Messages in this thread |  | | | Subject | Re: [RFC] Reliable video POSTing on resume (was: Re: [ACPI] Samsung P35, S3, black screen (radeon)) | | From | (Eric W. Biederman) | | Date | 07 Feb 2005 12:27:41 -0700 |
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Pavel Machek <pavel@ucw.cz> writes:
> Hi! > > > > We already try to do that, but it hangs on 70% of machines. See > > > Documentation/power/video.txt. > > > > We know that all of these ROMs are run at power on so they have to > > work. This implies that there must be something wrong with the > > environment the ROM are being run in. Video ROMs make calls into the > > INT vectors of the system BIOS. If these haven't been set up yet > > running the VBIOS is sure to hang. Has someone with ROM source and > > the appropriate debugging tools tried to debug one of these hangs? > > Alternatively code could be added to wakeup.S to try and set these up > > or dump the ones that are there and see if they are sane. > > Rumors say that notebooks no longer have video bios at C000h:0; rumors > say that video BIOS on notebooks is simply integrated into main system > BIOS. I personaly do not know if rumors are true, but PCs are ugly > machines....
The state of current hardware has already been mentioned but let me clarify. This is not a laptop problem anytime you have onboard video you are unlikely to have a separate video ROM. This includes many recent server boards as well as laptops. When the board boots up there will be a video option ROM shadowed into the usually location at C000h:0 but what becomes of it afterwards is a good question.
For server boards most commonly this seems to be a flavor of the ATI Rage XL chip. It is a low end part that I doubt getting documentation for will be very hard. And according to Documentation/power/video.txt this is one of the cases that actually works.
What is happening in those POST routines of a video card is typically the code to initialize the memory controller on the video card. Plus a little bit of code to set the video mode. If I read the documentation correctly in a S3 power state only the RAM is preserved. So it does look like the video post is needed.
Hmm. Looking at the ACPI 3.0 spec it appears there is a _ROM method that can be called to get a copy of the ROM image for an onboard video card. Has any one tried that method?
Eric
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