FIX: Crash when using acpi_call with AMD discrete graphics card

Issue Description

Using acpi_call to disable and enable AMD discrete graphics card sometimes causes system to crash. Problem does not occur with a simple ‘disable card, enable card, run X’ test, but does sometimes occur if a period of time (in which the computer is used normally) is left before disabling and enabling the card.

Error Message

Upon running the X server, the computer crashes with a large wall of text, the first line of which being ‘Unable to handle NULL pointer dereference at 0000…034’ and many references to fglrx.

Cause of Issue

The cause of this issue is that before enabling the graphics card and running X, the computer has been suspended and un-suspended at least once while the discrete graphics card was disabled.

Solution

The solution to the issue is to ensure that the AMD graphics card is enabled before suspending. The card can then be disabled again after resuming and toggled normally.