| Message ID | 1508806526-28489-1-git-send-email-linux@roeck-us.net (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
Hi Guenter, On Mon, 23 Oct 2017 17:55:26 -0700, Guenter Roeck wrote: > Commit 3d8f7a89a197 ("hwmon: (tmp102) Improve handling of initial read > delay") reduced the initial temperature read delay and made it dependent > on the chip's shutdown mode. If the chip was not in shutdown mode at probe, > the read delay no longer applies. > > This ignores the fact that the chip initialization changes the temperature > sensor resolution, and that the temperature register values change when > the resolution is changed. As a result, the reported temperature is twice > as high as the real temperature until the first temperature conversion > after the configuration change is complete. This can result in unexpected > behavior and, worst case, in a system shutdown. To fix the problem, > let's just always wait for a conversion to complete before reporting > a temperature. > > Fixes: 3d8f7a89a197 ("hwmon: (tmp102) Improve handling of initial read delay") > Link: https://bugzilla.kernel.org/show_bug.cgi?id=197167 > Reported-by: Ralf Goebel <ralf.goebel@imago-technologies.com> > Cc: Ralf Goebel <ralf.goebel@imago-technologies.com> > Signed-off-by: Guenter Roeck <linux@roeck-us.net> > --- > drivers/hwmon/tmp102.c | 9 +-------- > 1 file changed, 1 insertion(+), 8 deletions(-) > > diff --git a/drivers/hwmon/tmp102.c b/drivers/hwmon/tmp102.c > index 5eafbaada795..1af1932a72db 100644 > --- a/drivers/hwmon/tmp102.c > +++ b/drivers/hwmon/tmp102.c > @@ -268,14 +268,7 @@ static int tmp102_probe(struct i2c_client *client, > return err; > } > > - tmp102->ready_time = jiffies; > - if (tmp102->config_orig & TMP102_CONF_SD) { > - /* > - * Mark that we are not ready with data until the first > - * conversion is complete > - */ > - tmp102->ready_time += msecs_to_jiffies(CONVERSION_TIME_MS); > - } > + tmp102->ready_time = jiffies + msecs_to_jiffies(CONVERSION_TIME_MS); > > hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, > tmp102, Thanks for the quick fix. The change itself looks good but why remove the comment, which I think still retains its value? Reviewed-by: Jean Delvare <jdelvare@suse.de>
Hi Jean, On 10/24/2017 12:21 AM, Jean Delvare wrote: > Hi Guenter, > > On Mon, 23 Oct 2017 17:55:26 -0700, Guenter Roeck wrote: >> Commit 3d8f7a89a197 ("hwmon: (tmp102) Improve handling of initial read >> delay") reduced the initial temperature read delay and made it dependent >> on the chip's shutdown mode. If the chip was not in shutdown mode at probe, >> the read delay no longer applies. >> >> This ignores the fact that the chip initialization changes the temperature >> sensor resolution, and that the temperature register values change when >> the resolution is changed. As a result, the reported temperature is twice >> as high as the real temperature until the first temperature conversion >> after the configuration change is complete. This can result in unexpected >> behavior and, worst case, in a system shutdown. To fix the problem, >> let's just always wait for a conversion to complete before reporting >> a temperature. >> >> Fixes: 3d8f7a89a197 ("hwmon: (tmp102) Improve handling of initial read delay") >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=197167 >> Reported-by: Ralf Goebel <ralf.goebel@imago-technologies.com> >> Cc: Ralf Goebel <ralf.goebel@imago-technologies.com> >> Signed-off-by: Guenter Roeck <linux@roeck-us.net> >> --- >> drivers/hwmon/tmp102.c | 9 +-------- >> 1 file changed, 1 insertion(+), 8 deletions(-) >> >> diff --git a/drivers/hwmon/tmp102.c b/drivers/hwmon/tmp102.c >> index 5eafbaada795..1af1932a72db 100644 >> --- a/drivers/hwmon/tmp102.c >> +++ b/drivers/hwmon/tmp102.c >> @@ -268,14 +268,7 @@ static int tmp102_probe(struct i2c_client *client, >> return err; >> } >> >> - tmp102->ready_time = jiffies; >> - if (tmp102->config_orig & TMP102_CONF_SD) { >> - /* >> - * Mark that we are not ready with data until the first >> - * conversion is complete >> - */ >> - tmp102->ready_time += msecs_to_jiffies(CONVERSION_TIME_MS); >> - } >> + tmp102->ready_time = jiffies + msecs_to_jiffies(CONVERSION_TIME_MS); >> >> hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, >> tmp102, > > Thanks for the quick fix. The change itself looks good but why remove > the comment, which I think still retains its value? > Good point. I'll add it back in before sending the patch upstream. Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/hwmon/tmp102.c b/drivers/hwmon/tmp102.c index 5eafbaada795..1af1932a72db 100644 --- a/drivers/hwmon/tmp102.c +++ b/drivers/hwmon/tmp102.c @@ -268,14 +268,7 @@ static int tmp102_probe(struct i2c_client *client, return err; } - tmp102->ready_time = jiffies; - if (tmp102->config_orig & TMP102_CONF_SD) { - /* - * Mark that we are not ready with data until the first - * conversion is complete - */ - tmp102->ready_time += msecs_to_jiffies(CONVERSION_TIME_MS); - } + tmp102->ready_time = jiffies + msecs_to_jiffies(CONVERSION_TIME_MS); hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, tmp102,
Commit 3d8f7a89a197 ("hwmon: (tmp102) Improve handling of initial read delay") reduced the initial temperature read delay and made it dependent on the chip's shutdown mode. If the chip was not in shutdown mode at probe, the read delay no longer applies. This ignores the fact that the chip initialization changes the temperature sensor resolution, and that the temperature register values change when the resolution is changed. As a result, the reported temperature is twice as high as the real temperature until the first temperature conversion after the configuration change is complete. This can result in unexpected behavior and, worst case, in a system shutdown. To fix the problem, let's just always wait for a conversion to complete before reporting a temperature. Fixes: 3d8f7a89a197 ("hwmon: (tmp102) Improve handling of initial read delay") Link: https://bugzilla.kernel.org/show_bug.cgi?id=197167 Reported-by: Ralf Goebel <ralf.goebel@imago-technologies.com> Cc: Ralf Goebel <ralf.goebel@imago-technologies.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net> --- drivers/hwmon/tmp102.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-)