-----Original Message-----
From: Maarten Lankhorst [mailto:maarten.lankhorst@canonical.com]
Sent: Tuesday, May 28, 2013 12:23 AM
To: Inki Dae
Cc: 'Daniel Vetter'; 'Rob Clark'; 'linux-fbdev'; 'YoungJun Cho'; 'Kyungmin
Park'; 'myungjoo.ham'; 'DRI mailing list'; linux-arm-
kernel@lists.infradead.org; linux-media@vger.kernel.org
Subject: Re: Introduce a new helper framework for buffer synchronization

Hey,

Op 27-05-13 12:38, Inki Dae schreef:

quoted

Hi all,

I have been removed previous branch and added new one with more cleanup.
This time, the fence helper doesn't include user side interfaces and

cache

quoted

operation relevant codes anymore because not only we are not sure that
coupling those two things, synchronizing caches and buffer access

between

quoted

CPU and CPU, CPU and DMA, and DMA and DMA with fences, in kernel side is

a

quoted

good idea yet but also existing codes for user side have problems with

badly

quoted

behaved or crashing userspace. So this could be more discussed later.

The below is a new branch,

https://git.kernel.org/cgit/linux/kernel/git/daeinki/drm-

exynos.git/?h=dma-f

quoted

ence-helper

And fence helper codes,

https://git.kernel.org/cgit/linux/kernel/git/daeinki/drm-

exynos.git/commit/?

quoted

h=dma-fence-helper&id­cbc0fe7e285ce866e5816e5e21443dcce01005

And example codes for device driver,

https://git.kernel.org/cgit/linux/kernel/git/daeinki/drm-

exynos.git/commit/?

quoted

h=dma-fence-helper&idÒce7af23835789602a99d0ccef1f53cdd5caaae

I think the time is not yet ripe for RFC posting: maybe existing dma

fence

quoted

and reservation need more review and addition work. So I'd glad for

somebody

quoted

giving other opinions and advices in advance before RFC posting.

NAK.

For examples for how to handle locking properly, see Documentation/ww-
mutex-design.txt in my recent tree.
I could list what I believe is wrong with your implementation, but real
problem is that the approach you're taking is wrong.

I just removed ticket stubs to show my approach you guys as simple as
possible, and I just wanted to show that we could use buffer synchronization
mechanism without ticket stubs.

Question, WW-Mutexes could be used for all devices? I guess this has
dependence on x86 gpu: gpu has VRAM and it means different memory domain.
And could you tell my why shared fence should have only eight objects? I
think we could need more than eight objects for read access. Anyway I think
I don't surely understand yet so there might be my missing point.

Thanks,
Inki Dae

~Maarten