On 8/14/20 8:38 PM, Anup Patel wrote:
On Fri, Aug 14, 2020 at 11:35 PM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
On 14.08.20 19:52, Anup Patel wrote:
On Fri, Aug 14, 2020 at 11:15 PM Heinrich Schuchardt xypron.glpk@gmx.de wrote:
On the Kendryte K210 OpenBSI cannot emulate the rdtime instruction. So we have to use the Sifive CLINT driver to provide riscv_get_time() in SMODE.
Can you elaborate why ?
The rdtime instruction should generate an illegal instruction fault which OpenSBI will emulate.
The RISC-V Instruction Set Manual Volume II Privileged architectur 1.11 has incompatible changes relative to version 1.9.1
mtval on the Kendryte K210 delivers the bad virtual address and not the instruction:
Ahh, I see. The MTVAL CSR is actually legacy MBADADDR CSR and this CSR.
The S-mode software always has working rdtime instruction for all RISC-V systems. If HW does not implement TIME CSR then OpenSBI emulates it. Please don't break this convention for U-Boot S-mode because we do have RISC-V systems where TIME CSR is implemeted in HW so this will patch will break U-Boot S-mode system because on those system we are supposed to use TIME CSR from S-mode.
This patch does not change anything for existing systems. It only allows me to customize U-Boot for the K210 differently. I understand that fixing OpenSBI is a better approach.
lib/sbi/sbi_illegal_insn.c(123) sbi_illegal_insn_handler: insn 0x4114121602, epc 0x8058c168.
The illegal instruction being c01027f3 rdtime a5
In the long run it may make sense to provide backwards compatibility in OpenSBI.
Yes, let's try to explore possible fixes in OpenSBI.
Instead of this patch, try the following change in OpenSBI ...
diff --git a/lib/sbi/sbi_illegal_insn.c b/lib/sbi/sbi_illegal_insn.c index 0e5523f..c8f2e4a 100644 --- a/lib/sbi/sbi_illegal_insn.c +++ b/lib/sbi/sbi_illegal_insn.c @@ -119,12 +119,10 @@ int sbi_illegal_insn_handler(ulong insn, struct sbi_trap_regs *regs) struct sbi_trap_info uptrap;
if (unlikely((insn & 3) != 3)) {
Why do put sbi_get_insn() behind this if and not before it?
if (insn == 0) {insn = sbi_get_insn(regs->mepc, &uptrap);if (uptrap.cause) {uptrap.epc = regs->mepc;return sbi_trap_redirect(regs, &uptrap);}
insn = sbi_get_insn(regs->mepc, &uptrap);if (uptrap.cause) {uptrap.epc = regs->mepc;return sbi_trap_redirect(regs, &uptrap); } if ((insn & 3) != 3) return truly_illegal_insn(insn, regs);
For this illegal instruction exception the fix works. But I think the change is in the wrong place.
We have to cover all exceptions, e.g. unaligned access. So we better should determine the instruction in sbi_trap_handler().
Best regards
Heinrich
Regards, Anup
Without this patch I observe a crash in the loady command. So I cannot load a file over the UART.
Best regards
Heinrich
Regards, Anup