linux-kernel - Re: [PATCH v3 4/6] spi: spi-fsl-dspi: Use non-coherent memory for DMA

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Message-Id: <a7c71ee8-0931-4af3-a68f-3f21fea840d3@app.fastmail.com>
Date: Thu, 26 Jun 2025 11:38:46 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "James Clark" <james.clark@...aro.org>, "Frank Li" <Frank.li@....com>
Cc: "Vladimir Oltean" <olteanv@...il.com>, "Mark Brown" <broonie@...nel.org>,
 "Vladimir Oltean" <vladimir.oltean@....com>,
 "Larisa Grigore" <larisa.grigore@....com>, "Christoph Hellwig" <hch@....de>,
 linux-spi@...r.kernel.org, imx@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/6] spi: spi-fsl-dspi: Use non-coherent memory for DMA

On Thu, Jun 26, 2025, at 11:14, James Clark wrote:
> On 25/06/2025 4:04 pm, Frank Li wrote:
>>
>> The cover letter will be lost after patch merge. When someone run git log
>> after some year later, they need know why need this change , what purpose ...
>> 
> I somewhat disagree with this. Usually maintainers add a 'Link:' to the 
> mailing list when applying patches, so the cover letter shouldn't be 
> lost. And these particular performance test results are short lived, in 
> several years time other things may have changed. The performance is 
> related to a specific device and the state of the rest of the kernel at 
> this time. Additionally, I mentioned that it's the combination of two 
> commits. In order to put figures on this commit message I would have to 
> run another set of tests with only this commit and not the one to 
> increase the buffer size which comes after. I did consider reversing the 
> order of them to do this, but it wasn't straightforward, and I really 
> didn't think it was worth the effort when I can just put the figures on 
> the cover letter.

If you submit your changes as a pull request for inclusion, the
common solution is to put the cover letter into the signed tag,
which then gets used as both the description in 'git request-pull'
and in the merge commit.

See e.g. commit 5b31d2d81a4b ("spi: sh-msiof: Transfer size
improvements and I2S") for how a similar series on another driver
shows up in the git log.

    Arnd