From: Guenter Roeck <linux@roeck-us.net>
To: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Martin Volf <martin.volf.42@gmail.com>,
Jean Delvare <jdelvare@suse.com>,
Wolfram Sang <wsa@the-dreams.de>,
linux-i2c@vger.kernel.org, linux-hwmon@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Jarkko Nikula <jarkko.nikula@linux.intel.com>
Subject: Re: [regression] nct6775 does not load in 5.4 and 5.5, bisected to b84398d6d7f90080
Date: Mon, 24 Feb 2020 10:27:30 -0800 [thread overview]
Message-ID: <20200224182730.GA29799@roeck-us.net> (raw)
In-Reply-To: <20200224112740.GL2667@lahna.fi.intel.com>
On Mon, Feb 24, 2020 at 01:27:40PM +0200, Mika Westerberg 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.
>
In practice the region is only used if
if (turn_SMI_watchdog_clear_off >= p->iTCO_version) {
where turn_SMI_watchdog_clear_off is 1 by default. It is also
passed to vendor specific code, but that is only relevant for
really old systems. In short, it isn't really needed for any
recent-generation systems, and could be made optional with
a few lines of code in iTCO_wdt.c.
Guenter
next prev parent reply other threads:[~2020-02-24 18:27 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-22 11:13 [regression] nct6775 does not load in 5.4 and 5.5, bisected to b84398d6d7f90080 Martin Volf
2020-02-22 11:51 ` Wolfram Sang
2020-02-22 15:41 ` Guenter Roeck
2020-02-22 17:55 ` Martin Volf
2020-02-22 19:05 ` Guenter Roeck
2020-02-22 20:49 ` Martin Volf
2020-02-22 21:26 ` Guenter Roeck
2020-02-23 7:06 ` Martin Volf
2020-02-23 16:39 ` Wolfram Sang
2020-02-24 10:18 ` Mika Westerberg
2020-02-24 10:37 ` Andy Shevchenko
2020-02-24 10:51 ` Mika Westerberg
2020-02-24 11:27 ` Mika Westerberg
2020-02-24 17:30 ` Martin Volf
2020-02-25 12:13 ` Mika Westerberg
2020-02-24 18:27 ` Guenter Roeck [this message]
2020-02-25 12:14 ` Mika Westerberg
2020-02-23 17:56 ` Gabriel C
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