linux-kernel - Re: [PATCH v6 0/7] spi: spi-fsl-dspi: Target mode improvements

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Message-ID: <20250903131807.cou3u7wa3e266yn7@skbuf>
Date: Wed, 3 Sep 2025 16:18:07 +0300
From: Vladimir Oltean <vladimir.oltean@....com>
To: James Clark <james.clark@...aro.org>
Cc: Vladimir Oltean <olteanv@...il.com>, Mark Brown <broonie@...nel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Larisa Grigore <larisa.grigore@....com>,
	Frank Li <Frank.li@....com>, Christoph Hellwig <hch@....de>,
	linux-spi@...r.kernel.org, imx@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 0/7] spi: spi-fsl-dspi: Target mode improvements

On Tue, Sep 02, 2025 at 01:44:52PM +0100, James Clark wrote:
> Improve usability of target mode by reporting FIFO errors and increasing
> the buffer size when DMA is used. While we're touching DMA stuff also
> switch to non-coherent memory, although this is unrelated to target
> mode.
> 
> With the combination of the commit to increase the DMA buffer size and
> the commit to use non-coherent memory, the host mode performance figures
> are as follows on S32G3:
> 
>   # spidev_test --device /dev/spidev1.0 --bpw 8 --size <test_size> --cpha --iter 10000000 --speed 10000000
> 
>   Coherent (4096 byte transfers): 6534 kbps
>   Non-coherent:                   7347 kbps
> 
>   Coherent (16 byte transfers):    447 kbps
>   Non-coherent:                    448 kbps
> 
> Just for comparison running the same test in XSPI mode:
> 
>   4096 byte transfers:            2143 kbps
>   16 byte transfers:               637 kbps
> 
> These tests required hacking S32G3 to use DMA in host mode, although
> the figures should be representative of target mode too where DMA is
> used. And the other devices that use DMA in host mode should see similar
> improvements.
> 
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
> Changes in v6:
> - Indentation fix
> - Fix trailers in first commit
> - Explain reasoning for "spi: spi-fsl-dspi: Stub out DMA functions"
> - Link to v5: https://lore.kernel.org/r/20250829-james-nxp-spi-dma-v5-0-3246957a6ea9@linaro.org

For the entire set:

Reviewed-by: Vladimir Oltean <vladimir.oltean@....com>