Dealing with a sensor which doesn't have valid reading until host is powered up
james.feist at linux.intel.com
Sat Aug 29 03:54:02 AEST 2020
On 8/28/2020 9:43 AM, Alex Qiu wrote:
> Hi James,
> Thx for the reply! So right now, one thing is that the sensor is not
> dependent on the power state of the host solely, but also dependent on
> the boot progress of the host.
Would the BiosPost power state not suffice?
> And the more serious issue is that
> returning EAGAIN from the driver freezes the sensor, which is what I'm
> debugging right now. Do we have special treatment on errno returned by
> the driver? Thx.
I ran into a similar issue with the CPUSensor and this was my fix:
I haven't hit this issue with hwmon sensor though.
> - Alex Qiu
> On Fri, Aug 28, 2020 at 9:38 AM James Feist <james.feist at linux.intel.com
> <mailto:james.feist at linux.intel.com>> wrote:
> On 8/27/2020 2:49 PM, Alex Qiu wrote:
> > Hi James,
> > After some debugging, I realized that the code I pointed out earlier
> > wasn't the root cause. Update is that, the HwmonTempSensor stops
> > updating after the hwmon driver returns EAGAIN as errno. I'll keep
> > debugging...
> > - Alex Qiu
> > On Tue, Aug 25, 2020 at 5:49 PM Alex Qiu <xqiu at google.com
> <mailto:xqiu at google.com>
> > <mailto:xqiu at google.com <mailto:xqiu at google.com>>> wrote:
> > Hi James and OpenBMC community,
> > We have a sensor for HwmonTempSensor which doesn't have a valid
> > reading until the host is fully booted. Before it's becoming
> > and useful, it's getting disabled in code
> > because of errors thrown up by the hwmon driver. Ideally, the
> > thermal control loop should kick the fan to fail safe mode
> until no
> > more errors are observed.
> > Any suggestions on how we should handle this kind of sensor
> For what its worth we use the PowerState property that has options of
> power on or BiosPost to disable scanning when the state is invalid:
> > Thank you!
> > - Alex Qiu
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