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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