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 <25c2fafc-a479-911f-a7df-704108da5dc7@wdc.com>
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From:   Anup Patel <anup@brainfault.org>
Date:   Fri, 30 Nov 2018 09:21:06 +0530
Message-ID: <CAAhSdy2kJD=L=U=uJ0XM5MDtsTJKuH_yU+VZBoFg-jKOXL0yYg@mail.gmail.com>
Subject: Re: [PATCH v2 2/4] irqchip: sifive-plic: More flexible plic_irq_toggle()
To:     Atish Patra <atish.patra@wdc.com>
Cc:     Palmer Dabbelt <palmer@sifive.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Jason Cooper <jason@lakedaemon.net>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Christoph Hellwig <hch@infradead.org>,
        linux-riscv@lists.infradead.org,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Fri, Nov 30, 2018 at 7:09 AM Atish Patra <atish.patra@wdc.com> wrote:
>
> On 11/27/18 2:03 AM, Anup Patel wrote:
> > We make plic_irq_toggle() more generic so that we can enable/disable
> > hwirq for given cpumask. This generic plic_irq_toggle() will be
> > eventually used to implement set_affinity for PLIC driver.
> >
> > Signed-off-by: Anup Patel <anup@brainfault.org>
> > ---
> >   drivers/irqchip/irq-sifive-plic.c | 79 +++++++++++++++----------------
> >   1 file changed, 39 insertions(+), 40 deletions(-)
> >
> > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> > index 56fce648a901..95b4b92ca9b8 100644
> > --- a/drivers/irqchip/irq-sifive-plic.c
> > +++ b/drivers/irqchip/irq-sifive-plic.c
> > @@ -55,19 +55,26 @@
> >   #define     CONTEXT_THRESHOLD               0x00
> >   #define     CONTEXT_CLAIM           0x04
> >
> > -static void __iomem *plic_regs;
> > -
> >   struct plic_handler {
> >       bool                    present;
> > -     int                     ctxid;
> >       void __iomem            *hart_base;
> >       raw_spinlock_t          enable_lock;
> >       void __iomem            *enable_base;
> >   };
> > +
> >   static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
> >
> > -static inline void plic_toggle(struct plic_handler *handler,
> > -                             int hwirq, int enable)
> > +struct plic_hw {
> > +     u32                     nr_irqs;
> > +     u32                     nr_handlers;
> > +     u32                     nr_mapped;
>
> Why these three are moved inside a structure? I don't see them being
> used outside plic_init. Am I missing something ?

Yes, these are not used outside plic_init at the moment but these will be
eventually used to implement pm_suspend() and pm_resume() callbacks.

In general, these details can be used for debug sanity checks as well
since these are critical details about PLIC HW.

>
> > +     void __iomem            *regs;
> > +     struct irq_domain       *irqdomain;
> > +};
> > +
> > +static struct plic_hw plic;
> > +
> > +static void plic_toggle(struct plic_handler *handler, int hwirq, int enable)
> >   {
> >       u32 __iomem *reg = handler->enable_base + (hwirq / 32);
> >       u32 hwirq_mask = 1 << (hwirq % 32);
> > @@ -80,27 +87,23 @@ static inline void plic_toggle(struct plic_handler *handler,
> >       raw_spin_unlock(&handler->enable_lock);
> >   }
> >
> > -static inline void plic_irq_toggle(struct irq_data *d, int enable)
> > +static void plic_irq_toggle(const struct cpumask *mask, int hwirq, int enable)
> >   {
> >       int cpu;
> >
> > -     writel(enable, plic_regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID);
> > -     for_each_cpu(cpu, irq_data_get_affinity_mask(d)) {
> > -             struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
> > -
> > -             if (handler->present)
> > -                     plic_toggle(handler, d->hwirq, enable);
> > -     }
> > +     writel(enable, plic.regs + PRIORITY_BASE + hwirq * PRIORITY_PER_ID);
> > +     for_each_cpu(cpu, mask)
> > +             plic_toggle(per_cpu_ptr(&plic_handlers, cpu), hwirq, enable);
>
> Any specific reason to remove the handler->present check.
>
> Moreover, only this part matches commit text. Most of the other changes
> looks like cosmetic cleanup because of variable is moved to a structure.
> May be separate patch for those changes if they are are required at all.

Actually, these are two changes:
1. Making plic_irq_toggle() flexible
2. Add struct plic_hw to represent global PLIC HW details

I agree this patch is still a mess. I had broken down one big patch into
a patch series at time of sending to LKML but it seems I did a bad job
of breaking into granular patches.

>
> >   }
> >
> >   static void plic_irq_enable(struct irq_data *d)
> >   {
> > -     plic_irq_toggle(d, 1);
> > +     plic_irq_toggle(irq_data_get_affinity_mask(d), d->hwirq, 1);
> >   }
> >
> >   static void plic_irq_disable(struct irq_data *d)
> >   {
> > -     plic_irq_toggle(d, 0);
> > +     plic_irq_toggle(irq_data_get_affinity_mask(d), d->hwirq, 0);
> >   }
> >
> >   static struct irq_chip plic_chip = {
> > @@ -127,8 +130,6 @@ static const struct irq_domain_ops plic_irqdomain_ops = {
> >       .xlate          = irq_domain_xlate_onecell,
> >   };
> >
> > -static struct irq_domain *plic_irqdomain;
> > -
> >   /*
> >    * Handling an interrupt is a two-step process: first you claim the interrupt
> >    * by reading the claim register, then you complete the interrupt by writing
> > @@ -145,7 +146,7 @@ static void plic_handle_irq(struct pt_regs *regs)
> >
> >       csr_clear(sie, SIE_SEIE);
> >       while ((hwirq = readl(claim))) {
> > -             int irq = irq_find_mapping(plic_irqdomain, hwirq);
> > +             int irq = irq_find_mapping(plic.irqdomain, hwirq);
> >
> >               if (unlikely(irq <= 0))
> >                       pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
> > @@ -174,36 +175,34 @@ static int plic_find_hart_id(struct device_node *node)
> >   static int __init plic_init(struct device_node *node,
> >               struct device_node *parent)
> >   {
> > -     int error = 0, nr_handlers, nr_mapped = 0, i;
> > -     u32 nr_irqs;
> > +     int error = 0, i;
> >
> > -     if (plic_regs) {
> > +     if (plic.regs) {
> >               pr_warn("PLIC already present.\n");
> >               return -ENXIO;
> >       }
> >
> > -     plic_regs = of_iomap(node, 0);
> > -     if (WARN_ON(!plic_regs))
> > +     plic.regs = of_iomap(node, 0);
> > +     if (WARN_ON(!plic.regs))
> >               return -EIO;
> >
> >       error = -EINVAL;
> > -     of_property_read_u32(node, "riscv,ndev", &nr_irqs);
> > -     if (WARN_ON(!nr_irqs))
> > +     of_property_read_u32(node, "riscv,ndev", &plic.nr_irqs);
> > +     if (WARN_ON(!plic.nr_irqs))
> >               goto out_iounmap;
> >
> > -     nr_handlers = of_irq_count(node);
> > -     if (WARN_ON(!nr_handlers))
> > +     plic.nr_handlers = of_irq_count(node);
> > +     if (WARN_ON(!plic.nr_handlers))
> >               goto out_iounmap;
> > -     if (WARN_ON(nr_handlers < num_possible_cpus()))
> > +     if (WARN_ON(plic.nr_handlers < num_possible_cpus()))
> >               goto out_iounmap;
> >
> > -     error = -ENOMEM;
> > -     plic_irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
> > -                     &plic_irqdomain_ops, NULL);
> > -     if (WARN_ON(!plic_irqdomain))
> > +     plic.irqdomain = irq_domain_add_linear(node, plic.nr_irqs + 1,
> > +                                             &plic_irqdomain_ops, NULL);
> > +     if (WARN_ON(!plic.irqdomain))
> >               goto out_iounmap;
> >
>
> Should we return EINVAL if irq_domain_add_linear fails ? Earlier, it was
> returning ENOMEM.

Sure, I will update this.

>
> > -     for (i = 0; i < nr_handlers; i++) {
> > +     for (i = 0; i < plic.nr_handlers; i++) {
> >               struct of_phandle_args parent;
> >               struct plic_handler *handler;
> >               irq_hw_number_t hwirq;
> > @@ -227,27 +226,27 @@ static int __init plic_init(struct device_node *node,
> >               cpu = riscv_hartid_to_cpuid(hartid);
> >               handler = per_cpu_ptr(&plic_handlers, cpu);
> >               handler->present = true;
> > -             handler->ctxid = i;
>
>
> The previous patch removed all the usage of ctxid. So this line also can
> be included in that patch as well to make it more coherent.

Sure, I will move it to previous patch.

Thanks for the detailed review.

Regards,
Anup