Re: Radeon S3/resume: VGA ROM POST from kernel

[ole.rohne-vJEk5272eHo@public.gmane.org]

Pavel> Agreed, I like this patch.

Cool... Let's see if it's still like that when I've explained how it
works.

Pavel> If you are adding comment with function name, you should at least
Pavel> explain what the function does... or not add the comment at all.

Sure. Ditto for acpi_restore_state from the stock kernel sources that
I started with:-)

Pavel> Please indent using one tab.

Sorry, I must have forgotten to M-x load linux-c-mode

>> (...)
>> +  do_vgapost_lowlevel(acpi_wakeup_address);
>> (...)

Pavel> This needs BUG_ON(num_online_cpus() != 1) to avoid bad
Pavel> disaster, right?

Sounds like a good idea.

>> testl	$1, video_flags - wakeup_code
>> jz	1f
>> +	movw	video_flags - wakeup_code + 2, %ax
>> lcall   $0xc000,$3

Pavel> Are you sure you wanted to touch this code? Zeroing %ax on entry to
Pavel> BIOS might be good idea, but...

It is absolutely necessary, see below for how I've reused the
real->pmode switch. The VGA BIOS expect the PCI bus/slot/function from
%ax and C passes us that information in the upper 16 bits of
acpi_video_flags.

Pavel> Ouch, so you call wakeup_start once again?

Yes, I didn't want to implement yet another real->pmode switch, it
would have been a blue-print copy of wakeup_start and
acpi_copy_wakeup_routine anyway.

Pavel> ...that's certainly interesting design. Does that mean that
Pavel> 'phony return code' is never reached?

It is never reached and should be deleted. It is just a remnant of an
early test stage.

Pavel> How do you manage to return from this routine?

Precisely like do_suspend_lowlevel_s4bios: calling save_registers and
effectively reusing the tail-end of do_suspend_lowlevel.

Ole


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