From 835a486cd9f55790dee9f6b67ce0057d49f15da5 Mon Sep 17 00:00:00 2001 From: Anup Patel Date: Tue, 3 Jan 2023 19:42:15 +0530 Subject: [PATCH 1/3] 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, add a generic IPI multiplexing mechanism which help us create multiple virtual IPIs using a single HW IPI. This generic IPI multiplexing is inspired by the Apple AIC irqchip driver and it is shared by various RISC-V irqchip drivers. Signed-off-by: Anup Patel Reviewed-by: Hector Martin Tested-by: Hector Martin Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20230103141221.772261-4-apatel@ventanamicro.com --- include/linux/irq.h | 3 + kernel/irq/Kconfig | 5 ++ kernel/irq/Makefile | 1 + kernel/irq/ipi-mux.c | 207 +++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 216 insertions(+) create mode 100644 kernel/irq/ipi-mux.c diff --git a/include/linux/irq.h b/include/linux/irq.h index c3eb89606c2b1..b1b28affb32a7 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 b64c44ae4c250..2531f3496ab6d 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 hierarchical interrupt domain support config GENERIC_MSI_IRQ bool diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile index b4f53717d1434..f19d3080bf11a 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 0000000000000..3a403c3a785d1 --- /dev/null +++ b/kernel/irq/ipi-mux.c @@ -0,0 +1,207 @@ +// 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 +#include +#include +#include +#include +#include +#include +#include +#include + +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) +{ + struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu); + u32 ibit = BIT(irqd_to_hwirq(d)); + + 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) +{ + struct ipi_mux_cpu *icpu = this_cpu_ptr(ipi_mux_pcpu); + u32 ibit = BIT(irqd_to_hwirq(d)); + unsigned long pending; + int cpu; + + for_each_cpu(cpu, mask) { + icpu = per_cpu_ptr(ipi_mux_pcpu, cpu); + + /* + * This sequence is the mirror of the one in ipi_mux_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 ipi_mux_process(). + */ + 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 is 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; +} From c19f897194288ec286bb52001b9ee9551876a614 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Tue, 3 Jan 2023 19:42:21 +0530 Subject: [PATCH 2/3] irqchip/apple-aic: Move over to core ipi-mux Now that the complexity of the AIC IPI mux has been copied into the core code for the benefit of the riscv architecture, shrink the AIC driver by the same amount by using that infrastructure. Signed-off-by: Marc Zyngier Signed-off-by: Anup Patel Acked-by: Hector Martin Link: https://lore.kernel.org/r/20230103141221.772261-10-apatel@ventanamicro.com --- drivers/irqchip/Kconfig | 1 + drivers/irqchip/irq-apple-aic.c | 161 ++------------------------------ 2 files changed, 9 insertions(+), 153 deletions(-) diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig index caa952c40ff92..cbf504794e7c1 100644 --- a/drivers/irqchip/Kconfig +++ b/drivers/irqchip/Kconfig @@ -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. diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c index ae3437f03e6c2..eabb3b92965b2 100644 --- a/drivers/irqchip/irq-apple-aic.c +++ b/drivers/irqchip/irq-apple-aic.c @@ -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]; @@ -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); @@ -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. @@ -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 @@ -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; } From 3d812a0f27baa2d094f2c18298d48b012878dc0b Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 6 Feb 2023 17:21:15 +0000 Subject: [PATCH 3/3] genirq/ipi-mux: Use irq_domain_alloc_irqs() Using __irq_domain_alloc_irqs() is an unnecessary complexity. Use irq_domain_alloc_irqs(), which is simpler and makes the code more readable. Reported-by: Stephen Rothwell Signed-off-by: Marc Zyngier --- kernel/irq/ipi-mux.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/irq/ipi-mux.c b/kernel/irq/ipi-mux.c index 3a403c3a785d1..fa4fc18c61316 100644 --- a/kernel/irq/ipi-mux.c +++ b/kernel/irq/ipi-mux.c @@ -185,8 +185,7 @@ int ipi_mux_create(unsigned int nr_ipi, void (*mux_send)(unsigned int cpu)) 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); + rc = irq_domain_alloc_irqs(domain, nr_ipi, NUMA_NO_NODE, NULL); if (rc <= 0) { pr_err("unable to alloc IRQs from IPI Mux domain\n"); goto fail_free_domain;