On 1/19/23 13:30, Conor Dooley wrote:
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.wang@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.
We use strchr on it; so something like Zicsr is parsed as 5 extensions.
See supports_extension for details
--Sean
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.