[U-Boot] [RFC/PATCH] davinci: disable dcache on boards with EMAC

[Wolfgang Denk]

Dear Tom Rini,

In message <CA+M6bXkFRqkzRtiPuLYN9Zi8ZtXCYQS+LAT4pbKD0nmb3NONdQ at mail.gmail.com> you wrote:
>
> > Why do we have to permanently disable the data cache just because the
> > network driver is broken?  USB is also broken, and probably other
> > drivers as well.
> 
> To be clear, the problem is that today the driver is broken (not cache
> safe) and this series of patches fixes that problem.  In doing so we
> expose that arm926ejs doesn't have complete cache support today.

But the cahce support works fine for a lot of things - basicly
everything except for the broken drivers.  Why do you want to make ALL
user suffer from this, even if they don't intend to use the broken
driver(s) at all?

For example, booting from NAND is probably MUCH faster with caches on.
Why should we make this slower than necessary?

> But cache support is incomplete is the problem.  None of the flushing
> operations exist.

Then fix _THAT_.

> > It should be sufficient to switch the cache off ("dc off") before
> > runnign any network related commands (and you want to make sure to
> > switch it on again afterwards).
> 
> We can't because we can't compile the driver, once we make it cache
> safe.  It's not today and at least anecdotally the driver doesn't work
> today on these platforms unless you turn off dcache.

We cannot _compile_ the driver?  That's even worse and needs to be
fixed.

> As a tangent, is pushing new network drivers that aren't cache safe OK
> if we just say that you need to turn off the dcache before using?

No.  We should not accept any such drivers any more.


Best regards,

Wolfgang Denk

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