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    SubjectRe: [PATCH] apple-gmux: Restore switch registers on suspend/resume
    On Tue, Jul 10, 2012 at 09:09:53AM +0530, Arun Raghavan wrote:
    > After suspend and resume, the values of these registers seem to change
    > from what they were at suspend time, potentially preventing the actual
    > output lines from being enabled post-resume. This saves relevant state
    > at suspend and restores it when resumed.
    > This is at least required on the MacBook Pro 8.2 when the Intel GPU is
    > manually selected in GRUB config before the kernel is loaded.

    I've got a couple of problems with this. The first is that the backlight
    update_status callback isn't an appropriate place to do this. Adding
    suspend/resume ops for the pnp_driver would be better.

    But the more serious concern is whether or not its safe to simply
    restore the register values. I know that the reverse engineering work
    done on the gmux has revealed a particular sequence for selecting the
    active GPU. A brute force restoration of the registers disregards this
    sequencing, which doesn't seem like a good idea.


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