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

[Martin Volf]

On Mon, Feb 24, 2020 at 12:27 PM Mika Westerberg
<mika.westerberg@xxxxxxxxxxxxxxx> wrote:
>
> On Mon, Feb 24, 2020 at 12:51:25PM +0200, Mika Westerberg wrote:
> > > I'm wondering if
> > >
> > >             pci_dev_is_present(...);
> > >
> > > returns false here.
> >
> > Well that might also be the case since lspci shows this:
> >
> > 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)
> >
> > PMC is 1f.2 and not present here. However, it may be that the PMC is
> > still there it just does not "enumerate" because its devid/vendorid are
> > set to 0xffff. Similar hiding was done for the P2SB bridge.
>
> Actually I think this is the case here.
>
> I don't know the iTCO_wdt well enough to say if it could live without
> the ICH_RES_IO_SMI. It looks like this register is used to disable SMI
> generation but not sure how well it works if it is left to BIOS to
> configure. I suppose these systems should use WDAT instead.
>
> Martin, can you try the below patch?
>
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index ba87305f4332..c16e5ad08641 100644
> --- a/drivers/i2c/busses/i2c-i801.c
> +++ b/drivers/i2c/busses/i2c-i801.c
> @@ -1593,7 +1593,7 @@ i801_add_tco_cnl(struct i801_priv *priv, struct pci_dev *pci_dev,
>  static void i801_add_tco(struct i801_priv *priv)
>  {
>         u32 base_addr, tco_base, tco_ctl, ctrl_val;
> -       struct pci_dev *pci_dev = priv->pci_dev;
> +       struct pci_dev *pmc_dev, *pci_dev = priv->pci_dev;
>         struct resource tco_res[3], *res;
>         unsigned int devfn;
>
> @@ -1620,7 +1620,12 @@ static void i801_add_tco(struct i801_priv *priv)
>          * Power Management registers.
>          */
>         devfn = PCI_DEVFN(PCI_SLOT(pci_dev->devfn), 2);
> -       pci_bus_read_config_dword(pci_dev->bus, devfn, ACPIBASE, &base_addr);
> +       pmc_dev = pci_get_slot(pci_dev->bus, devfn);
> +       if (!pmc_dev) {
> +               dev_info(&pci_dev->dev, "PMC device disabled, not enabling iTCO\n");
> +               return;
> +       }
> +       pci_read_config_dword(pmc_dev, ACPIBASE, &base_addr);
>
>         res = &tco_res[ICH_RES_IO_SMI];
>         res->start = (base_addr & ~1) + ACPIBASE_SMI_OFF;
> @@ -1630,15 +1635,17 @@ static void i801_add_tco(struct i801_priv *priv)
>         /*
>          * Enable the ACPI I/O space.
>          */
> -       pci_bus_read_config_dword(pci_dev->bus, devfn, ACPICTRL, &ctrl_val);
> +       pci_read_config_dword(pmc_dev, ACPICTRL, &ctrl_val);
>         ctrl_val |= ACPICTRL_EN;
> -       pci_bus_write_config_dword(pci_dev->bus, devfn, ACPICTRL, ctrl_val);
> +       pci_write_config_dword(pmc_dev, ACPICTRL, ctrl_val);
>
>         if (priv->features & FEATURE_TCO_CNL)
>                 priv->tco_pdev = i801_add_tco_cnl(priv, pci_dev, tco_res);
>         else
>                 priv->tco_pdev = i801_add_tco_spt(priv, pci_dev, tco_res);
>
> +       pci_dev_put(pmc_dev);
> +
>         if (IS_ERR(priv->tco_pdev))
>                 dev_warn(&pci_dev->dev, "failed to create iTCO device\n");
>  }

Hello,

with the patch applied, the sensors are working, dmesg says:
...
[    2.804423] i801_smbus 0000:00:1f.4: SPD Write Disable is set
[    2.804478] i801_smbus 0000:00:1f.4: SMBus using PCI interrupt
[    2.804491] i801_smbus 0000:00:1f.4: PMC device disabled, not enabling iTCO
...
[    2.826373] nct6775: Enabling hardware monitor logical device mappings.
[    2.826447] nct6775: Found NCT6798D or compatible chip at 0x2e:0x290
...

and there is no "002e-0031" line in /proc/ioports.

Martin