linux-kernel - Re: [PATCH 10/10] gpu: host1x: Optionally block when acquiring channel

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Message-ID: <dcb8c4ef-9eb9-556f-cc96-651a50636afa@gmail.com>
Date:   Sat, 11 Nov 2017 00:15:11 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mikko Perttunen <cyndis@...si.fi>,
        Mikko Perttunen <mperttunen@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/10] gpu: host1x: Optionally block when acquiring
 channel

On 07.11.2017 18:29, Dmitry Osipenko wrote:
> On 07.11.2017 16:11, Mikko Perttunen wrote:
>> On 05.11.2017 19:14, Dmitry Osipenko wrote:
>>> On 05.11.2017 14:01, Mikko Perttunen wrote:
>>>> Add an option to host1x_channel_request to interruptibly wait for a
>>>> free channel. This allows IOCTLs that acquire a channel to block
>>>> the userspace.
>>>>
>>>
>>> Wouldn't it be more optimal to request channel and block after job's pining,
>>> when all patching and checks are completed? Note that right now we have locking
>>> around submission in DRM, which I suppose should go away by making locking fine
>>> grained.
>>
>> That would be possible, but I don't think it should matter much since contention
>> here should not be the common case.
>>
>>>
>>> Or maybe it would be more optimal to just iterate over channels, like I
>>> suggested before [0]?
>>
>> Somehow I hadn't noticed this before, but this would break the invariant of
>> having one client/class per channel.
>>
> 
> Yes, currently there is a weak relation of channel and clients device, but seems
> channels device is only used for printing dev_* messages and device could be
> borrowed from the channels job. I don't see any real point of hardwiring channel
> to a specific device or client.

Although, it won't work with syncpoint assignment to channel.