On 2023/1/20 2:30, 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.
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.
Refer to the corresponding manual,the ISA definition of S7 is: rv64imac_zicsr_zba_zbb, and the ISA definition of U7 is: rv64imafdc_zicsr_zba_zbb, which is consistent with linux.
Thanks! Conor.