[EXT] Re: v4l2 allocated dma memory

Bing Song bing.song at nxp.com
Fri Apr 2 01:41:31 UTC 2021

But dmabuf map/unmap will handle cache flush/invalidate. So v4l2 without an IOMMU can use cacheable buffer in gstreamer. Right?


-----Original Message-----
From: gstreamer-devel <gstreamer-devel-bounces at lists.freedesktop.org> On Behalf Of Nicolas Dufresne
Sent: 2021年4月2日 2:16
To: Discussion of the development of and with GStreamer <gstreamer-devel at lists.freedesktop.org>
Subject: [EXT] Re: v4l2 allocated dma memory

Caution: EXT Email

Le jeudi 01 avril 2021 à 08:17 +0000, Bing Song a écrit :
> Hi,
> Is v4l2 video decoder output dma memory cacheable or non-cacheable? I 
> found videoconvert performance is bad with v4l2 video dma buffer 
> output buffer. Is it possible to use cacheable v4l2 dma memory?

It's driver decision and the kernel does not provide this information. In general, drivers without an IOMMU (like most of NXP drivers) will use non-cache- able memory allocation which is near unusable by videoconvert (often slower software decode). Most SoC have some converter capability, which can be exposed through an m2m driver and uses with v4l2convert element.

> Regards,
> Bing
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