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From: H. Peter Anvin on 9 Apr 2010 16:20
On 04/09/2010 11:55 AM, Guenter Roeck wrote:
> On Fri, 2010-04-09 at 14:23 -0400, H. Peter Anvin wrote:
>> [Adding Guenter Roeck as he was commenting on something writing to the
>> VGA area...]
>>
>> On 04/09/2010 10:22 AM, Yinghai wrote:
>>>
>>> then please check this one
>>>
>>> update e820 at first, and later put them resource tree, but give pci BAR chance to claim
>>> the range, before assign unassigned resources.
>>>
>>> in case some system doesn't have VGA, and use [0xa0000, ..] for mmio of some other pci devices.
>>>
>>
>> Do we have any evidence of any such system?
>>
>> Either which way, the patch looks saner...
>>
> Yes, we have a system which does not have VGA and uses the VGA memory
> space for another device. I don't know exactly what for, but I can find
> out if it is relevant.
>

Quite. We really need to consider if that kind of devices should be
supported.

-hpa
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From: Guenter Roeck on 9 Apr 2010 16:40
On Fri, 2010-04-09 at 16:11 -0400, H. Peter Anvin wrote:
> On 04/09/2010 11:55 AM, Guenter Roeck wrote:
> > On Fri, 2010-04-09 at 14:23 -0400, H. Peter Anvin wrote:
> >> [Adding Guenter Roeck as he was commenting on something writing to the
> >> VGA area...]
> >>
> >> On 04/09/2010 10:22 AM, Yinghai wrote:
> >>>
> >>> then please check this one
> >>>
> >>> update e820 at first, and later put them resource tree, but give pci BAR chance to claim
> >>> the range, before assign unassigned resources.
> >>>
> >>> in case some system doesn't have VGA, and use [0xa0000, ..] for mmio of some other pci devices.
> >>>
> >>
> >> Do we have any evidence of any such system?
> >>
> >> Either which way, the patch looks saner...
> >>
> > Yes, we have a system which does not have VGA and uses the VGA memory
> > space for another device. I don't know exactly what for, but I can find
> > out if it is relevant.
> >
>
> Quite. We really need to consider if that kind of devices should be
> supported.

It is used for a custom FPGA implementing a watchdog timer and some
other functionality.

This is not a matter of supporting such a device in Linux, it is a
matter of explicitly excluding non-VGA devices from using VGA memory
space.

If that is the decision, it might be worthwhile mentioning it somewhere
in the documentation, to prevent others from ever using that memory
space in an embedded system (and to save them the time needed to find
out about it and to identify and implement a workaround).

Guenter


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From: H. Peter Anvin on 9 Apr 2010 16:50
On 04/09/2010 01:31 PM, Guenter Roeck wrote:
>
> It is used for a custom FPGA implementing a watchdog timer and some
> other functionality.
>
> This is not a matter of supporting such a device in Linux, it is a
> matter of explicitly excluding non-VGA devices from using VGA memory
> space.
>
> If that is the decision, it might be worthwhile mentioning it somewhere
> in the documentation, to prevent others from ever using that memory
> space in an embedded system (and to save them the time needed to find
> out about it and to identify and implement a workaround).
>

"Don't use legacy fixed-function addresses for nonstandard purposes."

There, there is your documentation.

-hpa
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From: Guenter Roeck on 9 Apr 2010 17:10
On Fri, 2010-04-09 at 16:44 -0400, H. Peter Anvin wrote:
> On 04/09/2010 01:31 PM, Guenter Roeck wrote:
> >
> > It is used for a custom FPGA implementing a watchdog timer and some
> > other functionality.
> >
> > This is not a matter of supporting such a device in Linux, it is a
> > matter of explicitly excluding non-VGA devices from using VGA memory
> > space.
> >
> > If that is the decision, it might be worthwhile mentioning it somewhere
> > in the documentation, to prevent others from ever using that memory
> > space in an embedded system (and to save them the time needed to find
> > out about it and to identify and implement a workaround).
> >
>
> "Don't use legacy fixed-function addresses for nonstandard purposes."
>
> There, there is your documentation.

Fair and good enough, as long as it is going to show up somewhere.

Guenter


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From: Yinghai Lu on 9 Apr 2010 18:30
On 04/09/2010 03:21 PM, Andy Isaacson wrote:
> On Fri, Apr 09, 2010 at 12:55:39PM -0700, Yinghai wrote:
>
>> update version for test
>>
>> Subject: [PATCH] x86: reserve [0xa0000, 0x100000] in e820
>>
>> Update e820 at first, and later put them resource tree.
>> But give pci BAR chance to claim the range, before assign unassigned resources.
>>
>> In case some system doesn't have VGA, and use [0xa0000, ..] for mmio of some
>> other pci devices.
>>
> This doesn't help, my AHCI still fails to initialize in the same way.
>
>
bootlog?

what is the address used for AHCI?

YH
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