On Thu, Jul 28, 2016 at 11:51:11AM +0200, Jean Delvare wrote:

Upstream commit: a7ae81952cdab56a1277bd2f9ed7284c0f575120

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@kernel.org>
Reported-by: Pali Roh�r <redacted>
Suggested-by: Rafael J. Wysocki <redacted>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Rafael J. Wysocki <redacted>
Reviewed-by: Jean Delvare <redacted>
Reviewed-by: Benjamin Tissoires <redacted>
Tested-by: Pali Roh�r <redacted>
Tested-by: Jean Delvare <redacted>
Signed-off-by: Wolfram Sang <redacted>
Cc: stable@vger.kernel.org
---
This is a backport of upstream commit
a7ae81952cdab56a1277bd2f9ed7284c0f575120 suitable for kernels v4.4 and
v4.6. Thanks.

Sorry for being non-responsive - I was on vacation and just came back.

Thanks Jean for taking care of backporting this.