From 7e78f7ad7f7f666598bc2ff115ea7a35f8e059f1 Mon Sep 17 00:00:00 2001
From: Dirk Eibach <dirk.eibach@gdsys.cc>
Date: Wed, 29 Oct 2014 15:56:43 +0100
Subject: [PATCH] ppc4xx: Fix i2c repeated start
Debugging some i2c trouble I saw on my scope that repeated
start is not working properply. The 4xx even held clock pulled down
after transfers. Having a look in the driver I realized
that IIC_CNTL_RPST is set on that part of the transfer that should
begin with a repeated start. But repeated start is about not sending a
stop condition, so IIC_CNTL_RPST has to be set on the last transfer
before the repeated start happens.
Signed-off-by: Dirk Eibach <dirk.eibach@gdsys.cc>
Reviewed-by: Stefan Roese <sr@denx.de>
---
drivers/i2c/ppc4xx_i2c.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/i2c/ppc4xx_i2c.c b/drivers/i2c/ppc4xx_i2c.c
index e7a15ba644..d2ff86c99a 100644
--- a/drivers/i2c/ppc4xx_i2c.c
+++ b/drivers/i2c/ppc4xx_i2c.c
@@ -158,8 +158,7 @@ static void ppc4xx_i2c_init(struct i2c_adapter *adap, int speed, int slaveaddr)
*
* Typical case is a Write of an addr followd by a Read. The
* IBM FAQ does not cover this. On the last byte of the write
- * we don't set the creg CHT bit, and on the first bytes of the
- * read we set the RPST bit.
+ * we don't set the creg CHT bit but the RPST bit.
*
* It does not support address only transfers, there must be
* a data part. If you want to write the address yourself, put
@@ -247,6 +246,10 @@ static int _i2c_transfer(struct i2c_adapter *adap,
if ((!cmd_type && (ptr == addr)) || ((tran + bc) != cnt))
creg |= IIC_CNTL_CHT;
+ /* last part of address, prepare for repeated start on read */
+ if (cmd_type && (ptr == addr) && ((tran + bc) == cnt))
+ creg |= IIC_CNTL_RPST;
+
if (reading) {
creg |= IIC_CNTL_READ;
} else {
@@ -314,8 +317,6 @@ static int _i2c_transfer(struct i2c_adapter *adap,
cnt = data_len;
tran = 0;
reading = cmd_type;
- if (reading)
- creg = IIC_CNTL_RPST;
}
}
return result;
--
2.39.5