On Fri, Sep 12, 2025 at 12:31 PM Arnd Bergmann [off-list ref] wrote:

On Wed, Sep 10, 2025, at 22:33, Richard Weinberger wrote:

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Von: "Dave Hansen" [off-list ref]

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Even with a new memory split, which could utilize most of the
available memory, I expect there to be issues with various
applications and FPGA device drivers.

I also remember driver problems on older Marvell NAS systems, which
we never fully figured out, my best guess in retrospect is that these
had devices with DMA address restrictions, and if lowmem is small
enough it would always work, but any lowmem allocation above the
hardware DMA address limit would cause data corruption.

This kind of mess is often also driver problems, in the Kirkwood MMC
driver there is some dated code traversing sglists iteratively
instead of using sg_miter() on !DMA which I think is not entirely
safe either.

I wanted to fix that driver but the hardware is in my NAS and
all the time someone is watching a movie from it :D

Yours,
Linus Walleij