Messages in this thread Patch in this message | | | From | Guo Ren <> | Date | Tue, 12 Oct 2021 09:22:40 +0800 | Subject | Re: [PATCH 1/2] irqchip/sifive-plic: Fix duplicate mask/unmask for claim/complete |
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On Mon, Oct 11, 2021 at 11:02 PM Anup Patel <anup@brainfault.org> wrote: > > On Mon, Oct 11, 2021 at 6:54 PM <guoren@kernel.org> wrote: > > > > From: Guo Ren <guoren@linux.alibaba.com> > > > > PLIC only has enable-registers not mask/unmask registers. Mixing > > mask/unmask with irq_eoi is wrong, because readl(claim) could mask > > This is an incorrect assumption about readl(claim). When SW does > read(claim) the HW updates internal state that IRQ has been claimed. > The HW can still get same (already claimed) IRQ again before > writel(claim) which will be delivered after writel(claim). Our hw would mask IRQ with readl(claim), so it's unnecessary for our board. I agree some hardware won't mask IRQ after readl(claim), so I put DT-bool to control it.
> > > irq by hardware. We only need mask/unmask to fixup the hardware > > which couldn't claim + mask correctly. > > The handle_fasteoi_irq() only calls unmask_irq() mostly when the > underlying IRQ is threaded. Is there any other case ? When in handle_fasteoi_irq ONESHOT path, it will call: if (desc->istate & IRQS_ONESHOT) mask_irq(desc);
mask_irq->plic_irq_mask->"write 0 to PRIORITY & ENABLE_BASE-bit"
In this IRQ context, it wouldn't call unmask_irq with cond_unmask_eoi_irq when in IRQCHIP_EOI_THREADED. Then the path would writel(hwirq, claim) with irq disabled. static void cond_unmask_eoi_irq(struct irq_desc *desc, struct irq_chip *chip) { ... } else if (!(chip->flags & IRQCHIP_EOI_THREADED)) { chip->irq_eoi(&desc->irq_data); }
When IRQ is disabled in c9xx, writel(hwirq, claim) would be invalid and cause a blocking irq bug.
> > Another fact is that all irqchip drivers using handle_fasteoi_irq() > implement irq_mask/unmask(). C9xx needn't call mask&unmask after readl(claim), because: 1. If hw supports readl(claim) with acquiring irq then the mask/unmask is unnecessary and causes performance problems. 2. When in IRQS_ONESHOT & IRQCHIP_EOI_THREADED path, unnecessary mask operation would cause a blocking irq bug.
> > Regards, > Anup > > > > > If hardware supports claim + mask, it would cause unnecessary > > mask/umak operations. > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > Cc: Thomas Gleixner <tglx@linutronix.de> > > Cc: Marc Zyngier <maz@kernel.org> > > Cc: Palmer Dabbelt <palmer@dabbelt.com> > > Cc: Anup Patel <anup@brainfault.org> > > Cc: Atish Patra <atish.patra@wdc.com> > > --- > > drivers/irqchip/irq-sifive-plic.c | 16 ++++++++++++---- > > 1 file changed, 12 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c > > index cf74cfa82045..0fa46912f452 100644 > > --- a/drivers/irqchip/irq-sifive-plic.c > > +++ b/drivers/irqchip/irq-sifive-plic.c > > @@ -64,6 +64,7 @@ struct plic_priv { > > struct cpumask lmask; > > struct irq_domain *irqdomain; > > void __iomem *regs; > > + bool claim_mask_support; > > }; > > > > struct plic_handler { > > @@ -111,7 +112,7 @@ static inline void plic_irq_toggle(const struct cpumask *mask, > > } > > } > > > > -static void plic_irq_unmask(struct irq_data *d) > > +static void plic_irq_enable(struct irq_data *d) > > { > > struct cpumask amask; > > unsigned int cpu; > > @@ -125,7 +126,7 @@ static void plic_irq_unmask(struct irq_data *d) > > plic_irq_toggle(cpumask_of(cpu), d, 1); > > } > > > > -static void plic_irq_mask(struct irq_data *d) > > +static void plic_irq_disable(struct irq_data *d) > > { > > struct plic_priv *priv = irq_data_get_irq_chip_data(d); > > > > @@ -168,8 +169,8 @@ static void plic_irq_eoi(struct irq_data *d) > > > > static struct irq_chip plic_chip = { > > .name = "SiFive PLIC", > > - .irq_mask = plic_irq_mask, > > - .irq_unmask = plic_irq_unmask, > > + .irq_enable = plic_irq_enable, > > + .irq_disable = plic_irq_disable, > > .irq_eoi = plic_irq_eoi, > > #ifdef CONFIG_SMP > > .irq_set_affinity = plic_set_affinity, > > @@ -181,6 +182,11 @@ static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq, > > { > > struct plic_priv *priv = d->host_data; > > > > + if (!priv->claim_mask_support) { > > + plic_chip.irq_mask = plic_irq_disable; > > + plic_chip.irq_unmask = plic_irq_enable; > > + } > > + > > irq_domain_set_info(d, irq, hwirq, &plic_chip, d->host_data, > > handle_fasteoi_irq, NULL, NULL); > > irq_set_noprobe(irq); > > @@ -298,6 +304,8 @@ static int __init plic_init(struct device_node *node, > > if (WARN_ON(!nr_contexts)) > > goto out_iounmap; > > > > + priv->claim_mask_support = of_property_read_bool(node, "claim-mask-support"); > > + > > error = -ENOMEM; > > priv->irqdomain = irq_domain_add_linear(node, nr_irqs + 1, > > &plic_irqdomain_ops, priv); > > -- > > 2.25.1 > >
-- Best Regards Guo Ren
ML: https://lore.kernel.org/linux-csky/
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