On Mon, Oct 3, 2022 at 6:14 AM Jim Shu <jim....@sifive.com> wrote: > > PLIC spec [1] requires interrupt source priority registers are WARL > field and the number of supported priority is power-of-2 to simplify SW > discovery. > > Existing QEMU RISC-V machine (e.g. shakti_c) don't strictly follow PLIC > spec, whose number of supported priority is not power-of-2. Just change > each bit of interrupt priority register to WARL field when the number of > supported priority is power-of-2. > > [1] > https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc#interrupt-priorities > > Signed-off-by: Jim Shu <jim....@sifive.com> > --- > hw/intc/sifive_plic.c | 21 +++++++++++++++++++-- > 1 file changed, 19 insertions(+), 2 deletions(-) > > diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c > index f864efa761..c2dfacf028 100644 > --- a/hw/intc/sifive_plic.c > +++ b/hw/intc/sifive_plic.c > @@ -180,7 +180,15 @@ static void sifive_plic_write(void *opaque, hwaddr addr, > uint64_t value, > if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) { > uint32_t irq = ((addr - plic->priority_base) >> 2) + 1; > > - if (value <= plic->num_priorities) { > + if (((plic->num_priorities + 1) & plic->num_priorities) == 0) { > + /* > + * if "num_priorities + 1" is power-of-2, make each register bit > of > + * interrupt priority WARL (Write-Any-Read-Legal). Just filter > + * out the access to unsupported priority bits. > + */ > + plic->source_priority[irq] = value % (plic->num_priorities + 1); > + sifive_plic_update(plic); > + } else if (value <= plic->num_priorities) { > plic->source_priority[irq] = value; > sifive_plic_update(plic); > } > @@ -207,7 +215,16 @@ static void sifive_plic_write(void *opaque, hwaddr addr, > uint64_t value, > uint32_t contextid = (addr & (plic->context_stride - 1)); > > if (contextid == 0) { > - if (value <= plic->num_priorities) { > + if (((plic->num_priorities + 1) & plic->num_priorities) == 0) { > + /* > + * if "num_priorities + 1" is power-of-2, each register bit > of > + * interrupt priority is WARL (Write-Any-Read-Legal). Just > + * filter out the access to unsupported priority bits. > + */ > + plic->target_priority[addrid] = value % > + (plic->num_priorities + 1); > + sifive_plic_update(plic); > + } else if (value <= plic->num_priorities) { > plic->target_priority[addrid] = value; > sifive_plic_update(plic); > } > -- > 2.17.1
Reviewed-by: Clément Chigot <chi...@adacore.com>
