ppc4xx: Handle i2c stuck on combined xfer

ppc4xx i2c master gets stuck on errors while repeated start is
active. Can be easily reproduced by "i2c md" on an unpopulated
i2c address. There is not stop condition given, scl remains
pulled low.
The only way out seems to be doing a stop manually and then a
soft reset.

Signed-off-by: Dirk Eibach <dirk.eibach@gdsys.cc>
Reviewed-by: Stefan Roese <sr@denx.de>

diff --git a/arch/powerpc/include/asm/ppc4xx-i2c.h b/arch/powerpc/include/asm/ppc4xx-i2c.h
index 09189cf..df97f17 100644 (file)
--- a/arch/powerpc/include/asm/ppc4xx-i2c.h
+++ b/arch/powerpc/include/asm/ppc4xx-i2c.h
@@ -72,6 +72,8 @@ struct ppc4xx_i2c {
 #define IIC_EXTSTS_XFRA                0x01
 #define IIC_EXTSTS_ICT         0x02
 #define IIC_EXTSTS_LA          0x04
+#define IIC_EXTSTS_BCS_MASK    0x70
+#define IIC_EXTSTS_BCS_FREE    0x40
 
 /* XTCNTLSS Register Bit definition */
 #define IIC_XTCNTLSS_SRST      0x01

diff --git a/drivers/i2c/ppc4xx_i2c.c b/drivers/i2c/ppc4xx_i2c.c
index d2ff86c..df88885 100644 (file)
--- a/drivers/i2c/ppc4xx_i2c.c
+++ b/drivers/i2c/ppc4xx_i2c.c
@@ -289,6 +289,27 @@ static int _i2c_transfer(struct i2c_adapter *adap,
                        /* Transfer aborted? */
                        if (status & IIC_EXTSTS_XFRA)
                                result = IIC_NOK_XFRA;
+                       /* Is bus free?
+                        * If error happened during combined xfer
+                        * IIC interface is usually stuck in some strange
+                        * state without a valid stop condition.
+                        * Brute, but working: generate stop, then soft reset.
+                        */
+                       if ((status & IIC_EXTSTS_BCS_MASK)
+                           != IIC_EXTSTS_BCS_FREE){
+                               u8 mdcntl = in_8(&i2c->mdcntl);
+
+                               /* Generate valid stop condition */
+                               out_8(&i2c->xtcntlss, IIC_XTCNTLSS_SRST);
+                               out_8(&i2c->directcntl, IIC_DIRCNTL_SCC);
+                               udelay(10);
+                               out_8(&i2c->directcntl,
+                                     IIC_DIRCNTL_SCC | IIC_DIRCNTL_SDAC);
+                               out_8(&i2c->xtcntlss, 0);
+
+                               ppc4xx_i2c_init(adap, (mdcntl & IIC_MDCNTL_FSM)
+                                               ? 400000 : 100000, 0);
+                       }
                } else if ( status & IIC_STS_PT) {
                        result = IIC_NOK_TOUT;
                }