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Re: [PATCH v2] riscv: plic: Honour source priorities
From: |
Alistair Francis |
Subject: |
Re: [PATCH v2] riscv: plic: Honour source priorities |
Date: |
Fri, 19 Jun 2020 14:13:54 -0700 |
On Thu, Jun 18, 2020 at 1:24 PM Jessica Clarke <jrtc27@jrtc27.com> wrote:
>
> The source priorities can be used to order sources with respect to other
> sources, not just as a way to enable/disable them based off a threshold.
> We must therefore always claim the highest-priority source, rather than
> the first source we find.
>
> Signed-off-by: Jessica Clarke <jrtc27@jrtc27.com>
Thanks for the patch!
This looks good to me, I'll apply it to the RISC-V tree and it'll be
in my next round pull request.
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Alistair
> ---
> Changes since v1:
>
> * Initialise max_prio to plic->target_priority[addrid] rather than 0,
> allowing the target priority comparison to be dropped and covered by
> the max_prio comparison.
>
> hw/riscv/sifive_plic.c | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/hw/riscv/sifive_plic.c b/hw/riscv/sifive_plic.c
> index 4f216c5585..d91e82b8ab 100644
> --- a/hw/riscv/sifive_plic.c
> +++ b/hw/riscv/sifive_plic.c
> @@ -166,6 +166,9 @@ static void sifive_plic_update(SiFivePLICState *plic)
> static uint32_t sifive_plic_claim(SiFivePLICState *plic, uint32_t addrid)
> {
> int i, j;
> + uint32_t max_irq = 0;
> + uint32_t max_prio = plic->target_priority[addrid];
> +
> for (i = 0; i < plic->bitfield_words; i++) {
> uint32_t pending_enabled_not_claimed =
> (plic->pending[i] & ~plic->claimed[i]) &
> @@ -177,14 +180,18 @@ static uint32_t sifive_plic_claim(SiFivePLICState
> *plic, uint32_t addrid)
> int irq = (i << 5) + j;
> uint32_t prio = plic->source_priority[irq];
> int enabled = pending_enabled_not_claimed & (1 << j);
> - if (enabled && prio > plic->target_priority[addrid]) {
> - sifive_plic_set_pending(plic, irq, false);
> - sifive_plic_set_claimed(plic, irq, true);
> - return irq;
> + if (enabled && prio > max_prio) {
> + max_irq = irq;
> + max_prio = prio;
> }
> }
> }
> - return 0;
> +
> + if (max_irq) {
> + sifive_plic_set_pending(plic, max_irq, false);
> + sifive_plic_set_claimed(plic, max_irq, true);
> + }
> + return max_irq;
> }
>
> static uint64_t sifive_plic_read(void *opaque, hwaddr addr, unsigned size)
> --
> 2.20.1
>
>