linux-kernel - Re: [PATCH v2 1/4] irqchip: sifive-plic: Pre-compute context hart base and enable base

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Date:   Fri, 30 Nov 2018 09:04:46 +0530
From:   Anup Patel <anup@...infault.org>
To:     Atish Patra <atish.patra@....com>
Cc:     Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoph Hellwig <hch@...radead.org>,
        linux-riscv@...ts.infradead.org,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] irqchip: sifive-plic: Pre-compute context hart
 base and enable base

On Fri, Nov 30, 2018 at 6:05 AM Atish Patra <atish.patra@....com> wrote:
>
> On 11/27/18 2:03 AM, Anup Patel wrote:
> > This patch does following optimizations:
> > 1. Pre-compute hart base for each context handler
> > 2. Pre-compute enable base for each context handler
> > 3. Have enable lock for each context handler instead
> > of global plic_toggle_lock
> >
> > Signed-off-by: Anup Patel <anup@...infault.org>
> > ---
> >   drivers/irqchip/irq-sifive-plic.c | 41 +++++++++++++------------------
> >   1 file changed, 17 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> > index 357e9daf94ae..56fce648a901 100644
> > --- a/drivers/irqchip/irq-sifive-plic.c
> > +++ b/drivers/irqchip/irq-sifive-plic.c
> > @@ -60,36 +60,24 @@ 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;
>
> It should be u32. Otherwise, plic_toggle calculates incorrect address
> and it does not boot on Unlheased.

Good catch. I did not see this issue on QEMU because we have
very IRQs over there.

>
> >   };
> >   static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
> >
> > -static inline void __iomem *plic_hart_offset(int ctxid)
> > +static inline void plic_toggle(struct plic_handler *handler,
> > +                             int hwirq, int enable)
> >   {
> > -     return plic_regs + CONTEXT_BASE + ctxid * CONTEXT_PER_HART;
> > -}
> > -
> > -static inline u32 __iomem *plic_enable_base(int ctxid)
> > -{
> > -     return plic_regs + ENABLE_BASE + ctxid * ENABLE_PER_HART;
> > -}
> > -
> > -/*
> > - * Protect mask operations on the registers given that we can't assume that
> > - * atomic memory operations work on them.
> > - */
>
> Should we keep the comment for enable_lock ?

Sure, I will retain the comment for enable_lock.

>
> > -static DEFINE_RAW_SPINLOCK(plic_toggle_lock);
> > -
> > -static inline void plic_toggle(int ctxid, int hwirq, int enable)
> > -{
> > -     u32 __iomem *reg = plic_enable_base(ctxid) + (hwirq / 32);
> > +     u32 __iomem *reg = handler->enable_base + (hwirq / 32);
> >       u32 hwirq_mask = 1 << (hwirq % 32);
> >
> > -     raw_spin_lock(&plic_toggle_lock);
> > +     raw_spin_lock(&handler->enable_lock);
> >       if (enable)
> >               writel(readl(reg) | hwirq_mask, reg);
> >       else
> >               writel(readl(reg) & ~hwirq_mask, reg);
> > -     raw_spin_unlock(&plic_toggle_lock);
> > +     raw_spin_unlock(&handler->enable_lock);
> >   }
> >
> >   static inline void plic_irq_toggle(struct irq_data *d, int enable)
> > @@ -101,7 +89,7 @@ static inline void plic_irq_toggle(struct irq_data *d, int enable)
> >               struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
> >
> >               if (handler->present)
> > -                     plic_toggle(handler->ctxid, d->hwirq, enable);
> > +                     plic_toggle(handler, d->hwirq, enable);
> >       }
> >   }
> >
> > @@ -150,7 +138,7 @@ static struct irq_domain *plic_irqdomain;
> >   static void plic_handle_irq(struct pt_regs *regs)
> >   {
> >       struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
> > -     void __iomem *claim = plic_hart_offset(handler->ctxid) + CONTEXT_CLAIM;
> > +     void __iomem *claim = handler->hart_base + CONTEXT_CLAIM;
> >       irq_hw_number_t hwirq;
> >
> >       WARN_ON_ONCE(!handler->present);
> > @@ -240,11 +228,16 @@ static int __init plic_init(struct device_node *node,
> >               handler = per_cpu_ptr(&plic_handlers, cpu);
> >               handler->present = true;
> >               handler->ctxid = i;
> > +             handler->hart_base =
> > +                     plic_regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
> > +             raw_spin_lock_init(&handler->enable_lock);
> > +             handler->enable_base =
> > +                     plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
> >
> >               /* priority must be > threshold to trigger an interrupt */
> > -             writel(0, plic_hart_offset(i) + CONTEXT_THRESHOLD);
> > +             writel(0, handler->hart_base + CONTEXT_THRESHOLD);
> >               for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
> > -                     plic_toggle(i, hwirq, 0);
> > +                     plic_toggle(handler, hwirq, 0);
> >               nr_mapped++;
> >       }
> >
> >
>

--
Anup