therefore initialize via subsys_initcall().

Signed-off-by: Michael Hennerich <michael.hennerich-OyLXuOCK7orQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>
---
 drivers/i2c/busses/i2c-bfin-twi.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
index 1ee9d5a..52b545a 100644
--- a/drivers/i2c/busses/i2c-bfin-twi.c
+++ b/drivers/i2c/busses/i2c-bfin-twi.c
@@ -782,7 +782,7 @@ static void __exit i2c_bfin_twi_exit(void)
 	platform_driver_unregister(&i2c_bfin_twi_driver);
 }
 
-module_init(i2c_bfin_twi_init);
+subsys_initcall(i2c_bfin_twi_init);
 module_exit(i2c_bfin_twi_exit);
 
 MODULE_AUTHOR("Bryan Wu, Sonic Zhang");
-- 
1.7.4.rc1