ongoing writecombine on ppc

[Oded Gabbay]

On Fri, Oct 2, 2015 at 7:56 AM, Benjamin Herrenschmidt
<benh at kernel.crashing.org> wrote:
> On Fri, 2015-10-02 at 14:53 +1000, Dave Airlie wrote:
>> On 2 October 2015 at 14:45, Benjamin Herrenschmidt
>> <benh at kernel.crashing.org> wrote:
>> > On Fri, 2015-10-02 at 14:42 +1000, Dave Airlie wrote:
>> > > I don't think we resolved this the last time we talked about it,
>> > >
>> > > but radeon writecombine maps fail hard on ppc, I think all the
>> > > fixes
>> > > either did something bad to AGP systems or weren't liked.
>> > >
>> > > My patch attached just fixes radeon, which is where I'm still
>> > > seeing
>> > > the issue.
>> >
>> > Yes, you MUST NOT set the flags of system memory to anything other
>> > than
>> > fully cachable on any cache coherent powerpc machine. This should
>> > be
>> > bolted into the DRM core imho.
>> >
>>
>> Except you guys screwed up and allowed AGP to exist on Power, and
>> that requires it.
>
> Well, Apple did :-) Yes, AGP should never have existed in the first
> place, I think that's a given :)
>
>> So we have to keep the AGP trapdoor in place, and at the moment only
>> the drivers know if they are AGP, hence why I had to add this in the
>> driver instead of in the drm core.
> Cheers,
> Ben.
>
>
>
Bumping this and adding my r-b:
Reviewed-by: Oded Gabbay <oded.gabbay at gmail.com>