i2c: Fix NACK detection in i2c-pasemi
Turns out we don't actually check the status to see if there was a
device out there to talk to, just if we had a timeout when doing so.
Add the proper check, so we don't falsly think there are devices
on the bus that are not there, etc.
Signed-off-by: Olof Johansson <olof at lixom.net>
---
On Wed, Oct 24, 2007 at 01:51:09PM +0200, Jean Delvare wrote:
> The question is, how do you manage to get that many errors reported,
> when I don't get any when loading the lm90 driver, despite the 6 I2C
> buses on my system. When you reach this point in the lm90 driver, it
> means that i2c-core successfully probed that there was a device at said
> address on the given bus. I have a hard time believing that you have
> chips at 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, 0x4c, 0x4d and 0x4e on 3
> different I2C buses on your system.
>
> It sounds like the underlying bus driver is broken and report chips
> where they aren't. What are these I2C buses? Their driver(s) needs
> fixing.
Crap, yeah, you're right. This was the only driver behaving this way
for me, and I didn't have another controller to test on.
The bug is indeed in our bus driver, we don't check for NACK's, only
timeouts (I was of the impresison that a nack would cause a timeout,
but that's obviously wrong).
Patch below. Thanks a bunch!
-Olof
diff --git a/drivers/i2c/busses/i2c-pasemi.c b/drivers/i2c/busses/i2c-pasemi.c
index 58e3271..a1d339e 100644
--- a/drivers/i2c/busses/i2c-pasemi.c
+++ b/drivers/i2c/busses/i2c-pasemi.c
@@ -51,6 +51,7 @@ struct pasemi_smbus {
#define MRXFIFO_DATA_M 0x000000ff
#define SMSTA_XEN 0x08000000
+#define SMSTA_MTN 0x00200000
#define CTL_MRR 0x00000400
#define CTL_MTR 0x00000200
@@ -98,6 +99,10 @@ static unsigned int pasemi_smb_waitready(struct pasemi_smbus *smbus)
status = reg_read(smbus, REG_SMSTA);
}
+ /* Got NACK? */
+ if (status & SMSTA_MTN)
+ return -ENODEV;
+
if (timeout < 0) {
dev_warn(&smbus->dev->dev, "Timeout, status 0x%08x\n", status);
reg_write(smbus, REG_SMSTA, status);
