Re: [PATCH v3] i2c: i801: Allow ACPI SystemIO OpRegion to conflict with PCI BAR

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On Monday 09 May 2016 10:17:14 Mika Westerberg wrote:
> Many Intel systems the BIOS declares a SystemIO OpRegion below the
> SMBus PCI device as can be seen in ACPI DSDT table from Lenovo Yoga
> 900:
> 
>   Device (SBUS)
>   {
>       OperationRegion (SMBI, SystemIO, (SBAR << 0x05), 0x10)
>       Field (SMBI, ByteAcc, NoLock, Preserve)
>       {
>           HSTS,   8,
>           Offset (0x02),
>           HCON,   8,
>           HCOM,   8,
>           TXSA,   8,
>           DAT0,   8,
>           DAT1,   8,
>           HBDR,   8,
>           PECR,   8,
>           RXSA,   8,
>           SDAT,   16
>       }
> 
> There are also bunch of AML methods that that the BIOS can use to
> access these fields. Most of the systems in question AML methods
> accessing the SMBI OpRegion are never used.
> 
> Now, because of this SMBI OpRegion many systems fail to load the
> SMBus driver with an error looking like one below:
> 
>   ACPI Warning: SystemIO range 0x0000000000003040-0x000000000000305F
>        conflicts with OpRegion 0x0000000000003040-0x000000000000304F
>        (\_SB.PCI0.SBUS.SMBI) (20160108/utaddress-255)
>   ACPI: If an ACPI driver is available for this device, you should
> use it instead of the native driver
> 
> The reason is that this SMBI OpRegion conflicts with the PCI BAR used
> by the SMBus driver.
> 
> It turns out that we can install a custom SystemIO address space
> handler for the SMBus device to intercept all accesses through that
> OpRegion. This allows us to share the PCI BAR with the AML code if
> it for some reason is using it. We do not expect that this OpRegion
> handler will ever be called but if it is we print a warning and
> prevent all access from the SMBus driver itself.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=110041
> Reported-by: Andy Lutomirski <luto@xxxxxxxxxx>
> Reported-by: Pali Rohár <pali.rohar@xxxxxxxxx>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> Changes to v2:
> 
>  - Return -EIO instead of -EPERM
>  - Added ACK from Rafael
>  - Added Link and Reported-by tags
>  - Tagged for stable inclusion

Working fine on my Latitude E6440, add my:

Tested-By: Pali Rohár <pali.rohar@xxxxxxxxx>

-- 
Pali Rohár
pali.rohar@xxxxxxxxx

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