[PATCH v4] pci: prevent putting nvidia GPUs into lower device states on certain intel bridges

[Karol Herbst]

for newer Windows the firmware uses bit  0x80 on 0x248 (Q0L2 being the
field name) on the bridge controller to turn of the device, on other
versions it uses the "older"? 0xb0 register and the P0LD field, which
is documented, where the former is not.

On Wed, Nov 20, 2019 at 12:51 PM Mika Westerberg
<mika.westerberg at intel.com> wrote:
>
> On Wed, Nov 20, 2019 at 01:22:16PM +0200, Mika Westerberg wrote:
> >             If (((OSYS <= 0x07D9) || ((OSYS == 0x07DF) && (_REV ==
> >                 0x05))))
> >             {
>
> The OSYS comes from this (in DSDT):
>
>                 If (_OSI ("Windows 2009"))
>                 {
>                     OSYS = 0x07D9
>                 }
>
>                 If (_OSI ("Windows 2012"))
>                 {
>                     OSYS = 0x07DC
>                 }
>
>                 If (_OSI ("Windows 2013"))
>                 {
>                     OSYS = 0x07DD
>                 }
>
>                 If (_OSI ("Windows 2015"))
>                 {
>                     OSYS = 0x07DF
>                 }
>
> So I guess this particular check tries to identify Windows 7 and older,
> and Linux.
>
> >                 If ((PIOF == Zero))
> >                 {
> >                     P0LD = One
> >                     TCNT = Zero
> >                     While ((TCNT < LDLY))
> >                     {
> >                         If ((P0LT == 0x08))
> >                         {
> >                             Break
> >                         }
> >
> >                         Sleep (0x10)
> >                         TCNT += 0x10
> >                     }
> >
> >                     P0RM = One
> >                     P0AP = 0x03
> >                 }
> >                 ElseIf ((PIOF == One))
> >                 {
> >                     P1LD = One
> >                     TCNT = Zero
> >                     While ((TCNT < LDLY))
> >                     {
> >                         If ((P1LT == 0x08))
> >                         {
> >                             Break
> >                         }
> >
> >                         Sleep (0x10)
> >                         TCNT += 0x10
> >                     }
> >
> >                     P1RM = One
> >                     P1AP = 0x03
> >                 }
> >                 ElseIf ((PIOF == 0x02))
> >                 {
> >                     P2LD = One
> >                     TCNT = Zero
> >                     While ((TCNT < LDLY))
> >                     {
> >                         If ((P2LT == 0x08))
> >                         {
> >                             Break
> >                         }
> >
> >                         Sleep (0x10)
> >                         TCNT += 0x10
> >                     }
> >
> >                     P2RM = One
> >                     P2AP = 0x03
> >                 }
> >
> >                 If ((PBGE != Zero))
> >                 {
> >                     If (SBDL (PIOF))
> >                     {
> >                         MBDL = GMXB (PIOF)
> >                         PDUB (PIOF, MBDL)
> >                     }
> >                 }
> >             }
> >             Else
> >             {
> >                 LKDS (PIOF)
> >             }
> >
> >             If ((DerefOf (SCLK [Zero]) != Zero))
> >             {
> >                 PCRO (0xDC, 0x100C, DerefOf (SCLK [One]))
> >                 Sleep (0x10)
> >             }
> >
> >             GPPR (PIOF, Zero)
> >             If ((OSYS != 0x07D9))
> >             {
> >                 DIWK (PIOF)
> >             }
> >
> >             \_SB.SGOV (0x01010004, Zero)
> >             Sleep (0x14)
> >             Return (Zero)
> >         }
>