Re: [lm-sensors] [PATCH 9/9] hwmon: (it87) Report thermal sensor type as Intel PECI if appropriate

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Nov 01, 2012 at 07:12:08PM +0100, Jean Delvare wrote:
> On Thu, 1 Nov 2012 10:17:07 -0700, Guenter Roeck wrote:
> > On Thu, Nov 01, 2012 at 05:37:57PM +0100, Jean Delvare wrote:
> > > On an IT8720F chip with temp3 configured for PECI:
> > > 
> > > temp1_offset: 0
> > > temp2_offset: 0
> > > temp3_offset: -128000
> > > 
> > > I'm unsure how to interpret this -128000... This value is definitely
> > > not neutral, doesn't sound very realistic. I would expect a positive
> > > number for PECI. Maybe the offset register should be treated as
> > > unsigned in PECI mode? Or maybe its value is irrelevant for the IT8720F
> > > in PECI mode.
> > > 
> > > # grep . /sys/class/hwmon/hwmon2/device/temp3*
> > > /sys/class/hwmon/hwmon2/device/temp3_alarm:0
> > > /sys/class/hwmon/hwmon2/device/temp3_beep:1
> > > /sys/class/hwmon/hwmon2/device/temp3_input:25000
> > > /sys/class/hwmon/hwmon2/device/temp3_max:70000
> > > /sys/class/hwmon/hwmon2/device/temp3_min:127000
> > > /sys/class/hwmon/hwmon2/device/temp3_offset:-128000
> > > /sys/class/hwmon/hwmon2/device/temp3_type:6
> > > 
> > > This is with an it87 driver including all your recent patches. It you
> > > have ideas or theories, I'm interested.
> > > 
> > Hi Jean,
> > 
> > I agree. The alternative (+128 degrees C) sounds a bit high, though.
> > Maybe there is another register on IT8720F to store Tjmax ? Did you check
> > in the register map if there is a register value that happens to match it ?
> 
> How would I know which value I am looking for? k10temp says this:
> high = +70.0°C, crit = +90.0°C, hyst = +87.0°C
> but the monitored value doesn't match it87's temp3.
> 
> > What happens if you change the offset register value to, say, 100 ?
> > Does the reported temperature change as well ?
> 
> Yes it does.
> temp3_offset =  120000 -> temp3_input = 14000
> temp3_offset =  125000 -> temp3_input = 19000
> temp3_offset = -128000 -> temp3_input = 22000
> temp3_offset = -126000 -> temp3_input = 23000
> 
> This leads me to the conclusion that the offset registers are unsigned
> in PECI mode.
> 
If so, then only for AMD, or it is is a chip dependent.

On Intel (with IT8728F):

temp3_offset = -20000:	temp3_input = -96000
temp3_offset = -10000:	temp3_input = -87000
temp3_offset = 0:	temp3_input = -76000
temp3_offset = 10000:	temp3_input = -67000
temp3_offset = 20000:	temp3_input = -56000
temp3_offset = 105000:	temp3_input = 28000 (matches Tjmax / coretemp)

I don't know what AMD uses as equivalent of Tjmax - maybe they
use a fixed value of 128°C.

> > Another maybe dumb question - is this with Intel or AMD CPU ? Because
> > if it is AMD, it would not be PECI but AMDSI (something to fix if someone
> > has a system w/ IT87xx and AMD CPU).
> 
> It is AMD indeed, that's another issue I wanted to report. Do you
> already know how to fix it?
> 
Yes, I think so, at least I have an idea. Give me a couple of days.

Guenter

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