Reported temperature of nvidia card with nouveau driver is wrong

Submitted by Jirka Novak

Assigned to Nouveau Project

Link to original bug (#107325)

Description

Hello,

I use Dell Precision 3530 with NVIDIA Corporation GP107GLM [Quadro P600 Mobile] (rev a1). I use Fedora Core 28 with 4.17.6 x86_64 kernel.
I found that sensors tool shows wrong temperature:

$ sensors
nouveau-pci-0100
Adapter: PCI adapter
temp1: +511.0°C (high = +95.0°C, hyst = +3.0°C)
(crit = +105.0°C, hyst = +5.0°C)
(emerg = +135.0°C, hyst = +5.0°C)

Temperature is obviously wrong.
I tried to troubleshoot it on sensors side and it looks that sensors tool receives this wrong value from driver.
I made one more observation - right after suspend/wakeup the value is completely different:

$ sensors
nouveau-pci-0100
Adapter: PCI adapter
temp1: +511.0°C (high = +95.0°C, hyst = +3.0°C)
(crit = +105.0°C, hyst = +5.0°C)
(emerg = +135.0°C, hyst = +5.0°C)

$ sensors
nouveau-pci-0100
Adapter: PCI adapter
temp1: +43.0°C (high = +95.0°C, hyst = +3.0°C)
(crit = +105.0°C, hyst = +5.0°C)
(emerg = +135.0°C, hyst = +5.0°C)

$ sensors
nouveau-pci-0100
Adapter: PCI adapter
temp1: +511.0°C (high = +95.0°C, hyst = +3.0°C)
(crit = +105.0°C, hyst = +5.0°C)
(emerg = +135.0°C, hyst = +5.0°C)

I can provide more information when required.