[Linaro-acpi] [PATCH v5 18/18] Documentation: ACPI for ARM64
Mark Brown
broonie at kernel.org
Wed Jan 7 12:05:30 PST 2015
On Wed, Jan 07, 2015 at 08:48:48PM +0100, Arnd Bergmann wrote:
> On Wednesday 07 January 2015 12:44:56 Jon Masters wrote:
> > On 01/07/2015 12:27 PM, Mark Brown wrote:
> > > That level of hardware compatibility does partly come from the need to
> > > run existing software. I'd expect that similar effects will start to
> > > come into play with ARMv8 ACPI systems if they become successful; people
> > > will do things like ensure compatibility with common IPs that have
> > > existing Linux drivers that distros tend to include as standard.
> > Agreed.
> There are two problems I see in trying to do the same thing on ARM:
> * we don't have a single vendor that makes de-facto standards that
> everyone else has to copy in the way that the few remaining x86
> vendors copy everything that Intel does. In fact, we prefer to
> have a large number of independent vendors.
Right, I'd guess that (modulo any standards being defined and becoming
successful) it'll more be a case of vendors keeping compatibility with
their own stuff. We *are* seeing greater reliance on off the shelf IPs
for more boring things like DMA and basic bus controllers but there's
plenty of other areas that still affect servers.
> * There is a general mindset about deprecating unwanted features
> early. ARMv8 aarch32 bit mode removes support for older instructions
> or makes them optional. Even the virtualization mode doesn't allow
> to trap on architecture version specific differences, so you can't
> completely emulate an older architecture level.
> This is nice for implementers but not so much for users that rely
> on old (mis-)features. It's also not just the CPU core, other
> components also get easily replaced, like a GICv3 that is not
> a strict superset of GICv2.
This is indeed worrying, though hopefully the fact that we're already
seeing negative impacts in the app ecosystem for Android will have
focused some minds - once you're talking about full system images it
gets even more fun.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 473 bytes
Desc: Digital signature
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20150107/f0e9f2b2/attachment.sig>
More information about the linux-arm-kernel
mailing list