On 26.05.2017 23:03, Lukas Wunner wrote: > On Fri, May 26, 2017 at 02:13:29PM +0200, Florian Echtler wrote: >> I'm running Ubuntu 16.04.2 on a 27" unibody iMac 10,1 from 2009. However, even >> with the most recent HWE stack (kernel 4.8), the display stays black after >> suspend. I can ssh into the machine, so wakeup is OK, but the display is >> entirely black (backlight stays off). >> > The ATI card has MXM_PNL_PWR_EN and MXM_PNL_BL_EN pins. Those must be > enabled for the panel to light up. Perhaps radeon needs to be extended > to do that. One theory is that this is done via ACPI, but perhaps > only if a certain operating system is running. Dump the ACPI tables > and search DSDT and SSDT* tables for methods relating to the ATI card > and/or backlight. If you find checks for OSDW there (e.g. in _PS0, > i.e. on resume), it means the AML code is only executed on Darwin. I've already had a look at the ACPI tables; there seem to be no references to the "official" backlight/display control functions (no _BL? or _DO? methods). > Conversely !OSDW means the code is only executed on Windows (Boot Camp). > Linux masquerades as Darwin, but this can be disabled with > acpi_osi=!Darwin on the command line. It's worth trying if that changes > the behaviour. If it does, then macOS likely sets those pins on resume > and we need to do the same in radeon. There are OSDW checks present, however, booting with acpi_osi=!Darwin doesn't make a difference to the backlight behaviour. I'd be grateful for other suggestions... Best regards, Florian -- SENT FROM MY DEC VT50 TERMINAL
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