[v14,3/8] genirq: Add mechanism to multiplex a single HW IPI

Message ID	20221201130135.1115380-4-apatel@ventanamicro.com (mailing list archive)
State	Superseded
Headers	show Return-Path: <linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org> From: Anup Patel <apatel@ventanamicro.com> To: Palmer Dabbelt <palmer@dabbelt.com>, Paul Walmsley <paul.walmsley@sifive.com>, Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <maz@kernel.org>, Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Atish Patra <atishp@atishpatra.org>, Alistair Francis <Alistair.Francis@wdc.com>, Anup Patel <anup@brainfault.org>, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Anup Patel <apatel@ventanamicro.com> Subject: [PATCH v14 3/8] genirq: Add mechanism to multiplex a single HW IPI Date: Thu, 1 Dec 2022 18:31:30 +0530 Message-Id: <20221201130135.1115380-4-apatel@ventanamicro.com> In-Reply-To: <20221201130135.1115380-1-apatel@ventanamicro.com> References: <20221201130135.1115380-1-apatel@ventanamicro.com> MIME-Version: 1.0 Precedence: list Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" <linux-riscv-bounces@lists.infradead.org> Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org
Series	RISC-V IPI Improvements \| expand [v14,0/8] RISC-V IPI Improvements [v14,1/8] RISC-V: Clear SIP bit only when using SBI IPI operations [v14,2/8] irqchip/riscv-intc: Allow drivers to directly discover INTC hwnode [v14,3/8] genirq: Add mechanism to multiplex a single HW IPI [v14,4/8] RISC-V: Treat IPIs as normal Linux IRQs [v14,5/8] RISC-V: Allow marking IPIs as suitable for remote FENCEs [v14,6/8] RISC-V: Use IPIs for remote TLB flush when possible [v14,7/8] RISC-V: Use IPIs for remote icache flush when possible [v14,8/8] irqchip/riscv-intc: Add empty irq_eoi() for chained irq handlers

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diff --git a/include/linux/irq.h b/include/linux/irq.h index c3eb89606c2b..b1b28affb32a 100644 --- a/include/linux/irq.h +++ b/include/linux/irq.h @@ -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 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..1a6ba19b736c --- /dev/null +++ b/kernel/irq/ipi-mux.c @@ -0,0 +1,199 @@ +// 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; +}; + +static struct ipi_mux_cpu __percpu *ipi_mux_pcpu; +static struct irq_domain *ipi_mux_domain; +static void (*ipi_mux_send)(unsigned int cpu); + +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(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); + unsigned long pending; + int cpu; + + for_each_cpu(cpu, mask) { + icpu = per_cpu_ptr(ipi_mux_pcpu, cpu); + pending = atomic_fetch_or_release(ibit, &icpu->bits); + + /* + * The atomic_fetch_or_release() above must complete + * before the atomic_read() below to avoid racing with + * ipi_mux_unmask(). + */ + smp_mb__after_atomic(); + + /* + * 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() below, which is + * itself already ordered after the vIPI flag write. + */ + if (!(pending & ibit) && (atomic_read(&icpu->enable) & ibit)) + ipi_mux_send(cpu); + } +} + +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, NULL, + 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_TYPE(int)) + 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 for a particular CPU + * + * 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)(unsigned int cpu)) +{ + 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_linear(fwnode, nr_ipi, + &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; +}

[v14,3/8] genirq: Add mechanism to multiplex a single HW IPI

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