On 2 Dec 2016 19:20, "Tom Rini" <tr...@konsulko.com> wrote: > > On Fri, Dec 02, 2016 at 04:25:37PM +0000, Ryan Harkin wrote: > > On 2 December 2016 at 15:41, Tom Rini <tr...@konsulko.com> wrote: > > > On Fri, Dec 02, 2016 at 11:51:07AM +0000, Ryan Harkin wrote: > > > > > >> I've been working with Soby Mathew to get U-Boot booting on ARM's > > >> AEMv8 FVP model in Aarch32 mode. > > >> > > >> Soby worked out what needed to be changed and I'm refining the changes > > >> into patches that can be built for both Aarch64 and Aarch32 mode. > > >> > > >> There are two patches for discussion: > > >> > > >> [RFC PATCH 1/2] Add Aarch32 option for ARMv8 CPUs > > >> [RFC PATCH 2/2] Add vexpress_aemv8a_aarch32 variant > > >> > > >> I expect the first patch to be controversial. I also don't expect it to > > >> be accepted, but to demonstrate what changes we needed to make to get an > > >> ARMv8 platform to boot in Aarch32 mode when selecting CPU_V7 instead of > > >> ARM64 as the CPU type. This in itself may be the wrong approach. > > >> > > >> It adds an ARMV8_AARCH32 config option and some checks in generic code > > >> for that option to allow the code to differentiate between the two > > >> modes. > > >> > > >> The second patch should be less controversial. It adds support for a > > >> new AEMv8 variant that runs in 32-bit mode. The most awkward part is > > >> that it defines itself not as ARM64, but as CPU_V7. I expect this to > > >> change based on feedback from patch 1/2. > > >> > > >> The Aarch32 code runs on the same AEMv8 model as the Aarch64 code, but > > >> takes an extra per-core model launch parameter to switch the cores into > > >> Aarch32 mode, eg. "-C cluster0.cpu0.CONFIG64=0". > > > > > > So my first and slightly ignorant question is, why isn't this just a new > > > regular ARMv7 board being added rather than a special cased ARMv8? > > > > > > > That's a valid question. > > > > I guess it could be either. At the moment, it's a bit of both. > > arch/arm/Kconfig says it's an ARMv7, but then it's added to > > board/armltd/vexpress64/Kconfig to re-use vexpress_aemv8a.h. > > > > But there's no reason it couldn't be added to > > board/armlt/vexpress/Kconfig and have a copy of vexpress_aemv8a.h that > > isn't special cased at all. That approach seems more copy/paste-y > > than what I've done in this series, though. > > > > I think the whole setup for vexpress/vexpress64 and AEMv8/Juno is > > confused. Really, all of these armlt boards are the same with minor > > variations, even if the minor variation could be ARMv7 vs ARMv8. > > Maybe this gets to the heart of the problem then, and we should > re-structure and fix this. If you look in board/raspberrypi/rpi/ we > support rpi1 2 and 3, and that includes rpi3 in 64bit mode. So if we > want to re-work board/armlt/vexpress/ to support the various ways the > base hardware can be (/ has been over the years), lets. Does that sound > like a plan? >
Thanks, yes, it sounds like a great idea. I haven't looked at the rpi stuff yes, but I'll check it out next week. I believe that would only resolve the issues in my 2nd patch, though. Wouldn't the generic part of using an ARMv8 CPU with the ARMv7 code still need addressing? I guess reviewing the rpi3 code will tell me more. > -- > Tom _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
