[U-Boot] [linux-sunxi] Re: [PATCH 2/3] net/designware: invalidate entire descriptor in dw_eth_send

[Ian Campbell]

On Sat, 2014-04-19 at 10:14 -0400, Stefan Monnier wrote:
> > Some platforms cannot invalidate the cache at four byte intervals, so
> > invalidate the entire descriptor.
> 
> Wouldn't it be simpler to make invalidate_dcache_range round up to the
> nearest aligned boundaries?
> 
> Can there ever be situations where invalidating "too much" could be
> a problem?

Yes, if there was any data you cared about in the rounded up region
after the region you were actually trying to invalidate.

"invalidate" here means "throw away the content of the cache line
without writing back to ram", which is what you want if the content of
RAM is more up to date than the cache (because the device has DMAd to
it).

So invalidating more than was asked for would more than likely lead to
subtle errors.

Ian.