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Message-Id: <20221126173453.306088-4-apatel@ventanamicro.com> Date: Sat, 26 Nov 2022 23:04:49 +0530 From: Anup Patel <apatel@...tanamicro.com> To: Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, Thomas Gleixner <tglx@...utronix.de>, Marc Zyngier <maz@...nel.org>, Daniel Lezcano <daniel.lezcano@...aro.org> Cc: Atish Patra <atishp@...shpatra.org>, Alistair Francis <Alistair.Francis@....com>, Anup Patel <anup@...infault.org>, linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, Anup Patel <apatel@...tanamicro.com> Subject: [PATCH v12 3/7] genirq: Add mechanism to multiplex a single HW IPI All RISC-V platforms have a single HW IPI provided by the INTC local interrupt controller. The HW method to trigger INTC IPI can be through external irqchip (e.g. RISC-V AIA), through platform specific device (e.g. SiFive CLINT timer), or through firmware (e.g. SBI IPI call). To support multiple IPIs on RISC-V, we add a generic IPI multiplexing mechanism which help us create multiple virtual IPIs using a single HW IPI. This generic IPI multiplexing is inspired from the Apple AIC irqchip driver and it is shared by various RISC-V irqchip drivers. Signed-off-by: Anup Patel <apatel@...tanamicro.com> --- include/linux/irq.h | 4 + kernel/irq/Kconfig | 5 ++ kernel/irq/Makefile | 1 + kernel/irq/ipi-mux.c | 210 +++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 220 insertions(+) create mode 100644 kernel/irq/ipi-mux.c diff --git a/include/linux/irq.h b/include/linux/irq.h index c3eb89606c2b..6024e1ee1257 100644 --- a/include/linux/irq.h +++ b/include/linux/irq.h @@ -1266,6 +1266,10 @@ 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)(const struct cpumask *)); + #ifdef CONFIG_GENERIC_IRQ_MULTI_HANDLER /* * Registers a generic IRQ handling function as the top-level IRQ handler in diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig index db3d174c53d4..df17dbc54b02 100644 --- a/kernel/irq/Kconfig +++ b/kernel/irq/Kconfig @@ -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 interrupt support config GENERIC_MSI_IRQ bool diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile index b4f53717d143..f19d3080bf11 100644 --- a/kernel/irq/Makefile +++ b/kernel/irq/Makefile @@ -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 diff --git a/kernel/irq/ipi-mux.c b/kernel/irq/ipi-mux.c new file mode 100644 index 000000000000..366d8cd5320b --- /dev/null +++ b/kernel/irq/ipi-mux.c @@ -0,0 +1,210 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Multiplex several virtual IPIs over a single HW IPI. + * + * Copyright The Asahi Linux Contributors + * Copyright (c) 2022 Ventana Micro Systems Inc. + */ + +#define pr_fmt(fmt) "ipi-mux: " fmt +#include <linux/cpu.h> +#include <linux/init.h> +#include <linux/irq.h> +#include <linux/irqchip.h> +#include <linux/irqchip/chained_irq.h> +#include <linux/irqdomain.h> +#include <linux/jump_label.h> +#include <linux/percpu.h> +#include <linux/smp.h> + +struct ipi_mux_cpu { + atomic_t enable; + atomic_t bits; + struct cpumask send_mask; +}; + +static struct ipi_mux_cpu __percpu *ipi_mux_pcpu; +static struct irq_domain *ipi_mux_domain; +static void (*ipi_mux_send)(const struct cpumask *mask); + +static void ipi_mux_mask(struct irq_data *d) +{ + struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu); + + atomic_andnot(BIT(irqd_to_hwirq(d)), &icpu->enable); +} + +static void ipi_mux_unmask(struct irq_data *d) +{ + u32 ibit = BIT(irqd_to_hwirq(d)); + struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu); + + atomic_or(ibit, &icpu->enable); + + /* + * The atomic_or() above must complete before the atomic_read() + * below to avoid racing ipi_mux_send_mask(). + */ + smp_mb__after_atomic(); + + /* If a pending IPI was unmasked, raise a parent IPI immediately. */ + if (atomic_read(&icpu->bits) & ibit) + ipi_mux_send(cpumask_of(smp_processor_id())); +} + +static void ipi_mux_send_mask(struct irq_data *d, const struct cpumask *mask) +{ + u32 ibit = BIT(irqd_to_hwirq(d)); + struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu); + struct cpumask *send_mask = &icpu->send_mask; + unsigned long flags; + int cpu; + + /* + * We use send_mask as a per-CPU variable so disable local + * interrupts to avoid being preempted. + */ + local_irq_save(flags); + + cpumask_clear(send_mask); + + for_each_cpu(cpu, mask) { + icpu = per_cpu_ptr(ipi_mux_pcpu, cpu); + atomic_or(ibit, &icpu->bits); + + /* + * The atomic_or() above must complete before + * the atomic_read() below to avoid racing with + * ipi_mux_unmask(). + */ + smp_mb__after_atomic(); + + if (atomic_read(&icpu->enable) & ibit) + cpumask_set_cpu(cpu, send_mask); + } + + /* Trigger the parent IPI */ + ipi_mux_send(send_mask); + + local_irq_restore(flags); +} + +static const struct irq_chip ipi_mux_chip = { + .name = "IPI Mux", + .irq_mask = ipi_mux_mask, + .irq_unmask = ipi_mux_unmask, + .ipi_send_mask = ipi_mux_send_mask, +}; + +static int ipi_mux_domain_alloc(struct irq_domain *d, unsigned int virq, + unsigned int nr_irqs, void *arg) +{ + int i; + + for (i = 0; i < nr_irqs; i++) { + irq_set_percpu_devid(virq + i); + irq_domain_set_info(d, virq + i, i, + &ipi_mux_chip, d->host_data, + handle_percpu_devid_irq, NULL, NULL); + } + + return 0; +} + +static const struct irq_domain_ops ipi_mux_domain_ops = { + .alloc = ipi_mux_domain_alloc, + .free = irq_domain_free_irqs_top, +}; + +/** + * ipi_mux_process - Process multiplexed virtual IPIs + */ +void ipi_mux_process(void) +{ + struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu); + irq_hw_number_t hwirq; + unsigned long ipis; + unsigned int en; + + /* + * Reading enable mask does not need to be ordered as long as + * this function called from interrupt handler because only + * the CPU itself can change it's own enable mask. + */ + en = atomic_read(&icpu->enable); + + /* + * Clear the IPIs we are about to handle. This pairs with the + * atomic_fetch_or_release() in ipi_mux_send_mask(). + */ + ipis = atomic_fetch_andnot(en, &icpu->bits) & en; + + for_each_set_bit(hwirq, &ipis, BITS_PER_LONG) + generic_handle_domain_irq(ipi_mux_domain, hwirq); +} + +/** + * ipi_mux_create - Create virtual IPIs multiplexed on top of a single + * parent IPI. + * @nr_ipi: number of virtual IPIs to create. This should + * be <= BITS_PER_TYPE(int) + * @mux_send: callback to trigger parent IPI + * + * Returns first virq of the newly created virtual IPIs upon success + * or <=0 upon failure + */ +int ipi_mux_create(unsigned int nr_ipi, + void (*mux_send)(const struct cpumask *)) +{ + struct fwnode_handle *fwnode; + struct irq_domain *domain; + int rc; + + if (ipi_mux_domain) + return -EEXIST; + + if (BITS_PER_TYPE(int) < nr_ipi || !mux_send) + return -EINVAL; + + ipi_mux_pcpu = alloc_percpu(typeof(*ipi_mux_pcpu)); + if (!ipi_mux_pcpu) + return -ENOMEM; + + fwnode = irq_domain_alloc_named_fwnode("IPI-Mux"); + if (!fwnode) { + pr_err("unable to create IPI Mux fwnode\n"); + rc = -ENOMEM; + goto fail_free_cpu; + } + + domain = irq_domain_create_simple(fwnode, nr_ipi, 0, + &ipi_mux_domain_ops, NULL); + if (!domain) { + pr_err("unable to add IPI Mux domain\n"); + rc = -ENOMEM; + goto fail_free_fwnode; + } + + domain->flags |= IRQ_DOMAIN_FLAG_IPI_SINGLE; + irq_domain_update_bus_token(domain, DOMAIN_BUS_IPI); + + rc = __irq_domain_alloc_irqs(domain, -1, nr_ipi, + NUMA_NO_NODE, NULL, false, NULL); + if (rc <= 0) { + pr_err("unable to alloc IRQs from IPI Mux domain\n"); + goto fail_free_domain; + } + + ipi_mux_domain = domain; + ipi_mux_send = mux_send; + + return rc; + +fail_free_domain: + irq_domain_remove(domain); +fail_free_fwnode: + irq_domain_free_fwnode(fwnode); +fail_free_cpu: + free_percpu(ipi_mux_pcpu); + return rc; +} -- 2.34.1
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