On Tue, Jul 22, 2014 at 05:27:25PM +0100, Stephen Warren wrote: > On 07/22/2014 04:27 AM, Catalin Marinas wrote: > ... > > ...It's also aimed at > > pushing back on hardware people who think they can mess up, for example, > > a GIC implementation because the rest is just software and you can > > always add #ifdefs. > > I'm very concerned about this statement. > > Yes, it would be nice if all HW was sanely designed, but it's not > always. The time to push back on bad HW design is during IP licensing > agreements or HW design reviews, not upstreaming. I agree about the HW design reviews. But I suspect some software people in such companies, concerned with upstreaming Linux support, are allowed to give feedback. And the feedback could be something like (just an example) "if we use a standard GIC and the architected timer, sane (!PL310-like) system caches, we get the benefit of no additional upstream work, better virtualisation support etc". I hope someone in the HW team would take such feedback into account rather than assume that software and upstreaming comes for free. Of course, we've never rejected Linux upstreaming because of the hardware design (well, as long as Linux could reliably run on it) and I don't plan to do this in the future, but just show that there are clear benefits in doing something in a more standardised way (e.g. SBSA for servers). Even though ARM licenses the architecture, there is no way to enforce a HW design as part of the agreement (or risk not licensing the IP at all). But there is effort to standardise things like SBSA, Trusted Firmware. > Any pushback during SW upstreaming simply serves to make it difficult > for the SW people doing the upstreaming. It has zero impact on the > current HW design (it's already shipped). It probably has zero impact on > the next N revisions of the HW (they're already baked). It's possible it > has zero-to-minimal impact on any future HW (end-user product > requirements are what matter most). I agree that pushing back during SW upstreaming is very late. But I hope to raise the awareness earlier for ARMv8 hardware. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
