v4l2 allocated dma memory

Nicolas Dufresne nicolas at ndufresne.ca
Thu Apr 1 18:15:59 UTC 2021

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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