Messages in this thread | | | Subject | Re: [regression] nct6775 does not load in 5.4 and 5.5, bisected to b84398d6d7f90080 | From | Guenter Roeck <> | Date | Sat, 22 Feb 2020 13:26:48 -0800 |
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On 2/22/20 12:49 PM, Martin Volf wrote: > Hello, > > On Sat, Feb 22, 2020 at 8:05 PM Guenter Roeck <linux@roeck-us.net> wrote: >> On 2/22/20 9:55 AM, Martin Volf wrote: >>> On Sat, Feb 22, 2020 at 4:41 PM Guenter Roeck <linux@roeck-us.net> wrote: >>>> On 2/22/20 3:13 AM, Martin Volf wrote: >>>>> 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. >>> ... >>>> My wild guess would be that the i801 driver is a bit aggressive with >>>> reserving memory spaces, but I don't immediately see what it does >>>> differently in that regard after the offending patch. Does it work >>>> if you unload the i2c_i801 driver first ? >>> >>> Yes, after unloading i2c_i801, the nct6775 works. > ... >>> This is diff of /proc/ioports in 5.3.18 with loaded nct6775 and in >>> 5.4.21 without: >>> >>> --- ioports-5.3.18 >>> +++ ioports-5.4.21 >>> @@ -2,6 +2,7 @@ >>> 0000-001f : dma1 >>> 0020-0021 : pic1 >>> 002e-0031 : iTCO_wdt >>> + 002e-0031 : iTCO_wdt >>> 0040-0043 : timer0 >>> 0050-0053 : timer1 > ... >>> So 0x2e is the resource the two drivers are fighting for. > ... >> Yes, and it should not do that, since the range can be used to access >> different segments of the same chip from multiple drivers. This region >> should only be reserved temporarily, using request_muxed_region() when >> needed and release_region() after the access is complete. Either case, >> I don't immediately see why that region would be interesting for the >> iTCO watchdog driver. >> >> Can you add some debugging into the i801 driver to see what memory regions >> it reserves, and how it gets to reserve 0x2e..0x31 ? That range really >> doesn't make any sense to me. > > in the function i801_add_tco() in drivers/i2c/busses/i2c-i801.c > (line 1601 in 5.4.21), there is this code: > > /* > * Power Management registers. > */ > devfn = PCI_DEVFN(PCI_SLOT(pci_dev->devfn), 2); > pci_bus_read_config_dword(pci_dev->bus, devfn, ACPIBASE, &base_addr); > > res = &tco_res[ICH_RES_IO_SMI]; > res->start = (base_addr & ~1) + ACPIBASE_SMI_OFF; > res->end = res->start + 3; > res->flags = IORESOURCE_IO; > > base_addr is 0xffffffff after pci_bus_read_config_dword() call. > ACPIBASE_SMI_OFF is 0x030, therefore res->start is 0x2e. > Not that I understand even a bit of this... >
Outch. This means that the code is broken. ACPIBASE is not configured, or disabled, or the code reads from the wrong PCI configuration register. What I don't understand is why this works with v5.3 kernels; the code looks just as bad there for me. I must be missing something. Either case, the only thing you can really do at this point is to blacklist the iTCO_wdt driver.
Other than that, we can only hope that someone who understands above code can provide a fix. Maybe Wolfram has an idea.
Guenter
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