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Date:	Mon, 30 Jun 2014 20:09:18 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Anup Patel <anup@...infault.org>
CC:	Marc Zyngier <marc.zyngier@....com>,
	"kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <will.deacon@....com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Eric Auger <eric.auger@...aro.org>,
	Ian Campbell <ian.campbell@...rix.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: Re: [RFC PATCH 3/9] irqchip: GIC: Convert to EOImode == 1

On Wed, 25 Jun 2014, Anup Patel wrote:
> Hi Marc,
> 
> On Wed, Jun 25, 2014 at 2:58 PM, Marc Zyngier <marc.zyngier@....com> wrote:
> > So far, GICv2 has been used in with EOImode == 0. The effect of this
> > mode is to perform the priority drop and the deactivation of the
> > interrupt at the same time.
> >
> > While this works perfectly for Linux (we only have a single priority),
> > it causes issues when an interrupt is forwarded to a guest, and when
> > we want the guest to perform the EOI itself.
> >
> > For this case, the GIC architecture provides EOImode == 1, where:
> > - A write to the EOI register drops the priority of the interrupt and leaves
> > it active. Other interrupts at the same priority level can now be taken,
> > but the active interrupt cannot be taken again
> > - A write to the DIR marks the interrupt as inactive, meaning it can
> > now be taken again.
> >
> > We only enable this feature when booted in HYP mode. Also, as most device
> > trees are broken (they report the CPU interface size to be 4kB, while
> > the GICv2 CPU interface size is 8kB), output a warning if we're booted
> > in HYP mode, and disable the feature.
> >
> > Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> > ---
> >  drivers/irqchip/irq-gic.c       | 61 +++++++++++++++++++++++++++++++++++++----
> >  include/linux/irqchip/arm-gic.h |  4 +++
> >  2 files changed, 59 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> > index 508b815..9295bf2 100644
> > --- a/drivers/irqchip/irq-gic.c
> > +++ b/drivers/irqchip/irq-gic.c
> > @@ -45,6 +45,7 @@
> >  #include <asm/irq.h>
> >  #include <asm/exception.h>
> >  #include <asm/smp_plat.h>
> > +#include <asm/virt.h>
> >
> >  #include "irq-gic-common.h"
> >  #include "irqchip.h"
> > @@ -94,6 +95,10 @@ struct irq_chip gic_arch_extn = {
> >         .irq_set_wake   = NULL,
> >  };
> >
> > +static struct irq_chip *gic_chip;
> > +
> > +static bool supports_deactivate = false;
> > +
> >  #ifndef MAX_GIC_NR
> >  #define MAX_GIC_NR     1
> >  #endif
> > @@ -185,6 +190,12 @@ static void gic_eoi_irq(struct irq_data *d)
> >         writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
> >  }
> >
> > +static void gic_eoi_dir_irq(struct irq_data *d)
> > +{
> > +       gic_eoi_irq(d);
> > +       writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_DEACTIVATE);
> > +}

Would it be better if you moved the gic_eoi_irq call earlier? Maybe
somewhere in gic_handle_irq?


> >  static int gic_set_type(struct irq_data *d, unsigned int type)
> >  {
> >         void __iomem *base = gic_dist_base(d);
> > @@ -277,6 +288,7 @@ static void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
> >                 }
> >                 if (irqnr < 16) {
> >                         writel_relaxed(irqstat, cpu_base + GIC_CPU_EOI);
> > +                       writel_relaxed(irqstat, cpu_base + GIC_CPU_DEACTIVATE);
> >  #ifdef CONFIG_SMP
> >                         handle_IPI(irqnr, regs);
> >  #endif
> > @@ -313,7 +325,7 @@ static void gic_handle_cascade_irq(unsigned int irq, struct irq_desc *desc)
> >         chained_irq_exit(chip, desc);
> >  }
> >
> > -static struct irq_chip gic_chip = {
> > +static struct irq_chip gicv1_chip = {
> >         .name                   = "GIC",
> >         .irq_mask               = gic_mask_irq,
> >         .irq_unmask             = gic_unmask_irq,
> > @@ -326,6 +338,19 @@ static struct irq_chip gic_chip = {
> >         .irq_set_wake           = gic_set_wake,
> >  };
> >
> > +static struct irq_chip gicv2_chip = {
> > +       .name                   = "GIC",
> > +       .irq_mask               = gic_mask_irq,
> > +       .irq_unmask             = gic_unmask_irq,
> > +       .irq_eoi                = gic_eoi_dir_irq,
> > +       .irq_set_type           = gic_set_type,
> > +       .irq_retrigger          = gic_retrigger,
> > +#ifdef CONFIG_SMP
> > +       .irq_set_affinity       = gic_set_affinity,
> > +#endif
> > +       .irq_set_wake           = gic_set_wake,
> > +};
> > +
> >  void __init gic_cascade_irq(unsigned int gic_nr, unsigned int irq)
> >  {
> >         if (gic_nr >= MAX_GIC_NR)
> > @@ -377,6 +402,16 @@ static void __init gic_dist_init(struct gic_chip_data *gic)
> >         writel_relaxed(1, base + GIC_DIST_CTRL);
> >  }
> >
> > +static void gic_cpu_if_up(void)
> > +{
> > +       void __iomem *cpu_base = gic_data_cpu_base(&gic_data[0]);
> > +       u32 val = 0;
> > +
> > +       if (supports_deactivate)
> > +               val = GIC_CPU_CTRL_EOImodeNS;
> > +       writel_relaxed(val | 1, cpu_base + GIC_CPU_CTRL);
> > +}
> > +
> >  static void gic_cpu_init(struct gic_chip_data *gic)
> >  {
> >         void __iomem *dist_base = gic_data_dist_base(gic);
> > @@ -402,7 +437,7 @@ static void gic_cpu_init(struct gic_chip_data *gic)
> >         gic_cpu_config(dist_base, NULL);
> >
> >         writel_relaxed(0xf0, base + GIC_CPU_PRIMASK);
> > -       writel_relaxed(1, base + GIC_CPU_CTRL);
> > +       gic_cpu_if_up();
> >  }
> >
> >  void gic_cpu_if_down(void)
> > @@ -543,7 +578,7 @@ static void gic_cpu_restore(unsigned int gic_nr)
> >                 writel_relaxed(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4);
> >
> >         writel_relaxed(0xf0, cpu_base + GIC_CPU_PRIMASK);
> > -       writel_relaxed(1, cpu_base + GIC_CPU_CTRL);
> > +       gic_cpu_if_up();
> >  }
> >
> >  static int gic_notifier(struct notifier_block *self, unsigned long cmd,        void *v)
> > @@ -770,11 +805,11 @@ static int gic_irq_domain_map(struct irq_domain *d, unsigned int irq,
> >  {
> >         if (hw < 32) {
> >                 irq_set_percpu_devid(irq);
> > -               irq_set_chip_and_handler(irq, &gic_chip,
> > +               irq_set_chip_and_handler(irq, gic_chip,
> >                                          handle_percpu_devid_irq);
> >                 set_irq_flags(irq, IRQF_VALID | IRQF_NOAUTOEN);
> >         } else {
> > -               irq_set_chip_and_handler(irq, &gic_chip,
> > +               irq_set_chip_and_handler(irq, gic_chip,
> >                                          handle_fasteoi_irq);
> >                 set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
> >
> > @@ -951,6 +986,11 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
> >
> >         gic_irqs -= hwirq_base; /* calculate # of irqs to allocate */
> >
> > +       if (!supports_deactivate)
> > +               gic_chip = &gicv1_chip;
> > +       else
> > +               gic_chip = &gicv2_chip;
> > +
> >         if (of_property_read_u32(node, "arm,routable-irqs",
> >                                  &nr_routable_irqs)) {
> >                 irq_base = irq_alloc_descs(irq_start, 16, gic_irqs,
> > @@ -980,7 +1020,7 @@ void __init gic_init_bases(unsigned int gic_nr, int irq_start,
> >                 set_handle_irq(gic_handle_irq);
> >         }
> >
> > -       gic_chip.flags |= gic_arch_extn.flags;
> > +       gic_chip->flags |= gic_arch_extn.flags;
> >         gic_dist_init(gic);
> >         gic_cpu_init(gic);
> >         gic_pm_init(gic);
> > @@ -994,6 +1034,7 @@ gic_of_init(struct device_node *node, struct device_node *parent)
> >  {
> >         void __iomem *cpu_base;
> >         void __iomem *dist_base;
> > +       struct resource cu_res;
> >         u32 percpu_offset;
> >         int irq;
> >
> > @@ -1006,6 +1047,14 @@ gic_of_init(struct device_node *node, struct device_node *parent)
> >         cpu_base = of_iomap(node, 1);
> >         WARN(!cpu_base, "unable to map gic cpu registers\n");
> >
> > +       of_address_to_resource(node, 1, &cpu_res);
> > +       if (is_hyp_mode_available()) {
> 
> Interrupt deactivation feature is not dependent on whether
> hyp-mode is available or not.
> 
> We can use GICC_DIR even if CPU does not have
> virtualization extension. Also, we can use GICV_DIR
> when running as Guest or VM.
> 
> I think "supports_deactivate" should depend on
> the GIC compatible string.
> 
> > +               if (resource_size(&cpu_res) >= SZ_8K)
> > +                       supports_deactivate = true;
> > +               else
> > +                       pr_warn("GIC: CPU interface size is %x, DT is probably wrong\n", (int)resource_size(&cpu_res));
> 
> This will not work on APM X-Gene because, for
> X-Gene first CPU page is at 0x78020000 and
> second CPU page is at 0x78030000.
> 
> Ian had send-out a patch long time back to extend
> GIC dt-bindings for addressing this issue.
> (http://www.spinics.net/lists/arm-kernel/msg283767.html)
> 
> Regards,
> Anup
> 
> > +       }
> > +
> >         if (of_property_read_u32(node, "cpu-offset", &percpu_offset))
> >                 percpu_offset = 0;
> >
> > diff --git a/include/linux/irqchip/arm-gic.h b/include/linux/irqchip/arm-gic.h
> > index 45e2d8c..ffe3911 100644
> > --- a/include/linux/irqchip/arm-gic.h
> > +++ b/include/linux/irqchip/arm-gic.h
> > @@ -21,6 +21,10 @@
> >  #define GIC_CPU_ACTIVEPRIO             0xd0
> >  #define GIC_CPU_IDENT                  0xfc
> >
> > +#define GIC_CPU_DEACTIVATE             0x1000
> > +
> > +#define GIC_CPU_CTRL_EOImodeNS         (1 << 9)
> > +
> >  #define GICC_IAR_INT_ID_MASK           0x3ff
> >
> >  #define GIC_DIST_CTRL                  0x000
> > --
> > 1.8.3.4
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 
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