Rafael J. Wysocki wrote:
From: Rafael J. Wysocki <rjw@xxxxxxx> Subject: ACPI suspend: Blacklist boxes that require us to set SCI_EN directly on resume Some Apple boxes evidently require us to set SCI_EN on resume directly, because if we don't do that, they hung somewhere in the resume code path. Moreover, on these boxes it is not sufficient to use acpi_enable() to turn ACPI on during resume. All of this is against the ACPI specification which states that (1) the BIOS is supposed to return from the S3 sleep state with ACPI enabled (SCI_EN set) and (2) the SCI_EN bit is owned by the hardware and we are not supposed to change it. For this reason, blacklist the affected systems so that the SCI_EN bit is set during resume on them. [NOTE: Unconditional setting SCI_EN for all system on resume doesn't work, because it makes some other systems crash (that's to be expected). Also, it is not entirely clear right now if all of the Apple boxes require this workaround.]
This is rather gross. The usual question arises, why does Windows work without such a hack? Maybe there is no better solution for now, but somebody should really look into why the behavior is different in Linux..
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