Re: [v5] i2c: i801: Allow ACPI SystemIO OpRegion to conflict with PCI BAR

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Tue, Jul 05, 2016 at 01:30:23PM +0200, Pali Rohár wrote:
> On Tuesday 05 July 2016 12:14:55 Mika Westerberg wrote:
> > The whole point of this patch is that we expect that nobody never
> > uses that OpRegion. I'm 99% sure you don't find a single machine
> > where it is actually in use.
> 
> HP EliteBook 8460p uses it for sure! Here are DSDT snips:
> 
> 
>                 Method (\_SB.PCI0.LPCB.SMAB, 3, Serialized)
>                 {
>                     If (LEqual (And (Arg0, 0x01), 0x00))
>                     {
>                         Store (0x01, Local0)
>                         Store (\_SB.PCI0.SBUS.SWRB (Arg0, Arg1, Arg2), Local1)
>                         If (Local1)
>                         {
>                             Store (0x00, Local0)
>                         }
>                     }
>                     Else
>                     {
>                         Store (\_SB.PCI0.SBUS.SRDB (Arg0, Arg1), Local0)
>                     }
> 
>                     Return (Local0)
>                 }
> 

Crap, well that is in that 1% then ;-)

> ...
> 
>                 Method (ALRD, 1, Serialized)
>                 {
>                     Store (\_SB.PCI0.LPCB.SMAB (0x33, Arg0, 0x00), Local0)
>                     Return (Local0)
>                 }
> 
>                 Method (ALWR, 2, Serialized)
>                 {
>                     Store (\_SB.PCI0.LPCB.SMAB (0x32, Arg0, Arg1), Local0)
>                     Return (Local0)
>                 }
> 
> 
> And ALRD and ALWR methods are used by hp_accel.ko kernel driver.

So are you able to test what happens when you unload the driver? I think
the safest thing to do is that we just pin the driver in the kernel once
we notice the OpRegion is being accessed. Does anyone else have better
ideas?
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