[Intel-gfx] BUG: resume from standby on 830GM broken

[Thomas Richter]

Dear intel-gfx developers,

suspend from standby is broken on the Fujitsu-Siemens Lifebook S2474, at 
least from kernel 3.4 up to 3.10.9.  The hardware is a 00:02.0 VGA 
compatible controller: Intel Corporation 82830M/MG Integrated Graphics 
Controller (rev 04), i.e. a 830GM. The machine suspends correctly, but 
resume from RAM does not proceed and the display remains dark. 
Activating the resume debug mode of the kernel that uses the RTC to 
store state information confirms that the kernel locks up on the PCI 
device 00:02.0.

The problem might be related to the NS2501 DVO. The problem is here that 
the ns2501 locks up and does not react on the i2c bus unless the output 
pipelines are configured correctly.

I believe in an early version of the patch I provided to support the 
ns2501, the
enable_dvo() function included a specific hack to force enable the dvo, 
by calling into a private function of the i915 module. I seem to 
remember that with this specific hack enabled, resume did work (at least 
most of the time), so something is not yet quite right when configuring 
the dvo.

Greetings,
     Thomas