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lib: sbi_illegal_insn: Add emulation for fence.tso

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While OpenC906 appears to properly decode `fence.tso` as a fence
instruction[1], the version of the C906 taped out in the Allwinner D1
does not, and raises illegal instruction.

Handle this errata by emulating `fence.tso` as `fence rw, rw`.

[1]: https://github.com/T-head-Semi/openc906/blob/30827e7f/C906_RTL_FACTORY/gen_rtl/idu/rtl/aq_idu_id_decd.v#L2097

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Samuel Holland
2022-05-29 13:25:30 -05:00
committed by Anup Patel
parent ff65bfec4e
commit cb8271c8e4
2 changed files with 16 additions and 1 deletions
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3
include/sbi/riscv_encoding.h
View File

@@ -838,6 +838,9 @@
#define INSN_MASK_WFI 0xffffff00
#define INSN_MATCH_WFI 0x10500000
#define INSN_MASK_FENCE_TSO 0xffffffff
#define INSN_MATCH_FENCE_TSO 0x8330000f
#define INSN_16BIT_MASK 0x3
#define INSN_32BIT_MASK 0x1c

14
lib/sbi/sbi_illegal_insn.c
View File

@@ -8,6 +8,7 @@
*/
#include <sbi/riscv_asm.h>
#include <sbi/riscv_barrier.h>
#include <sbi/riscv_encoding.h>
#include <sbi/sbi_bitops.h>
#include <sbi/sbi_emulate_csr.h>
@@ -33,6 +34,17 @@ static int truly_illegal_insn(ulong insn, struct sbi_trap_regs *regs)
return sbi_trap_redirect(regs, &trap);
}
static int misc_mem_opcode_insn(ulong insn, struct sbi_trap_regs *regs)
{
/* Errata workaround: emulate `fence.tso` as `fence rw, rw`. */
if ((insn & INSN_MASK_FENCE_TSO) == INSN_MATCH_FENCE_TSO) {
smp_mb();
return 0;
}
return truly_illegal_insn(insn, regs);
}
static int system_opcode_insn(ulong insn, struct sbi_trap_regs *regs)
{
int do_write, rs1_num = (insn >> 15) & 0x1f;
@@ -92,7 +104,7 @@ static const illegal_insn_func illegal_insn_table[32] = {
truly_illegal_insn, /* 0 */
truly_illegal_insn, /* 1 */
truly_illegal_insn, /* 2 */
truly_illegal_insn, /* 3 */
misc_mem_opcode_insn, /* 3 */
truly_illegal_insn, /* 4 */
truly_illegal_insn, /* 5 */
truly_illegal_insn, /* 6 */