[help]: k230 CLINT device questions

[yf13]

Help

Can you please teach answers for the following CLINT questions:

• The offsets for the MTIME and MTIMECMP registers from the CLINT base address?
• The frquency of the MTIMER in CLINT?
• The meaning of the clint,has-no-64bit-mmio flag in k230.dtsi. Does it mean that we can't access CLINT registers with 64 bit load/store instructions?
• Are there any use of the CLINT in current K230 SDK? if yes, please teach the folder name.

[cyyself]

• The address offsets for the MTIME and MTIMECMP registers?

  You can refer to the k230.dtsi, which is correct.

• The frquency of the MTIMER in CLINT?

  That is timebase-frequency in dts, which is 27000000.

• The meaning of the clint,has-no-64bit-mmio flag in k230.dtsi. Does it mean that we can't access CLINT registers with 64 bit load/store instructions?

  Yes. If you want to use the mainline kernel and OpenSBI, you can replace "riscv,clint0" with "thead,c900-clint" and replace "riscv,plic0" with "thead,c900-plic". Both of them imply "clint,has-no-64bit-mmio" and it has been supported in mainline kernel and opensbi.

  Once you have changed "riscv,plic0" to "thead,c900-plic", you need to specify the IRQ type (i.e. LEVEL or EDGE) in the dts. See my changes here.

[yf13]

@cyyself thanks a lot.

It seems that the hw.dtb used with big core opensbi uses 8Mhz timebase-freqency, maybe that is not used at all?

[yf13]

@wuwentao do you know the actual frequency of the CLINT timer frequencies of the two CPUs? If they are different, please teach.

[yf13]

@cyyself thanks for sharing the information.

With your suggested tweaks of u-boot in #48, I can run NuttX w/ MMU support on K230 using standard Risc-V compliant PTE format. I also did simple test with NuttX that 27Mhz works fine with CPU0.

I also can run mainline OpenSBI with test payload on CanMV-k230, though NuttX payload still not working right yet.

[wangjianxin-canaan]

@cyyself thanks a lot.

It seems that the hw.dtb used with big core opensbi uses 8Mhz timebase-freqency, maybe that is not used at all?

yes ,not used at all,hw.dtb is use only in big core opensbi.

[wangjianxin-canaan]

@wuwentao do you know the actual frequency of the CLINT timer frequencies of the two CPUs? If they are different, please teach. both is 27Mhz