summaryrefslogtreecommitdiffstats
path: root/drivers/i2c
diff options
context:
space:
mode:
authorAlexander Stein <alexander.stein@systec-electronic.com>2013-01-28 10:44:12 +0100
committerWolfram Sang <wolfram@the-dreams.de>2013-02-11 15:53:49 +0100
commitb08369a174a183e88baa98ab5e3566a617a3a7f8 (patch)
tree63a3d942b41b6dca13e6d770fddb2937f34ebbca /drivers/i2c
parenti2c: at91: fix unsed variable warning when building with !CONFIG_OF (diff)
downloadlinux-b08369a174a183e88baa98ab5e3566a617a3a7f8.tar.xz
linux-b08369a174a183e88baa98ab5e3566a617a3a7f8.zip
i2c: isch: Add module parameter for backbone clock rate if divider is unset
It was observed the Host Clock Divider was not written by the driver. It was still set to (default) 0, if not already set by BIOS, which caused garbage on SMBus. This driver adds a parameters which is used to calculate the divider appropriately for a default bitrate of 100 KHz. This new divider is only applied if the clock divider is still default 0. Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com> Reviewed-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Wolfram Sang <wolfram@the-dreams.de>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-isch.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-isch.c b/drivers/i2c/busses/i2c-isch.c
index 4099f79c2280..8c38aaa7417c 100644
--- a/drivers/i2c/busses/i2c-isch.c
+++ b/drivers/i2c/busses/i2c-isch.c
@@ -40,6 +40,7 @@
/* SCH SMBus address offsets */
#define SMBHSTCNT (0 + sch_smba)
#define SMBHSTSTS (1 + sch_smba)
+#define SMBHSTCLK (2 + sch_smba)
#define SMBHSTADD (4 + sch_smba) /* TSA */
#define SMBHSTCMD (5 + sch_smba)
#define SMBHSTDAT0 (6 + sch_smba)
@@ -58,6 +59,9 @@
static unsigned short sch_smba;
static struct i2c_adapter sch_adapter;
+static int backbone_speed = 33000; /* backbone speed in kHz */
+module_param(backbone_speed, int, S_IRUSR | S_IWUSR);
+MODULE_PARM_DESC(backbone_speed, "Backbone speed in kHz, (default = 33000)");
/*
* Start the i2c transaction -- the i2c_access will prepare the transaction
@@ -156,6 +160,19 @@ static s32 sch_access(struct i2c_adapter *adap, u16 addr,
dev_dbg(&sch_adapter.dev, "SMBus busy (%02x)\n", temp);
return -EAGAIN;
}
+ temp = inw(SMBHSTCLK);
+ if (!temp) {
+ /*
+ * We can't determine if we have 33 or 25 MHz clock for
+ * SMBus, so expect 33 MHz and calculate a bus clock of
+ * 100 kHz. If we actually run at 25 MHz the bus will be
+ * run ~75 kHz instead which should do no harm.
+ */
+ dev_notice(&sch_adapter.dev,
+ "Clock divider unitialized. Setting defaults\n");
+ outw(backbone_speed / (4 * 100), SMBHSTCLK);
+ }
+
dev_dbg(&sch_adapter.dev, "access size: %d %s\n", size,
(read_write)?"READ":"WRITE");
switch (size) {