From: Mikko Perttunen <cyndis@kapsi.fi>
To: Daniel Vetter <daniel@ffwll.ch>, Dmitry Osipenko <digetx@gmail.com>
Cc: Mikko Perttunen <mperttunen@nvidia.com>,
Thierry Reding <thierry.reding@gmail.com>,
Jon Hunter <jonathanh@nvidia.com>, Dave Airlie <airlied@linux.ie>,
linux-tegra <linux-tegra@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
talho@nvidia.com, bhuntsman@nvidia.com
Subject: Re: [PATCH v3 19/20] drm/tegra: Implement new UAPI
Date: Tue, 20 Oct 2020 15:51:01 +0300 [thread overview]
Message-ID: <ec4138c0-6c7f-b32e-2049-7848b6ac7f6b@kapsi.fi> (raw)
In-Reply-To: <CAKMK7uFWyMZQauakjzSWa9r494R4JKDkAk6ABZOLLsCXb6_yHg@mail.gmail.com>
On 10/20/20 2:40 PM, Daniel Vetter wrote:
> On Mon, Oct 19, 2020 at 7:27 PM Dmitry Osipenko <digetx@gmail.com> wrote:
>>
>> 19.10.2020 11:13, Mikko Perttunen пишет:
>>> On 10/19/20 5:21 AM, Dmitry Osipenko wrote:
>>>> 07.10.2020 20:12, Mikko Perttunen пишет:
>>>>> +int tegra_drm_ioctl_channel_map(struct drm_device *drm, void *data,
>>>>> + struct drm_file *file)
>>>>> +{
>>>>
>>>> Hello, Mikko!
>>>>
>>>> Could you please tell what are the host1x clients that are going to be
>>>> upstreamed and will need this IOCTL?
>>>>
>>>
>>> Hi Dmitry!
>>>
>>> It is needed for any engine/job that wants to access memory, as this
>>> IOCTL must be used to map memory for the engine. So all of them.
>>>
>>> Downstream doesn't have an equivalent IOCTL because it (currently) does
>>> mapping at submit time, but that is suboptimal because
>>>
>>> - it requires doing relocations in the kernel which isn't required for
>>> T186+
>>> - it's a big performance penalty, due to which the downstream kernel has
>>> the "deferred dma-buf unmapping" feature, where unmapping a dma_buf may
>>> not immediately unmap it in case it's used later, so that the "mapping"
>>> later is faster. A feature which we'd preferably get rid of.
>>> - because of the above feature not being controlled by the user, it can
>>> cause variance in submit times.
>>>
>>> On the other hand, we cannot (at least always) do the mapping at
>>> allocation/import time, because
>>>
>>> - A single FD may have multiple channel_ctx's, and an allocation/import
>>> may need to be used in any subset of them
>>> - The import IOCTL is fixed and doesn't have the parameters we'd need to
>>> do this at import time
>>> - Overall it's more orthogonal to have GEM object acquirement in one
>>> step and mapping in another.
>>>
>>> Maybe that's not quite what you asked, but it's some background anyway :)
>>
>> I'm asking this question because right now there is only one potential
>> client for this IOCTL, the VIC. If other clients aren't supposed to be a
>> part of the DRM driver, like for example NVDEC which probably should be
>> a V4L driver, then DRM driver will have only a single VIC and in this
>> case we shouldn't need this IOCTL because DRM and V4L should use generic
>> dmabuf API for importing and exporting buffers.
>
> Randomly jumping in here ...
>
> So if you have a drm driver with userspace in mesa3d already, the
> usual approach is to have a libva implementation (ideally in mesa3d
> too, using the gallium framework so that a lot of the boring
> integration glue is taken care of already) directly on top of drm. No
> v4l driver needed at all here.
>
> And it sounds like this nvdec thing would fit that bill pretty neatly.
Something like this would be my preference as well.
Mikko
>
>> I'm also not quite sure about whether the current model of the unified
>> Tegra DRM driver is suitable for having the separated engines. Perhaps
>> each separated engine should just have its own rendering node?
>
> Above model using libva driver in userspace for nvdec would avoid this
> issue too.
> -Daniel
>
next prev parent reply other threads:[~2020-10-20 12:51 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-07 17:12 [PATCH v3 00/20] Host1x/TegraDRM UAPI Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 01/20] gpu: host1x: Use different lock classes for each client Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 02/20] gpu: host1x: Allow syncpoints without associated client Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 03/20] gpu: host1x: Show number of pending waiters in debugfs Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 04/20] gpu: host1x: Remove cancelled waiters immediately Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 05/20] gpu: host1x: Use HW-equivalent syncpoint expiration check Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 06/20] gpu: host1x: Cleanup and refcounting for syncpoints Mikko Perttunen
2020-10-07 22:23 ` kernel test robot
2020-10-07 17:12 ` [PATCH v3 07/20] gpu: host1x: Introduce UAPI header Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 08/20] gpu: host1x: Implement /dev/host1x device node Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 09/20] gpu: host1x: DMA fences and userspace fence creation Mikko Perttunen
2020-10-07 23:13 ` kernel test robot
2020-10-08 11:13 ` kernel test robot
2020-10-07 17:12 ` [PATCH v3 10/20] gpu: host1x: Add no-recovery mode Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 11/20] gpu: host1x: Add job release callback Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 12/20] gpu: host1x: Add support for syncpoint waits in CDMA pushbuffer Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 13/20] gpu: host1x: Reset max value when freeing a syncpoint Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 14/20] gpu: host1x: Reserve VBLANK syncpoints at initialization Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 15/20] drm/tegra: Add new UAPI to header Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 16/20] drm/tegra: Boot VIC during runtime PM resume Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 17/20] drm/tegra: Set resv fields when importing/exporting GEMs Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 18/20] drm/tegra: Allocate per-engine channel in core code Mikko Perttunen
2020-10-07 17:12 ` [PATCH v3 19/20] drm/tegra: Implement new UAPI Mikko Perttunen
2020-10-08 3:42 ` kernel test robot
2020-10-19 2:21 ` Dmitry Osipenko
2020-10-19 8:13 ` Mikko Perttunen
2020-10-19 17:27 ` Dmitry Osipenko
2020-10-20 9:18 ` Mikko Perttunen
2020-10-22 4:20 ` Dmitry Osipenko
2020-10-26 9:11 ` Mikko Perttunen
2020-10-27 19:06 ` Dmitry Osipenko
2020-10-28 9:54 ` Mikko Perttunen
2020-10-30 23:13 ` Dmitry Osipenko
2020-11-09 14:53 ` Mikko Perttunen
2020-11-12 18:35 ` Dmitry Osipenko
2020-10-20 11:40 ` Daniel Vetter
2020-10-20 12:51 ` Mikko Perttunen [this message]
2020-10-07 17:12 ` [PATCH v3 20/20] drm/tegra: Add job firewall Mikko Perttunen
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