On 04/28/2016 03:23 AM, 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 ASL methods that that the BIOS can use to access
these fields. Most of the systems in question ASL 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 ASL 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 execute the read/write operation under
a lock which prevents ASL and OS from messing each other.
Tested-by: Andy Lutomirski <luto@xxxxxxxxxx> # Dell XPS 13 9350
This successfully works around:
https://bugzilla.kernel.org/show_bug.cgi?id=110041
but the BIOS people should still fix their ASL. Sigh.
On the Dell laptop, the observable effect is that the driver loads and
finds the iTCO thing.
Pali, this may be considerably more useful on your laptop.
--Andy
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