Hi Mika,
On Fri, 13 May 2016 15:45:55 +0300, 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-and-tested-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 v3:
>
> - Added Tested-by from Pali Rohár (The patch did not change that much so I
> though it is still valid)
> - Return -EBUSY instead of -EIO
> - Move dev_warns() to be inside if (!priv->acpi_reserved) block
> - Remove unnecessary variable "val"
> - Do not clear priv->acpi_reserved in i801_acpi_remove()
> - Return -ENODEV if we detect conflict
> - Call i801_acpi_remove() after i2c_del_adapter().
> (...)
Tested-by: Jean Delvare <jdelvare@xxxxxxx>
Reviewed-by: Jean Delvare <jdelvare@xxxxxxx>
Thanks,
--
Jean Delvare
SUSE L3 Support
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