Uwatec Smart Z data download takes 1.5 hours for only 4 dives

Linus Torvalds torvalds at linux-foundation.org
Sun Dec 29 14:32:15 UTC 2013


On Sun, Dec 29, 2013 at 6:39 AM, Sape Sikkema <s.sikkema at telfort.nl> wrote:
>
> Indeed, the dongle is a SigmaTel STIr 4200, its ID is 066f:4200. It did not
> come with the dive computer. It was a $5.00 purchase from a webshop in
> Hongkong.

While I don't have a dongle or target yet, mind trying a few things?

If you can recompile your kernel with CONFIG_HZ set to just 100, that
would be interesting to see. The STIR4200 driver ends up doing busy
loops for some delays *if* those busy loops are shorter than one
kernel tick, and that means that the exact setting of CONFIG_HZ can
matter.

There have been basically no changes to that driver in the last
several years (all of the current git history), but the slowdowns can
obviously come from unrelated infrastructure changes (like, for
example, that timeout handling change due to HZ changes). So..

            Linus


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