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

["Pali Rohár" <pali.rohar@gmail.com>]

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On Friday 29 April 2016 20:10:23 Andy Lutomirski wrote:
> On Fri, Apr 29, 2016 at 2:03 AM, Pali Rohár <pali.rohar@gmail.com>
> wrote:
> > On Thursday 28 April 2016 11:34:38 Andy Lutomirski wrote:
> >> 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@kernel.org> # 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, I am right that I will be able to load i2c-i801.ko driver
> > without acpi_enforce_resources=lax parameter?
> 
> Yes, and it works on my laptop.

Looks like it is working also on my laptop.

> > If yes, then it sounds good! Finally I would be able to bind
> > lis3lv02d_i2c.ko driver for accelerometer which is on my E6440
> > machine.
> > 
> > Andy, is there any way to tell i2c-i801.ko driver that on i2c bus
> > (which that driver exports) is present some i2c device? Months ago
> > I got list of Latitude machines on which i2c address is that
> > accelerometer present.
> > 
> > It is possible to hardcode that mapping (DMI name of laptop --> i2c
> > address) into dell-laptop driver, so i2c-i801.ko and
> > lis3lv02d_i2c.ko will be automatically loaded and lis3l binded
> > correctly to i801 i2c address?
> 
> I don't know how this part works, but I doubt that doing it in
> dell-laptop will be convenient.  After all, dell-laptop can load
> before i2c-i801.
> 
> Jean and Wolfram: is there a quirk mechanism to add i2c devices that
> aren't directly enumerable but are known to exist due to DMI?

Maybe something like i2c_register_board_info()?

-- 
Pali Rohár
pali.rohar@gmail.com

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