From b97cd6814ec08be56225975a050ee486bfa7c13a Mon Sep 17 00:00:00 2001
From: Dirk Eibach <dirk.eibach@gdsys.cc>
Date: Wed, 29 Oct 2014 15:56:44 +0100
Subject: [PATCH] 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>
---
arch/powerpc/include/asm/ppc4xx-i2c.h | 2 ++
drivers/i2c/ppc4xx_i2c.c | 21 +++++++++++++++++++++
2 files changed, 23 insertions(+)
diff --git a/arch/powerpc/include/asm/ppc4xx-i2c.h b/arch/powerpc/include/asm/ppc4xx-i2c.h
index 09189cf19b..df97f175b3 100644
--- 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 d2ff86c99a..df8888550b 100644
--- 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;
}
--
2.39.5