Re: [PATCH v4 3/4] i2c: imx: use readb_relaxed and writeb_relaxed

[Arnd Bergmann]

On Wed, Oct 2, 2024, at 11:19, Stefan Eichenberger wrote:
> From: Stefan Eichenberger <stefan.eichenberger@xxxxxxxxxxx>
>
> Use the relaxed version of readb and writeb to reduce overhead. It is
> safe to use the relaxed version because we either do not rely on dma
> completion, or we use a dma callback to ensure that the dma transfer is
> complete before we continue.

I would still consider this a bug in general, you should
never default to the unsafe variants.

If there is a codepath that needs the barrierless version,
please add imx_i2c_write_reg_relaxed()/imx_i2c_read_reg_relaxed()
helpers that use those only in the places where it makes
a measurable difference, with a comment that explains
the usage.

     Arnd