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Subject[RFC PATCH v2 3/5] irq: gic: Add support for NMI routing
Date
This patch provides an implementation of irq_set_nmi_routing by
allowing SPIs to be switched between group 1 (IRQ) and group 0 (FIQ).

It also repaces the interface used between the default FIQ handler and
the GIC. These extensions are required in order to allow SPIs to be
acknowledged and completed.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
---
arch/arm/kernel/traps.c | 29 +++++++++++++++----
drivers/irqchip/irq-gic.c | 64 +++++++++++++++++++++++++++++------------
include/linux/irqchip/arm-gic.h | 6 +++-
3 files changed, 74 insertions(+), 25 deletions(-)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 5645f81ac4cc..445fdf26b1af 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -26,6 +26,7 @@
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/irq.h>
+#include <linux/interrupt.h>
#include <linux/irqchip/arm-gic.h>

#include <linux/atomic.h>
@@ -462,6 +463,23 @@ die_sig:
arm_notify_die("Oops - undefined instruction", regs, &info, 0, 6);
}

+int arch_filter_nmi_handler(irq_handler_t handler)
+{
+ irq_handler_t whitelist[] = {
+ };
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(whitelist); i++)
+ if (handler == whitelist[i]) {
+ pr_debug("%pS accepted for use as NMI handler\n",
+ handler);
+ return 0;
+ }
+
+ pr_err("%pS cannot be used as an NMI handler\n", handler);
+ return -EPERM;
+}
+
/*
* Handle FIQ similarly to NMI on x86 systems.
*
@@ -478,19 +496,20 @@ asmlinkage void __exception_irq_entry handle_fiq_as_nmi(struct pt_regs *regs)
{
unsigned int cpu = smp_processor_id();
struct pt_regs *old_regs = set_irq_regs(regs);
+ enum irqreturn irqret = 0;

__inc_irq_stat(cpu, __nmi_count);
nmi_enter();

-#ifdef CONFIG_ARM_GIC
- gic_handle_fiq_ipi();
-#endif
+ irqret = gic_handle_fiq();
+
+ if (irqret == IRQ_NONE) {
#ifdef CONFIG_SMP
- ipi_cpu_backtrace(regs);
+ ipi_cpu_backtrace(regs);
#endif
+ }

nmi_exit();
-
set_irq_regs(old_regs);
}

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index c4f4a8827ed8..658c6dd5cf08 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -129,6 +129,9 @@ struct irq_chip gic_arch_extn = {

static struct gic_chip_data gic_data[MAX_GIC_NR] __read_mostly;

+static int gic_set_group_irq(struct gic_chip_data *gic, unsigned int hwirq,
+ int group);
+
#ifdef CONFIG_GIC_NON_BANKED
static void __iomem *gic_get_percpu_base(union gic_base *base)
{
@@ -214,6 +217,18 @@ static void gic_eoi_irq(struct irq_data *d)
writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
}

+static int gic_set_nmi_routing(struct irq_data *d, unsigned int nmi)
+{
+ struct gic_chip_data *gic = irq_data_get_irq_chip_data(d);
+ int ret;
+
+ ret = gic_set_group_irq(gic, gic_irq(d), !nmi);
+ if (ret >= 0)
+ ret = !ret;
+
+ return ret;
+}
+
static int gic_set_type(struct irq_data *d, unsigned int type)
{
void __iomem *base = gic_dist_base(d);
@@ -346,6 +361,7 @@ static struct irq_chip gic_chip = {
.irq_mask = gic_mask_irq,
.irq_unmask = gic_unmask_irq,
.irq_eoi = gic_eoi_irq,
+ .irq_set_nmi_routing = gic_set_nmi_routing,
.irq_set_type = gic_set_type,
.irq_retrigger = gic_retrigger,
#ifdef CONFIG_SMP
@@ -364,8 +380,8 @@ static struct irq_chip gic_chip = {
* If is safe to call this function on systems which do not support
* grouping (it will have no effect).
*/
-static void gic_set_group_irq(struct gic_chip_data *gic, unsigned int hwirq,
- int group)
+static int gic_set_group_irq(struct gic_chip_data *gic, unsigned int hwirq,
+ int group)
{
void __iomem *base = gic_data_dist_base(gic);
unsigned int grp_reg = hwirq / 32 * 4;
@@ -381,7 +397,7 @@ static void gic_set_group_irq(struct gic_chip_data *gic, unsigned int hwirq,
* the EnableGrp1 bit set.
*/
if (!(GICD_ENABLE_GRP1 & readl_relaxed(base + GIC_DIST_CTRL)))
- return;
+ return -EINVAL;

raw_spin_lock(&irq_controller_lock);

@@ -403,32 +419,42 @@ static void gic_set_group_irq(struct gic_chip_data *gic, unsigned int hwirq,
writel_relaxed(pri_val, base + GIC_DIST_PRI + pri_reg);

raw_spin_unlock(&irq_controller_lock);
-}

+ return group;
+}

-/*
- * Fully acknowledge (both ack and eoi) any outstanding FIQ-based IPI,
- * otherwise do nothing.
- */
-void gic_handle_fiq_ipi(void)
+enum irqreturn gic_handle_fiq(void)
{
struct gic_chip_data *gic = &gic_data[0];
void __iomem *cpu_base = gic_data_cpu_base(gic);
- unsigned long irqstat, irqnr;
+ unsigned long irqstat, hwirq;
+ unsigned int irq = 0;
+
+ /*
+ * This function is called unconditionally by the default FIQ
+ * handler so first we must check that the driver it
+ * initialized.
+ */
+ if (!gic->gic_irqs)
+ return IRQ_NONE;

if (WARN_ON(!in_nmi()))
- return;
+ return IRQ_NONE;

- while ((1u << readl_relaxed(cpu_base + GIC_CPU_HIGHPRI)) &
- SMP_IPI_FIQ_MASK) {
- irqstat = readl_relaxed(cpu_base + GIC_CPU_INTACK);
- writel_relaxed(irqstat, cpu_base + GIC_CPU_EOI);
+ /* read intack with the priority mask set so we only acknowledge FIQs */
+ writel_relaxed(GICC_INT_PRI_THRESHOLD >> 1, cpu_base + GIC_CPU_PRIMASK);
+ irqstat = readl_relaxed(cpu_base + GIC_CPU_INTACK);
+ writel_relaxed(GICC_INT_PRI_THRESHOLD, cpu_base + GIC_CPU_PRIMASK);

- irqnr = irqstat & GICC_IAR_INT_ID_MASK;
- WARN_RATELIMIT(irqnr > 16,
- "Unexpected irqnr %lu (bad prioritization?)\n",
- irqnr);
+ hwirq = irqstat & GICC_IAR_INT_ID_MASK;
+ if (likely(hwirq > 15 && hwirq < 1021)) {
+ irq = irq_find_mapping(gic->domain, hwirq);
+ handle_nmi_irq(irq);
}
+
+ writel_relaxed(irqstat, gic_data_cpu_base(gic) + GIC_CPU_EOI);
+
+ return IRQ_RETVAL(irq);
}

void __init gic_cascade_irq(unsigned int gic_nr, unsigned int irq)
diff --git a/include/linux/irqchip/arm-gic.h b/include/linux/irqchip/arm-gic.h
index 7690f70049a3..265ea31a5711 100644
--- a/include/linux/irqchip/arm-gic.h
+++ b/include/linux/irqchip/arm-gic.h
@@ -127,7 +127,11 @@ static inline void __init register_routable_domain_ops
gic_routable_irq_domain_ops = ops;
}

-void gic_handle_fiq_ipi(void);
+#ifdef CONFIG_ARM_GIC
+enum irqreturn gic_handle_fiq(void);
+#else
+enum irqreturn gic_handle_fiq(void) { return IRQ_NONE; }
+#endif

#endif /* __ASSEMBLY */
#endif
--
1.9.3


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