Messages in this thread | | | Date | Wed, 19 Apr 2023 08:59:03 -0700 (PDT) | Subject | Re: [PATCH v8 0/7] Add non-coherent DMA support for AX45MP | From | Palmer Dabbelt <> |
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On Sun, 16 Apr 2023 23:53:17 PDT (-0700), Christoph Hellwig wrote: > On Wed, Apr 12, 2023 at 09:32:30PM +0100, Conor Dooley wrote: >> On Wed, Apr 12, 2023 at 12:08:53PM +0100, Prabhakar wrote: >> >> > Note, >> > - This series requires testing on Cores with zicbom and T-Head SoCs >> >> As I said last time, I dunno what actual Zicbom stuff exists, other than >> perhaps the Ventana lads having something. I did some tyre kicking on my >> D1 and it was fine, although nothing has actually changed materially for >> either of them with this series in v8.. > > And as saying before, there is absolutely no reason to add non-standard > non-coherent DMA support and let this cancer creep. If you want Linux > support implement Zicbom, be that in hardware or the SBI.
IMO we should just take the support in Linux: trying to hide stuff behind the SBI leads to more more headaches than it's worth, we end up with a bunch of broken firmware to try and work around. We've already got a mess here because of the D1 support, we might as well just live with it.
In practice there's just going to be a ton of mess in arch/riscv, as the ISA has been missing many core features for many years and hardware vendors are allowed to do whatever they want. That's obviously a huge headache, but I think there's nothing we can really do about it.
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