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Subject[PATCH 16/18] irqchip/apple-aic: Add SMP / IPI support
Date
Since the hardware IRQ controller only supports two IPIs per CPU and
Linux needs more, we implement 32 virtual IPIs using software and funnel
them through a single hardware IPI.

Signed-off-by: Hector Martin <marcan@marcan.st>
---
drivers/irqchip/irq-apple-aic.c | 195 +++++++++++++++++++++++++++++++-
1 file changed, 190 insertions(+), 5 deletions(-)

diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
index 533e3ce9f432..daeffcca67ca 100644
--- a/drivers/irqchip/irq-apple-aic.c
+++ b/drivers/irqchip/irq-apple-aic.c
@@ -26,7 +26,9 @@
*
* Implementation notes:
*
- * - This driver creates one IRQ domain for HW IRQs and the timer FIQs
+ * - This driver creates two IRQ domains, one for HW IRQs and the timer FIQs, and one for IPIs
+ * - Since Linux needs more than 2 IPIs, we implement a software IRQ controller and funnel all IPIs
+ * into one per-CPU IPI (the second "self" IPI is unused).
* - FIQ hwirq numbers are assigned after true hwirqs, and are per-cpu
* - DT bindings use 3-cell form (like GIC):
* - <0 nr flags> - hwirq #nr
@@ -34,8 +36,8 @@
* - nr=0 physical timer
* - nr=1 virtual timer
* - <2 nr flags> - IPI #nr
- * - nr=0 other IPI
- * - nr=1 self IPI
+ * - nr=0 other IPI (used internally for the virtual IPIs)
+ * - nr=1 self IPI (unused)
*
*/

@@ -91,6 +93,7 @@

#define AIC_NR_FIQ 2
#define AIC_NR_IPI 2
+#define AIC_NR_SWIPI 32

/*
* Max 31 bits in IPI SEND register (top bit is self).
@@ -101,9 +104,14 @@
struct aic_irq_chip {
void __iomem *base;
struct irq_domain *hw_domain;
+ struct irq_domain *ipi_domain;
int nr_hw;
+ int ipi_hwirq;
};

+atomic_t aic_vipi_flag[AIC_MAX_CPUS];
+atomic_t aic_vipi_mask[AIC_MAX_CPUS];
+
static struct aic_irq_chip *aic_irqc;

static inline u32 aic_ic_read(struct aic_irq_chip *ic, u32 reg)
@@ -159,6 +167,11 @@ static void aic_handle_irq(struct pt_regs *regs)
if (type == AIC_EVENT_TYPE_HW) {
handle_domain_irq(aic_irqc->hw_domain, irq, regs);
} else if (type == AIC_EVENT_TYPE_IPI) {
+ /*
+ * Ensure loads from normal memory are ordered with respect to the wmb()
+ * in aic_ipi_send_mask().
+ */
+ rmb();
handle_domain_irq(aic_irqc->hw_domain,
ic->nr_hw + AIC_NR_FIQ + irq - 1, regs);
} else {
@@ -202,11 +215,33 @@ static void __exception_irq_entry aic_handle_irq_or_fiq(struct pt_regs *regs)
aic_handle_irq(regs);
}

+static int aic_irq_set_affinity(struct irq_data *d,
+ const struct cpumask *mask_val, bool force)
+{
+ irq_hw_number_t hwirq = irqd_to_hwirq(d);
+ struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+ int cpu;
+
+ if (hwirq > ic->nr_hw)
+ return -EINVAL;
+
+ if (force)
+ cpu = cpumask_first(mask_val);
+ else
+ cpu = cpumask_any_and(mask_val, cpu_online_mask);
+
+ aic_ic_write(ic, AIC_TARGET_CPU + hwirq * 4, BIT(cpu));
+ irq_data_update_effective_affinity(d, cpumask_of(cpu));
+
+ return IRQ_SET_MASK_OK;
+}
+
static struct irq_chip aic_chip = {
.name = "AIC",
.irq_mask = aic_irq_mask,
.irq_unmask = aic_irq_unmask,
.irq_eoi = aic_irq_eoi,
+ .irq_set_affinity = aic_irq_set_affinity,
};

static int aic_irq_domain_map(struct irq_domain *id, unsigned int irq,
@@ -264,6 +299,149 @@ static const struct irq_domain_ops aic_irq_domain_ops = {
.xlate = aic_irq_domain_xlate,
};

+static void aic_ipi_mask(struct irq_data *d)
+{
+ struct aic_irq_chip *ic = irq_data_get_irq_chip_data(d);
+ u32 irq_bit = BIT(irqd_to_hwirq(d));
+ int this_cpu = smp_processor_id();
+
+ atomic_and(~irq_bit, &aic_vipi_mask[this_cpu]);
+
+ if (!atomic_read(&aic_vipi_mask[this_cpu]))
+ aic_ic_write(ic, AIC_IPI_MASK_SET, AIC_IPI_OTHER);
+}
+
+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));
+ int this_cpu = smp_processor_id();
+
+ /* Make sure the kernel's idea of logical CPU order is the same as AIC's */
+ WARN_ON(aic_ic_read(ic, AIC_WHOAMI) != this_cpu);
+
+ atomic_or(irq_bit, &aic_vipi_mask[this_cpu]);
+
+ aic_ic_write(ic, AIC_IPI_MASK_CLR, AIC_IPI_OTHER);
+}
+
+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;
+
+ for_each_cpu(cpu, mask) {
+ if (atomic_read(&aic_vipi_mask[cpu]) & irq_bit) {
+ atomic_or(irq_bit, &aic_vipi_flag[cpu]);
+ send |= AIC_IPI_SEND_CPU(cpu);
+ }
+ }
+
+ if (send) {
+ /*
+ * Ensure that stores to Normal memory are visible to the
+ * other CPUs before issuing the IPI.
+ */
+ wmb();
+ 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,
+};
+
+static void aic_handle_ipi(struct irq_desc *desc)
+{
+ struct irq_chip *chip = irq_desc_get_chip(desc);
+ int this_cpu = smp_processor_id();
+ int i;
+ unsigned long firing;
+
+ chained_irq_enter(chip, desc);
+ aic_ic_write(aic_irqc, AIC_IPI_ACK, AIC_IPI_OTHER);
+
+ firing = atomic_xchg(&aic_vipi_flag[this_cpu], 0);
+
+ for_each_set_bit(i, &firing, AIC_NR_SWIPI) {
+ generic_handle_irq(irq_find_mapping(aic_irqc->ipi_domain, i));
+ }
+
+ aic_ic_write(aic_irqc, AIC_IPI_MASK_CLR, AIC_IPI_OTHER);
+ chained_irq_exit(chip, desc);
+}
+
+static int aic_ipi_alloc(struct irq_domain *d, unsigned int virq,
+ unsigned int nr_irqs, void *args)
+{
+ 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 */
+}
+
+static const struct irq_domain_ops aic_ipi_domain_ops = {
+ .alloc = aic_ipi_alloc,
+ .free = aic_ipi_free,
+};
+
+static int aic_init_smp(struct aic_irq_chip *irqc, struct device_node *node)
+{
+ struct irq_fwspec ipi_fwspec = {
+ .fwnode = irqc->hw_domain->fwnode,
+ .param_count = 3,
+ .param = {
+ [0] = AIC_IPI,
+ [1] = 0,
+ [2] = 0,
+ },
+ };
+ int base_ipi, mux_irq;
+
+ mux_irq = irq_create_fwspec_mapping(&ipi_fwspec);
+ if (WARN_ON(mux_irq <= 0))
+ return -ENODEV;
+
+ irqc->ipi_domain =
+ irq_domain_create_linear(irqc->hw_domain->fwnode, AIC_NR_SWIPI,
+ &aic_ipi_domain_ops, irqc);
+ if (WARN_ON(!irqc->ipi_domain))
+ return -ENODEV;
+
+ irqc->ipi_domain->flags |= IRQ_DOMAIN_FLAG_IPI_SINGLE;
+ irq_domain_update_bus_token(irqc->ipi_domain, DOMAIN_BUS_IPI);
+
+ base_ipi = __irq_domain_alloc_irqs(irqc->ipi_domain, -1, AIC_NR_SWIPI,
+ NUMA_NO_NODE, NULL, false, NULL);
+
+ if (WARN_ON(!base_ipi)) {
+ irq_domain_remove(irqc->ipi_domain);
+ return -ENODEV;
+ }
+
+ set_smp_ipi_range(base_ipi, AIC_NR_SWIPI);
+
+ irq_set_chained_handler_and_data(mux_irq, aic_handle_ipi, NULL);
+
+ return 0;
+}
+
static int __init aic_of_ic_init(struct device_node *node,
struct device_node *parent)
{
@@ -298,6 +476,13 @@ static int __init aic_of_ic_init(struct device_node *node,

irq_domain_update_bus_token(irqc->hw_domain, DOMAIN_BUS_WIRED);

+ if (aic_init_smp(irqc, node)) {
+ irq_domain_remove(irqc->hw_domain);
+ iounmap(irqc->base);
+ kfree(irqc);
+ return -ENODEV;
+ }
+
set_handle_irq(aic_handle_irq_or_fiq);

for (i = 0; i < BITS_TO_LONGS(irqc->nr_hw); i++)
@@ -307,8 +492,8 @@ static int __init aic_of_ic_init(struct device_node *node,
for (i = 0; i < irqc->nr_hw; i++)
aic_ic_write(irqc, AIC_TARGET_CPU + i * 4, 1);

- pr_info("AIC: initialized with %d IRQs, %d FIQs, %d IPIs\n",
- irqc->nr_hw, AIC_NR_FIQ, AIC_NR_IPI);
+ pr_info("AIC: initialized with %d IRQs, %d FIQs, %d IPIs, %d vIPIs\n",
+ irqc->nr_hw, AIC_NR_FIQ, AIC_NR_IPI, AIC_NR_SWIPI);

return 0;
}
--
2.30.0
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