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Merge branch irq/ipi-mux into irq/irqchip-next
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* irq/ipi-mux:
  : .
  : Extract the IPI muxing facility from the Apple AIC driver and
  : move it over to core code. The riscv irqchip code will eventually
  : make use of this.
  : .
  genirq/ipi-mux: Use irq_domain_alloc_irqs()
  irqchip/apple-aic: Move over to core ipi-mux
  genirq: Add mechanism to multiplex a single HW IPI

Signed-off-by: Marc Zyngier <maz@kernel.org>
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Marc Zyngier committed Feb 6, 2023
2 parents 5dc4c99 + 3d812a0 commit 6360ec8
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Showing 6 changed files with 224 additions and 153 deletions.
1 change: 1 addition & 0 deletions drivers/irqchip/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -658,6 +658,7 @@ config APPLE_AIC
bool "Apple Interrupt Controller (AIC)"
depends on ARM64
depends on ARCH_APPLE || COMPILE_TEST
select GENERIC_IRQ_IPI_MUX
help
Support for the Apple Interrupt Controller found on Apple Silicon SoCs,
such as the M1.
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161 changes: 8 additions & 153 deletions drivers/irqchip/irq-apple-aic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -292,7 +292,6 @@ struct aic_irq_chip {
void __iomem *base;
void __iomem *event;
struct irq_domain *hw_domain;
struct irq_domain *ipi_domain;
struct {
cpumask_t aff;
} *fiq_aff[AIC_NR_FIQ];
Expand All @@ -307,9 +306,6 @@ struct aic_irq_chip {

static DEFINE_PER_CPU(uint32_t, aic_fiq_unmasked);

static DEFINE_PER_CPU(atomic_t, aic_vipi_flag);
static DEFINE_PER_CPU(atomic_t, aic_vipi_enable);

static struct aic_irq_chip *aic_irqc;

static void aic_handle_ipi(struct pt_regs *regs);
Expand Down Expand Up @@ -751,98 +747,8 @@ static void aic_ipi_send_fast(int cpu)
isb();
}

static void aic_ipi_mask(struct irq_data *d)
{
u32 irq_bit = BIT(irqd_to_hwirq(d));

/* No specific ordering requirements needed here. */
atomic_andnot(irq_bit, this_cpu_ptr(&aic_vipi_enable));
}

static void aic_ipi_unmask(struct irq_data *d)
{
struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
u32 irq_bit = BIT(irqd_to_hwirq(d));

atomic_or(irq_bit, this_cpu_ptr(&aic_vipi_enable));

/*
* The atomic_or() above must complete before the atomic_read()
* below to avoid racing aic_ipi_send_mask().
*/
smp_mb__after_atomic();

/*
* If a pending vIPI was unmasked, raise a HW IPI to ourselves.
* No barriers needed here since this is a self-IPI.
*/
if (atomic_read(this_cpu_ptr(&aic_vipi_flag)) & irq_bit) {
if (static_branch_likely(&use_fast_ipi))
aic_ipi_send_fast(smp_processor_id());
else
aic_ic_write(ic, AIC_IPI_SEND, AIC_IPI_SEND_CPU(smp_processor_id()));
}
}

static void aic_ipi_send_mask(struct irq_data *d, const struct cpumask *mask)
{
struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
u32 irq_bit = BIT(irqd_to_hwirq(d));
u32 send = 0;
int cpu;
unsigned long pending;

for_each_cpu(cpu, mask) {
/*
* This sequence is the mirror of the one in aic_ipi_unmask();
* see the comment there. Additionally, release semantics
* ensure that the vIPI flag set is ordered after any shared
* memory accesses that precede it. This therefore also pairs
* with the atomic_fetch_andnot in aic_handle_ipi().
*/
pending = atomic_fetch_or_release(irq_bit, per_cpu_ptr(&aic_vipi_flag, cpu));

/*
* The atomic_fetch_or_release() above must complete before the
* atomic_read() below to avoid racing aic_ipi_unmask().
*/
smp_mb__after_atomic();

if (!(pending & irq_bit) &&
(atomic_read(per_cpu_ptr(&aic_vipi_enable, cpu)) & irq_bit)) {
if (static_branch_likely(&use_fast_ipi))
aic_ipi_send_fast(cpu);
else
send |= AIC_IPI_SEND_CPU(cpu);
}
}

/*
* The flag writes must complete before the physical IPI is issued
* to another CPU. This is implied by the control dependency on
* the result of atomic_read_acquire() above, which is itself
* already ordered after the vIPI flag write.
*/
if (send)
aic_ic_write(ic, AIC_IPI_SEND, send);
}

static struct irq_chip ipi_chip = {
.name = "AIC-IPI",
.irq_mask = aic_ipi_mask,
.irq_unmask = aic_ipi_unmask,
.ipi_send_mask = aic_ipi_send_mask,
};

/*
* IPI IRQ domain
*/

static void aic_handle_ipi(struct pt_regs *regs)
{
int i;
unsigned long enabled, firing;

/*
* Ack the IPI. We need to order this after the AIC event read, but
* that is enforced by normal MMIO ordering guarantees.
Expand All @@ -857,27 +763,7 @@ static void aic_handle_ipi(struct pt_regs *regs)
aic_ic_write(aic_irqc, AIC_IPI_ACK, AIC_IPI_OTHER);
}

/*
* The mask read does not need to be ordered. Only we can change
* our own mask anyway, so no races are possible here, as long as
* we are properly in the interrupt handler (which is covered by
* the barrier that is part of the top-level AIC handler's readl()).
*/
enabled = atomic_read(this_cpu_ptr(&aic_vipi_enable));

/*
* Clear the IPIs we are about to handle. This pairs with the
* atomic_fetch_or_release() in aic_ipi_send_mask(), and needs to be
* ordered after the aic_ic_write() above (to avoid dropping vIPIs) and
* before IPI handling code (to avoid races handling vIPIs before they
* are signaled). The former is taken care of by the release semantics
* of the write portion, while the latter is taken care of by the
* acquire semantics of the read portion.
*/
firing = atomic_fetch_andnot(enabled, this_cpu_ptr(&aic_vipi_flag)) & enabled;

for_each_set_bit(i, &firing, AIC_NR_SWIPI)
generic_handle_domain_irq(aic_irqc->ipi_domain, i);
ipi_mux_process();

/*
* No ordering needed here; at worst this just changes the timing of
Expand All @@ -887,55 +773,24 @@ static void aic_handle_ipi(struct pt_regs *regs)
aic_ic_write(aic_irqc, AIC_IPI_MASK_CLR, AIC_IPI_OTHER);
}

static int aic_ipi_alloc(struct irq_domain *d, unsigned int virq,
unsigned int nr_irqs, void *args)
static void aic_ipi_send_single(unsigned int cpu)
{
int i;

for (i = 0; i < nr_irqs; i++) {
irq_set_percpu_devid(virq + i);
irq_domain_set_info(d, virq + i, i, &ipi_chip, d->host_data,
handle_percpu_devid_irq, NULL, NULL);
}

return 0;
}

static void aic_ipi_free(struct irq_domain *d, unsigned int virq, unsigned int nr_irqs)
{
/* Not freeing IPIs */
if (static_branch_likely(&use_fast_ipi))
aic_ipi_send_fast(cpu);
else
aic_ic_write(aic_irqc, AIC_IPI_SEND, AIC_IPI_SEND_CPU(cpu));
}

static const struct irq_domain_ops aic_ipi_domain_ops = {
.alloc = aic_ipi_alloc,
.free = aic_ipi_free,
};

static int __init aic_init_smp(struct aic_irq_chip *irqc, struct device_node *node)
{
struct irq_domain *ipi_domain;
int base_ipi;

ipi_domain = irq_domain_create_linear(irqc->hw_domain->fwnode, AIC_NR_SWIPI,
&aic_ipi_domain_ops, irqc);
if (WARN_ON(!ipi_domain))
return -ENODEV;

ipi_domain->flags |= IRQ_DOMAIN_FLAG_IPI_SINGLE;
irq_domain_update_bus_token(ipi_domain, DOMAIN_BUS_IPI);

base_ipi = __irq_domain_alloc_irqs(ipi_domain, -1, AIC_NR_SWIPI,
NUMA_NO_NODE, NULL, false, NULL);

if (WARN_ON(!base_ipi)) {
irq_domain_remove(ipi_domain);
base_ipi = ipi_mux_create(AIC_NR_SWIPI, aic_ipi_send_single);
if (WARN_ON(base_ipi <= 0))
return -ENODEV;
}

set_smp_ipi_range(base_ipi, AIC_NR_SWIPI);

irqc->ipi_domain = ipi_domain;

return 0;
}

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3 changes: 3 additions & 0 deletions include/linux/irq.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1266,6 +1266,9 @@ int __ipi_send_mask(struct irq_desc *desc, const struct cpumask *dest);
int ipi_send_single(unsigned int virq, unsigned int cpu);
int ipi_send_mask(unsigned int virq, const struct cpumask *dest);

void ipi_mux_process(void);
int ipi_mux_create(unsigned int nr_ipi, void (*mux_send)(unsigned int cpu));

#ifdef CONFIG_GENERIC_IRQ_MULTI_HANDLER
/*
* Registers a generic IRQ handling function as the top-level IRQ handler in
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5 changes: 5 additions & 0 deletions kernel/irq/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,11 @@ config GENERIC_IRQ_IPI
depends on SMP
select IRQ_DOMAIN_HIERARCHY

# Generic IRQ IPI Mux support
config GENERIC_IRQ_IPI_MUX
bool
depends on SMP

# Generic MSI hierarchical interrupt domain support
config GENERIC_MSI_IRQ
bool
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1 change: 1 addition & 0 deletions kernel/irq/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ obj-$(CONFIG_GENERIC_IRQ_MIGRATION) += cpuhotplug.o
obj-$(CONFIG_PM_SLEEP) += pm.o
obj-$(CONFIG_GENERIC_MSI_IRQ) += msi.o
obj-$(CONFIG_GENERIC_IRQ_IPI) += ipi.o
obj-$(CONFIG_GENERIC_IRQ_IPI_MUX) += ipi-mux.o
obj-$(CONFIG_SMP) += affinity.o
obj-$(CONFIG_GENERIC_IRQ_DEBUGFS) += debugfs.o
obj-$(CONFIG_GENERIC_IRQ_MATRIX_ALLOCATOR) += matrix.o
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