Discrete GPU cannot be disabled in Yosemite

[skies457]

Hi all,

 

I'm using HP Envy 1220x with HD4000 and AMD HD8750M on board. I've managed to disable HD8750M in 10.9 by dsdt editing, but the same method does not working in 10.10. Here is my _OFF method exported from original SSDT:

Method (_OFF, 0, Serialized)
                {
                    \RMDT.P1 ("_OFF(): Discrete Graphics Card disabled.")
                    Store (LCTL, ELCT)
                    Store (SVID, HVID)
                    Store (SDID, HDID)
                    Store (One, LNKD)
                    While (LNotEqual (LNKS, Zero))
                    {
                        Sleep (One)
                    }

                    Store (0x02, AFES)
                    SGPO (HLRS, One)
                    SGPO (PWEN, Zero)
                    Notify (PEG0, Zero)
                    Return (Zero)
                }

And calls to _OFF method are added to _INI of _SB.PCI0, _INI of _SB.PCI0.PEG0.PEGP (where discrete GPU is located) and _WAK, but HD8750M still shows up in System Information:

 

Full DSDT and dmesg are included in attachments. Any help?

Thanks.

dsdt.zip

dmesg.log.zip