Re: [PATCH v2] staging: vc04_services: Replace dmac_map_area with dmac_map_sg

From: Eric Anholt
Date: Wed Oct 26 2016 - 20:57:37 EST


Michael Zoran <mzoran@xxxxxxxxxxxx> writes:

> The original arm implementation uses dmac_map_area which is not
> portable. Replace it with an architecture neutral version
> which uses dma_map_sg.
>
> As you can see that for larger page sizes, the dma_map_sg
> implementation is faster then the original unportable dma_map_area
> implementation.
>
> Test dmac_map_area dma_map_page dma_map_sg
> vchiq_test -b 4 10000 51us/iter 76us/iter 76us
> vchiq_test -b 8 10000 70us/iter 82us/iter 91us
> vchiq_test -b 16 10000 94us/iter 118us/iter 121us
> vchiq_test -b 32 10000 146us/iter 173us/iter 187us
> vchiq_test -b 64 10000 263us/iter 328us/iter 299us
> vchiq_test -b 128 10000 529us/iter 631us/iter 595us
> vchiq_test -b 256 10000 2285us/iter 2275us/iter 2001us
> vchiq_test -b 512 10000 4372us/iter 4616us/iter 4123us

Reviewed-by: Eric Anholt <eric@xxxxxxxxxx>

Nice work! More portability and better performance at the same time.

A possible future improvement would be to track the pagelist, num_pages,
and pagelist_size in a struct in the bulk->remote_data so we didn't need
to recalculate them at free time.

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