| Message ID | 20200903134704.8949-1-lars.povlsen@microchip.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | hwmon: sparx5: Fix initial reading of temperature | expand |
On 9/3/20 6:47 AM, Lars Povlsen wrote: > If the temperature is read before the internal calibration is > completed, the driver returns -EIO. Instead it should return -EAGAIN > to encourage repeating the operation. > > Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com> > --- > drivers/hwmon/sparx5-temp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/hwmon/sparx5-temp.c b/drivers/hwmon/sparx5-temp.c > index 1a2b1026b026..98be48e3a22a 100644 > --- a/drivers/hwmon/sparx5-temp.c > +++ b/drivers/hwmon/sparx5-temp.c > @@ -56,7 +56,7 @@ static int s5_read(struct device *dev, enum hwmon_sensor_types type, > case hwmon_temp_input: > stat = readl_relaxed(hwmon->base + TEMP_STAT); > if (!(stat & TEMP_STAT_VALID)) > - return -EIO; > + return -EAGAIN; The problem is that this may result in a hard loop and effectively hang the system, or at least the calling process. It may be better to return -ENODATA in this situation. Guenter > value = stat & TEMP_STAT_TEMP; > /* > * From register documentation: > -- > 2.27.0 >
Guenter Roeck writes: > On 9/3/20 6:47 AM, Lars Povlsen wrote: >> If the temperature is read before the internal calibration is >> completed, the driver returns -EIO. Instead it should return -EAGAIN >> to encourage repeating the operation. >> >> Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com> >> --- >> drivers/hwmon/sparx5-temp.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/hwmon/sparx5-temp.c b/drivers/hwmon/sparx5-temp.c >> index 1a2b1026b026..98be48e3a22a 100644 >> --- a/drivers/hwmon/sparx5-temp.c >> +++ b/drivers/hwmon/sparx5-temp.c >> @@ -56,7 +56,7 @@ static int s5_read(struct device *dev, enum hwmon_sensor_types type, >> case hwmon_temp_input: >> stat = readl_relaxed(hwmon->base + TEMP_STAT); >> if (!(stat & TEMP_STAT_VALID)) >> - return -EIO; >> + return -EAGAIN; > > The problem is that this may result in a hard loop and effectively hang the system, > or at least the calling process. It may be better to return -ENODATA in this situation. > Guenther, Thank you for your response. The motivation for the patch was as I tried to use thermal support to control a fan, and I noticed an initial quip from thermal_core.c:update_temperature() - it will throw a dev_warn() for anything else than an "EAGAIN". The EAGAIN also seems to be used by several other hwmon drivers in similar situations. The bottom line is that I would like to get rid of the warning message. Changing the error code to ENODATA does not fix what I am trying to accomplish. Do you have any suggestions on how to achieve the objective? Sincerely, ---Lars > Guenter > >> value = stat & TEMP_STAT_TEMP; >> /* >> * From register documentation: >> -- >> 2.27.0 >>
On 9/4/20 1:33 AM, Lars Povlsen wrote: > > Guenter Roeck writes: > >> On 9/3/20 6:47 AM, Lars Povlsen wrote: >>> If the temperature is read before the internal calibration is >>> completed, the driver returns -EIO. Instead it should return -EAGAIN >>> to encourage repeating the operation. >>> >>> Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com> >>> --- >>> drivers/hwmon/sparx5-temp.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/hwmon/sparx5-temp.c b/drivers/hwmon/sparx5-temp.c >>> index 1a2b1026b026..98be48e3a22a 100644 >>> --- a/drivers/hwmon/sparx5-temp.c >>> +++ b/drivers/hwmon/sparx5-temp.c >>> @@ -56,7 +56,7 @@ static int s5_read(struct device *dev, enum hwmon_sensor_types type, >>> case hwmon_temp_input: >>> stat = readl_relaxed(hwmon->base + TEMP_STAT); >>> if (!(stat & TEMP_STAT_VALID)) >>> - return -EIO; >>> + return -EAGAIN; >> >> The problem is that this may result in a hard loop and effectively hang the system, >> or at least the calling process. It may be better to return -ENODATA in this situation. >> > > Guenther, > > Thank you for your response. > > The motivation for the patch was as I tried to use thermal support to > control a fan, and I noticed an initial quip from > thermal_core.c:update_temperature() - it will throw a dev_warn() for > anything else than an "EAGAIN". The EAGAIN also seems to be used by > several other hwmon drivers in similar situations. > > The bottom line is that I would like to get rid of the warning > message. Changing the error code to ENODATA does not fix what I am > trying to accomplish. > Sigh. I know that -EAGAIN is used, but it has its own problems - userspace is inclined to retry directly, causing hard loops. Ok, lets go with -EAGAIN then. Can't be helped. I'll apply your patch. Guenter > Do you have any suggestions on how to achieve the objective? > > Sincerely, > > ---Lars > >> Guenter >> >>> value = stat & TEMP_STAT_TEMP; >>> /* >>> * From register documentation: >>> -- >>> 2.27.0 >>> >
On Thu, Sep 03, 2020 at 03:47:04PM +0200, Lars Povlsen wrote: > If the temperature is read before the internal calibration is > completed, the driver returns -EIO. Instead it should return -EAGAIN > to encourage repeating the operation. > > Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com> Applied. I added a note stating that I would prefer -ENODATA, and why, but that this is not feasible due to thermal subsystem requirements. Thanks, Guenter > --- > drivers/hwmon/sparx5-temp.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > -- > 2.27.0 > > diff --git a/drivers/hwmon/sparx5-temp.c b/drivers/hwmon/sparx5-temp.c > index 1a2b1026b026..98be48e3a22a 100644 > --- a/drivers/hwmon/sparx5-temp.c > +++ b/drivers/hwmon/sparx5-temp.c > @@ -56,7 +56,7 @@ static int s5_read(struct device *dev, enum hwmon_sensor_types type, > case hwmon_temp_input: > stat = readl_relaxed(hwmon->base + TEMP_STAT); > if (!(stat & TEMP_STAT_VALID)) > - return -EIO; > + return -EAGAIN; > value = stat & TEMP_STAT_TEMP; > /* > * From register documentation:
diff --git a/drivers/hwmon/sparx5-temp.c b/drivers/hwmon/sparx5-temp.c index 1a2b1026b026..98be48e3a22a 100644 --- a/drivers/hwmon/sparx5-temp.c +++ b/drivers/hwmon/sparx5-temp.c @@ -56,7 +56,7 @@ static int s5_read(struct device *dev, enum hwmon_sensor_types type, case hwmon_temp_input: stat = readl_relaxed(hwmon->base + TEMP_STAT); if (!(stat & TEMP_STAT_VALID)) - return -EIO; + return -EAGAIN; value = stat & TEMP_STAT_TEMP; /* * From register documentation:
If the temperature is read before the internal calibration is completed, the driver returns -EIO. Instead it should return -EAGAIN to encourage repeating the operation. Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com> --- drivers/hwmon/sparx5-temp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 2.27.0