Re: [PATCH] mmc: core: Remove timeout when enabling cache

[Wolfram Sang]

> >> That also happens to be one of the cards we deploy; However i did
> >> wonder about adding a quirk but decided against it as it was not clear
> >> to me from the specification that CACHE ON really is meant to complete
> >> within GENERIC_CMD6_TIMEOUT. That and i fret about ending up in hit-a-
> >> mole games as the failure is really quite tedious (boot failure).
> >
> > I agree that we should use the more defensive variant as a default. I
> > mean there should be no performance regression since most cards will
> > respond just faster, or? The only downside I could see is that we might
> > miss a real timeout with no bounds set and might get stuck?
> 
> Well, you have a point, but still it's kind of nice to know which
> cards are behaving well and which ones that doesn't. Hence I think I
> prefer to stick using a quirk, unless you have a strong opinion.

No strong opinion. Especially not if you say it is in the spec (although
"must be sufficient" would be better than "should be" ;)). Also, I
assume this failure is reproducible and should turn up during
development? Compared to "happens once in a while randomly"?

Yet, if we add a quirk for that, then we should probably mention it in
an error message when we hit -ETIMEDOUT for cache on ("does your card
need this quirk?")? It can be pretty time consuming to track this down
otherwise, I'd think.

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