Hey Seán, David, On Thu, Jan 19, 2023 at 01:26:52AM -0500, Sean Anderson wrote: > On 1/19/23 01:18, David Abdurachmanov wrote: > > On Wed, Jan 18, 2023 at 10:19 AM Yanhong Wang > > <yanhong.w...@starfivetech.com> wrote:
> > > + U74_4: cpu@4 { > > > + compatible = "sifive,u74-mc", "riscv"; > > > + reg = <4>; > > > + d-cache-block-size = <64>; > > > + d-cache-sets = <64>; > > > + d-cache-size = <32768>; > > > + d-tlb-sets = <1>; > > > + d-tlb-size = <40>; > > > + device_type = "cpu"; > > > + i-cache-block-size = <64>; > > > + i-cache-sets = <64>; > > > + i-cache-size = <32768>; > > > + i-tlb-sets = <1>; > > > + i-tlb-size = <40>; > > > + mmu-type = "riscv,sv39"; > > > + next-level-cache = <&ccache>; > > > + riscv,isa = "rv64imafdcbsu"; > > > > Looking at SiFive U74 manuals, shouldn't this be RV64GC_Zba_Zbb_Sscofpmf? > > U74 only supports Zba and Zbb bit manip extensions. > > This is from the 21G3.02.00 release manual. > > > > Looking more, S76 core is listed in the manual as supporting up to: > > RV64IMAC_Zicsr_Zifencei_Zba_Zbb_Sscofpmf. > > > > I almost forgot about _Zicsr_Zifencei (which are part of G). Shouldn't > > those be listed too in riscv,isa? AFAIU, Linux just assumes them since they weren't their own thing prior to ISA spec 20191213. I think in- & ex- cluding them are both valid... Yeah. > AFAIK we don't support Z/X in U-Boot. Does the U-Boot ISA string parsing not just ignore un-implemented extensions? If it does ignore things you don't implement, then I think including the Z extensions should be no harm. IMO, it'd be nice to have this string match whatever the hardware can support so that same Devicetree can be used for U-Boot & whatever OS it is booting. That said, I'm yet to be sure that this SoC supports Zba or Zbb. I asked on the corresponding patchset for Linux and the answer I got, not from the vendor, was that it did. To what extent it might (or if it actually does) I have not yet determined. It's not mentioned in any of the documentation that I have got my hands on. I have one of these boards, so am in the process of getting something functional enough on it to actually test that. Thanks! Conor.
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