[PATCH] drm/gma500: remove the process of stolen page in page fault handler.

[Patrik Jakobsson]

On Fri, Sep 2, 2016 at 11:31 AM,  <jiang.biao2 at zte.com.cn> wrote:
>
> JiangBiao162664/user/zte_ltd Wrote 2016/08/31 10:27:34:
>
>> JiangBiao162664/user/zte_ltd
>> 2016/08/31 10:27
>>
>> From
>> Patrik Jakobsson <patrik.r.jakobsson at gmail.com>,
>> Re: [PATCH] drm/gma500: remove the process of stolen page in page
>> fault handler.
>>
>> Patrik Jakobsson <patrik.r.jakobsson at gmail.com> wrote on 2016/08/30
>> 18:21:08:
>>
>> > Patrik Jakobsson <patrik.r.jakobsson at gmail.com>
>> > 2016/08/30 18:21
>> >
>> > From
>> > jiang.biao2 at zte.com.cn,
>> > cc
>> > dri-devel <dri-devel at lists.freedesktop.org>
>> > Re: [PATCH] drm/gma500: remove the process of stolen page in page
>> fault handler.
>> >
>> > On Tue, Aug 30, 2016 at 7:10 AM,  <jiang.biao2 at zte.com.cn> wrote:
>> > >
>> > > Direct gtt range is used in the page fault scene in current driver,
>> > > instead of stolen page. So no need to keep relative process.
>> >
>> > Hi
>> >
>> > Are you saying that we don't use stolen memory? Afaik stolen memory
>> > should be accessed through the stolen range so we do need this.
>> >
>> > -Patrik
>> >
>> As far as I can see, the stolen memory is only used by fbdev driver
>> in gma500,
>> but the fbdev driver maps the stloen memory directly in psbfb_vm_fault,
>> not
>> using psb_gem_fault to map the stolen memory.
>> The only scenario using the psb_gem_fault is the gtt range created by
>> psb_gem_create, which alloc the gtt range without stolen memory backed.
>
>> If I missed something, pls enlighten me.
>> Thanks a lot.
>
> Hi Patrik,
>
> Could you please help to confirm my question?
> Thank you very much.

Hi,

The assumption that stolen memory will never be used with
psb_gem_create() might not hold true in the future and silently
breaking support for it ito save a few lines of code is not the right
way to do it. Actually, if we find use for stolen memory we would
basically get memory for free since it is already reserved for
graphics usage.

Cheers
Patrik