Re: [regression] nct6775 does not load in 5.4 and 5.5, bisected to b84398d6d7f90080

[Wolfram Sang]

Hi Martin,

On Sat, Feb 22, 2020 at 12:13:07PM +0100, Martin Volf wrote:
> Hello,
> 
> hardware monitoring sensors NCT6796D on my Asus PRIME Z390M-PLUS
> motherboard with Intel i7-9700 CPU don't work with 5.4 and newer linux
> kernels, the driver nct6775 does not load.
> 
> It is working OK in version 5.3. I have used almost all released stable
> versions from 5.3.8 to 5.3.16; I didn't try older kernels.
> 
> Even on new kernels the sensors-detect finds the sensors:
>         Found `Nuvoton NCT6796D Super IO Sensors' Success!
>             (address 0x290, driver `nct6775')
> but "modprobe nct6775" says:
>         ERROR: could not insert 'nct6775': No such device
> There is nothing interesting in dmesg.
> 
> git bisect found out the first bad commit is
> b84398d6d7f900805662b1619223fd644d862d7c,
> i2c: i801: Use iTCO version 6 in Cannon Lake PCH and beyond
> 
> Unfortunately I am not able to revert it in v5.4 to confirm it is really
> the culprit.
> 
> Is there a way to have working hwmon sensors on my system in newer linux
> kernels?

Well, it worked before, so I am quite sure it can be fixed. Thank you
very much for your detailed regression report! Sadly, I am not familiar
enough with those drivers, but you put the right people on CC, so I
think you will get more feedback within the next days. I'll keep an eye
on this, too.

Happy hacking,

   Wolfram

> 
> Thanks,
> 
> Martin
> 
> --8<--
> lspci
> 00:00.0 Host bridge: Intel Corporation 8th Gen Core 8-core Desktop
> Processor Host Bridge/DRAM Registers [Coffee Lake S] (rev 0d)
> 00:02.0 VGA compatible controller: Intel Corporation UHD Graphics 630
> (Desktop 9 Series) (rev 02)
> 00:14.0 USB controller: Intel Corporation Cannon Lake PCH USB 3.1 xHCI
> Host Controller (rev 10)
> 00:14.2 RAM memory: Intel Corporation Cannon Lake PCH Shared SRAM (rev 10)
> 00:16.0 Communication controller: Intel Corporation Cannon Lake PCH
> HECI Controller (rev 10)
> 00:17.0 SATA controller: Intel Corporation Cannon Lake PCH SATA AHCI
> Controller (rev 10)
> 00:1b.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root
> Port #17 (rev f0)
> 00:1c.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root
> Port #1 (rev f0)
> 00:1c.6 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root
> Port #7 (rev f0)
> 00:1d.0 PCI bridge: Intel Corporation Cannon Lake PCH PCI Express Root
> Port #9 (rev f0)
> 00:1f.0 ISA bridge: Intel Corporation Z390 Chipset LPC/eSPI Controller (rev 10)
> 00:1f.3 Audio device: Intel Corporation Cannon Lake PCH cAVS (rev 10)
> 00:1f.4 SMBus: Intel Corporation Cannon Lake PCH SMBus Controller (rev 10)
> 00:1f.5 Serial bus controller [0c80]: Intel Corporation Cannon Lake
> PCH SPI Controller (rev 10)
> 00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (7)
> I219-V (rev 10)

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