Message-ID: <20201001221023.GA12766@pendragon.ideasonboard.com>
Date:   Fri, 2 Oct 2020 01:10:23 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     Ben Gamari <ben@...rt-cactus.org>, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@....fi>
Subject: Re: OpRegion conflicts for Skylake LPSS

Hi Mika,

Reviving an old thread.

On Mon, May 02, 2016 at 01:35:01PM +0300, Mika Westerberg wrote:
> On Sun, May 01, 2016 at 12:47:58AM +0200, Ben Gamari wrote:
> > Mika Westerberg <mika.westerberg@...ux.intel.com> writes:
> > > On Fri, Apr 29, 2016 at 09:30:27AM +0200, Ben Gamari wrote:
> > >> Ben Gamari <ben@...rt-cactus.org> writes:
> > >> 
> > >> > [ Unknown signature status ]
> > >> > Mika Westerberg <mika.westerberg@...ux.intel.com> writes:
> > >> >
> > >> >> On Tue, Apr 26, 2016 at 02:44:13AM +0200, Ben Gamari wrote:
> > >> >>> 
> > >> > snip
> > >> >
> > >> >>> It looks very much like these are describing the same device. Perhaps
> > >> >>> the lpss driver should be binding to this ACPI node? Or perhaps this is
> > >> >>> a firmware issue? Any guidance would be greatly appreciated.
> > >> >>
> > >> >> Can you send me full acpidump of that machine?
> > >> >
> > >> > It can be found at
> > >> > https://github.com/bgamari/dell-e7470-dsdt/blob/master/acpi.log.
> > >> >
> > >> Did this provide any insight? Let me know if more information would be
> > >> helpful.
> > >
> > > Sorry about the delay.
> >
> > No worries.
> > 
> > > The GEXP device is most probably a GPIO expander that is connected to
> > > one of the I2C buses. And it indeed looks to use directly the I2C host
> > > controller registers so kernel rightfully complains about that.
> > >
> > > Are you able to run Windows on that machine? If yes, it would be nice to
> > > know if the INT3446 I2C device is shown in the device manager.
> >
> > I had the original SSD that came with the machine with the original
> > Windows 7 installation intact. I popped it in and found no such device.
> > I then updated to Windows 10 (albeit still booting with the legacy BIOS,
> > not EFI) and found that once again there is no such device shown in
> > device manager.
> 
> That's what I would expect. ACPI spec says that if there is an OpRegion
> touching the same registers than PCI device the OS should not load any
> driver for that device. I guess this is exactly what Windows does.
> 
> Linux does it also but it in addition it issues a scary warning which
> might get users thinking there is something wrong with their system.

I'm trying to get camera sensors detected on a Microsoft Surface Go 2
machine (ACPI dumps available at
https://github.com/linux-surface/acpidumps/tree/master/surface_go_2).
The CPU is an Intel Pentium Gold 4425Y, based on Kaby Lake-Y. The DSDT
has been carefully designed, with great care to make it as useless as
possible, so I'm experiencing a few issues.

One of the camera sensors is connected to I2C4, backed by an LPSS I2C
controller.

00:19.2 Signal processing controller: Intel Corporation Sunrise Point-LP Serial IO I2C Controller #4 (rev 21)
        Subsystem: QUANTA Computer Inc Sunrise Point-LP Serial IO I2C Controller
        Flags: fast devsel, IRQ 34
        Memory at b1648000 (64-bit, non-prefetchable) [size=4K]
        Capabilities: [80] Power Management version 3
        Capabilities: [90] Vendor Specific Information: Len=14 <?>
        Kernel modules: intel_lpss_pci

Unfortunately the driver fails to probe due to the same issue reported
by Ben:

[    2.060237] intel-lpss 0000:00:19.2: enabling device (0000 -> 0002)
[    2.060483] ACPI Warning: SystemMemory range 0x00000000B1648000-0x00000000B16481FF conflicts with OpRegion 0x00000000B1648000-0x00000000B1648207 (\_SB.PCI0.GEXP.BAR0) (20200528/utaddress-213)
[    2.060489] ACPI: If an ACPI driver is available for this device, you should use it instead of the native driver
[    2.060726] intel-lpss: probe of 0000:00:19.2 failed with error -16

I've checked the GEXP device in the DSDT, and it includes an LPSS I2C
host controller driver in AML, using an OpRegion that covers the I2C
controller registers.

Adding acpi_enforce_resources=lax to the kernel command line allows the
I2C controller to be probed, but that's hardly a good solution, as two
drivers (one in the DSDT, one in the kernel) that poke the same hardware
is calling for trouble.

I've noticed that Windows maps the devices to different addresses than
Linux. On Windows, the I2C controllers are at

I2C0 (8086:9d60): 0xfe40f000 - 0xfe40ffff (IRQ 16)
I2C1 (8086:9d61): 0xfe40e000 - 0xfe40efff (IRQ 17)
I2C2 (8086:96d2): 0xfe40d000 - 0xfe40dfff (IRQ 18)
I2C3 (8086:96d3): 0xfe40c000 - 0xfe40cfff (IRQ 19)
I2C4 (8086:96d4): 0xfe409000 - 0xfe409fff (IRQ 34)

while on Linux they're at

I2C0 (8086:9d60): 0xb1642000 - 0xb1642fff (IRQ 16)
I2C1 (8086:9d61): 0xb1643000 - 0xb1643fff (IRQ 17)
I2C2 (8086:96d2): 0xb1644000 - 0xb1644fff (IRQ 18)
I2C3 (8086:96d3): 0xb1645000 - 0xb1645fff (IRQ 19)
I2C4 (8086:96d4): 0xb1648000 - 0xb1648fff (IRQ 34)

Interestingly, the I2C4 object contains the following in the DSDT:

            If ((SMD4 != 0x02))
            {
                Name (_HID, "INT3446")  // _HID: Hardware ID
                Method (_HRV, 0, NotSerialized)  // _HRV: Hardware Revision
                {
                    Return (LHRV (SB14))
                }

                Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
                {
                    Return (LCRS (SMD4, SB04, SIR4))
                }

                Method (_STA, 0, NotSerialized)  // _STA: Status
                {
                    Return (LSTA (SMD4))
                }
            }

            If ((SMD4 == 0x02))
            {
                Name (_ADR, 0x00190002)  // _ADR: Address
                Method (_DSM, 4, Serialized)  // _DSM: Device-Specific Method
                {
                    If (PCIC (Arg0))
                    {
                        Return (PCID (Arg0, Arg1, Arg2, Arg3))
                    }

                    Return (Buffer (One)
                    {
                         0x00                                             // .
                    })
                }
            }

I've evaluated SMD4 with acpidbg and it's equal to 2. I thought it might
be set to a different value in windows, but the hardware IDs reported by
the device manager all refer to the PCI device, not the ACPI device, so
I don't think that's a lead.

I really wonder how this is supposed to be handled, would the device
really be designed to work in such an unsafe way ? Does Windows remap
the BAR due to the conflict with the GEXP, rendering the GEXP
non-operational after boot ? I have tried to locate the GEXP in the
device manager in Windows, but with its _STA method returning 0x0b, it
seems not to be visible.

> > >> Also, is there a way to simply allow the driver subsystem to allow
> > >> probing to proceed despite this resource conflict so that I can resume
> > >> debugging my original input device issue?
> > >
> > > Try to pass "acpi_enforce_resources=lax" in the kernel command line.
> > 
> > Thanks, indeed this allows the driver to load. Unfortunately it didn't
> > take long to encounter further issues.
> > 
> > The motivation for all of this is to get the touchpad into I2C mode, since
> > currently it is merely exposed as a simple PS/2 device. Unfortunately it
> > seems that even Windows 10 doesn't use the touchpad's I2C mode (although
> > I suppose it's possible that this is guarded on UEFI boot; moreover
> > Windows appears to have proper support for configurating this touchpad
> > in PS/2 mode, which is unfortunately an ALPS devices).
> > 
> > Looking at the DSDT it seems that enabling the I2C interface may require
> > the help of the embedded controller, the state of which is exposed in
> > the DSDT through a mysteriously-named SDS1 field. It looks like this
> > field could take on a number of values which identify a variety of
> > different touchpads. Given that it looks like GPIO pin states may be
> > determined by the value of this field I'm a bit reluctant to go fiddling
> > around with it. 
> > 
> > I do wish that firmware weren't such a nightmare.
> 
> +1

-- 
Regards,

Laurent Pinchart

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