Re: [PATCH libdrm] libdrm_amdgpu: add kernel semaphore support

From: "Christian König" <deathsimple@vodafone.de>
To: Dave Airlie <airlied@gmail.com>
Cc: "Olsak, Marek" <Marek.Olsak@amd.com>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	amd-gfx mailing list <amd-gfx@lists.freedesktop.org>
Subject: Re: [PATCH libdrm] libdrm_amdgpu: add kernel semaphore support
Date: Tue, 11 Jul 2017 10:36:17 +0200	[thread overview]
Message-ID: <e8320749-8afb-5d64-93e4-7c64192735c5@vodafone.de> (raw)
In-Reply-To: <CAPM=9twcN5y4H3yvKfUNEK+k4E3_6zoTPpWWsn+vdE2bYt7qhg@mail.gmail.com>

Am 11.07.2017 um 08:49 schrieb Dave Airlie:
> On 7 July 2017 at 19:07, Christian König <deathsimple@vodafone.de> wrote:
>> Hi Dave,
>>
>> on first glance that looks rather good to me, but there is one things I
>> don't really like and I strongly think Marek will absolutely agree on that:
>> When we add a new CS function then let's get ride of all this abstraction!
>>
>> The new function should get an amdgpu_device_handle and a list of chunks to
>> submit, nothing else.
>>
>> When then provide helper functions to generate the chunks out of the
>> existing amdgpu_context_handle and amdgpu_bo_list_handle.
>>
>> That should be perfectly sufficient and extensible for future additions as
>> well.
> Sounds tempting, but it a bit messier than it looks once I started
> digging into it.
>
> The main things I ran up against is the context sequence mutex protecting the
> kernel submissions per context which would be tricky to figure out why that is
> required (should we be submitting from different contexts on different threads?)

The sequence lock is just to keep last_seq up to date and last_seq just 
exists because of amdgpu_cs_signal_semaphore.

We want to get ride of that, so you can drop support for this altogether 
in the new IOCTL.

> I'd prefer to land this then refactor a new interface, I do wonder if
> maybe Marek
> would prefer just doing this all in Mesa and avoiding these APIs a bit more :-)
>
> Once I get the syncobjs in I might look at internally refactoring the
> code a bit more,
> then a new API.

Actually I wanted to propose just to remove the old semaphore API, it 
was never used by Mesa or any other open source user.

So we could get rid of it without breaking anybody. Marek what do you think?

Regards,
Christian.

>
> Dave.
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