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Message-ID: <mhng-0403a86a-bda6-4e69-ad73-71fb06c49e40@palmerdabbelt-glaptop1>
Date: Thu, 28 May 2020 19:40:29 -0700 (PDT)
From: Palmer Dabbelt <palmer@...belt.com>
To: Anup Patel <Anup.Patel@....com>
CC: Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
daniel.lezcano@...aro.org, tglx@...utronix.de,
jason@...edaemon.net, Marc Zyngier <maz@...nel.org>,
Atish Patra <Atish.Patra@....com>,
Alistair Francis <Alistair.Francis@....com>,
anup@...infault.org, linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org, Anup Patel <Anup.Patel@....com>
Subject: Re: [PATCH v5 3/6] irqchip: RISC-V per-HART local interrupt controller driver
On Thu, 21 May 2020 06:32:58 PDT (-0700), Anup Patel wrote:
> The RISC-V per-HART local interrupt controller manages software
> interrupts, timer interrupts, external interrupts (which are routed
> via the platform level interrupt controller) and other per-HART
> local interrupts.
>
> This patch adds a driver for the RISC-V local interrupt controller.
> It is a major re-write over perviously submitted version.
> (Refer, https://www.spinics.net/lists/devicetree/msg241230.html)
>
> Few advantages of this new driver over previous one are:
> 1. All local interrupts are registered as per-CPU interrupts
> 2. The RISC-V timer driver can register timer interrupt handler
> using kernel irq subsystem without relying on arch/riscv to
> explicitly call it's interrupt handler
> 3. The KVM RISC-V can use this driver to implement interrupt
> handler for per-HART guest external interrupt defined by
> the RISC-V H-Extension
> 4. In future, we can develop drivers for devices with per-HART
> interrupts without changing arch code or this driver (example,
> CLINT timer driver for RISC-V M-mode kernel)
>
> The RISC-V INTC driver is compliant with RISC-V Hart-Level Interrupt
> Controller DT bindings located at:
> Documentation/devicetree/bindings/interrupt-controller/riscv,cpu-intc.txt
>
> Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
> Signed-off-by: Anup Patel <anup.patel@....com>
> ---
> arch/riscv/Kconfig | 1 +
> arch/riscv/include/asm/irq.h | 2 -
> arch/riscv/kernel/irq.c | 33 +-----
> arch/riscv/kernel/traps.c | 2 -
> drivers/irqchip/Kconfig | 13 ++
> drivers/irqchip/Makefile | 1 +
> drivers/irqchip/irq-riscv-intc.c | 158 +++++++++++++++++++++++++
> drivers/irqchip/irq-sifive-plic.c | 38 +++++-
> include/linux/cpuhotplug.h | 1 +
> include/linux/irqchip/irq-riscv-intc.h | 20 ++++
> 10 files changed, 229 insertions(+), 40 deletions(-)
> create mode 100644 drivers/irqchip/irq-riscv-intc.c
> create mode 100644 include/linux/irqchip/irq-riscv-intc.h
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 90a008e28f7e..822cb0e1a380 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -40,6 +40,7 @@ config RISCV
> select HAVE_PERF_REGS
> select HAVE_PERF_USER_STACK_DUMP
> select HAVE_SYSCALL_TRACEPOINTS
> + select HANDLE_DOMAIN_IRQ
> select IRQ_DOMAIN
> select SPARSE_IRQ
> select SYSCTL_EXCEPTION_TRACE
> diff --git a/arch/riscv/include/asm/irq.h b/arch/riscv/include/asm/irq.h
> index 0183e15ace66..a9e5f07a7e9c 100644
> --- a/arch/riscv/include/asm/irq.h
> +++ b/arch/riscv/include/asm/irq.h
> @@ -10,8 +10,6 @@
> #include <linux/interrupt.h>
> #include <linux/linkage.h>
>
> -#define NR_IRQS 0
> -
> void riscv_timer_interrupt(void);
>
> #include <asm-generic/irq.h>
> diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
> index bb0bfcd537e7..eb8777642ce6 100644
> --- a/arch/riscv/kernel/irq.c
> +++ b/arch/riscv/kernel/irq.c
> @@ -7,7 +7,6 @@
>
> #include <linux/interrupt.h>
> #include <linux/irqchip.h>
> -#include <linux/irqdomain.h>
> #include <linux/seq_file.h>
> #include <asm/smp.h>
>
> @@ -19,39 +18,13 @@ int arch_show_interrupts(struct seq_file *p, int prec)
>
> asmlinkage __visible void __irq_entry do_IRQ(struct pt_regs *regs)
> {
> - struct pt_regs *old_regs;
> -
> - switch (regs->cause & ~CAUSE_IRQ_FLAG) {
> - case RV_IRQ_TIMER:
> - old_regs = set_irq_regs(regs);
> - irq_enter();
> - riscv_timer_interrupt();
> - irq_exit();
> - set_irq_regs(old_regs);
> - break;
> -#ifdef CONFIG_SMP
> - case RV_IRQ_SOFT:
> - /*
> - * We only use software interrupts to pass IPIs, so if a non-SMP
> - * system gets one, then we don't know what to do.
> - */
> - handle_IPI(regs);
> - break;
> -#endif
> - case RV_IRQ_EXT:
> - old_regs = set_irq_regs(regs);
> - irq_enter();
> + if (handle_arch_irq)
> handle_arch_irq(regs);
> - irq_exit();
> - set_irq_regs(old_regs);
> - break;
> - default:
> - pr_alert("unexpected interrupt cause 0x%lx", regs->cause);
> - BUG();
> - }
> }
>
> void __init init_IRQ(void)
> {
> irqchip_init();
> + if (!handle_arch_irq)
> + panic("No interrupt controller found.");
> }
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index 7f58fa53033f..f48c76aadbf3 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -178,6 +178,4 @@ void trap_init(void)
> csr_write(CSR_SCRATCH, 0);
> /* Set the exception vector address */
> csr_write(CSR_TVEC, &handle_exception);
> - /* Enable interrupts */
> - csr_write(CSR_IE, IE_SIE);
> }
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index a85aada04a64..95d6137a8117 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -493,6 +493,19 @@ config TI_SCI_INTA_IRQCHIP
> If you wish to use interrupt aggregator irq resources managed by the
> TI System Controller, say Y here. Otherwise, say N.
>
> +config RISCV_INTC
> + bool "RISC-V Local Interrupt Controller"
> + depends on RISCV
> + default y
> + help
> + This enables support for the per-HART local interrupt controller
> + found in standard RISC-V systems. The per-HART local interrupt
> + controller handles timer interrupts, software interrupts, and
> + hardware interrupts. Without a per-HART local interrupt controller,
> + a RISC-V system will be unable to handle any interrupts.
> +
> + If you don't know what to do here, say Y.
> +
> config SIFIVE_PLIC
> bool "SiFive Platform-Level Interrupt Controller"
> depends on RISCV
> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> index 37bbe39bf909..b8319f045472 100644
> --- a/drivers/irqchip/Makefile
> +++ b/drivers/irqchip/Makefile
> @@ -98,6 +98,7 @@ obj-$(CONFIG_NDS32) += irq-ativic32.o
> obj-$(CONFIG_QCOM_PDC) += qcom-pdc.o
> obj-$(CONFIG_CSKY_MPINTC) += irq-csky-mpintc.o
> obj-$(CONFIG_CSKY_APB_INTC) += irq-csky-apb-intc.o
> +obj-$(CONFIG_RISCV_INTC) += irq-riscv-intc.o
> obj-$(CONFIG_SIFIVE_PLIC) += irq-sifive-plic.o
> obj-$(CONFIG_IMX_IRQSTEER) += irq-imx-irqsteer.o
> obj-$(CONFIG_IMX_INTMUX) += irq-imx-intmux.o
> diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
> new file mode 100644
> index 000000000000..2f364e6a87f9
> --- /dev/null
> +++ b/drivers/irqchip/irq-riscv-intc.c
> @@ -0,0 +1,158 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2012 Regents of the University of California
> + * Copyright (C) 2017-2018 SiFive
> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> + */
> +
> +#define pr_fmt(fmt) "riscv-intc: " fmt
> +#include <linux/atomic.h>
> +#include <linux/bits.h>
> +#include <linux/cpu.h>
> +#include <linux/irq.h>
> +#include <linux/irqchip.h>
> +#include <linux/irqchip/irq-riscv-intc.h>
> +#include <linux/irqdomain.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/smp.h>
> +
> +static struct device_node *intc_domain_node;
> +static struct irq_domain *intc_domain;
> +
> +static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
> +{
> + struct pt_regs *old_regs;
> + unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
> +
> + if (unlikely(cause >= BITS_PER_LONG))
> + panic("unexpected interrupt cause");
> +
> + switch (cause) {
> + case RV_IRQ_TIMER:
> + old_regs = set_irq_regs(regs);
> + irq_enter();
> + riscv_timer_interrupt();
> + irq_exit();
> + set_irq_regs(old_regs);
> + break;
> +#ifdef CONFIG_SMP
> + case RV_IRQ_SOFT:
> + /*
> + * We only use software interrupts to pass IPIs, so if a
> + * non-SMP system gets one, then we don't know what to do.
> + */
> + handle_IPI(regs);
> + break;
> +#endif
> + default:
> + handle_domain_irq(intc_domain, cause, regs);
> + break;
> + }
> +}
> +
> +/*
> + * On RISC-V systems local interrupts are masked or unmasked by writing
> + * the SIE (Supervisor Interrupt Enable) CSR. As CSRs can only be written
> + * on the local hart, these functions can only be called on the hart that
> + * corresponds to the IRQ chip.
> + */
> +
> +static void riscv_intc_irq_mask(struct irq_data *d)
> +{
> + csr_clear(CSR_IE, 1 << (long)d->hwirq);
> +}
> +
> +static void riscv_intc_irq_unmask(struct irq_data *d)
> +{
> + csr_set(CSR_IE, 1 << (long)d->hwirq);
> +}
> +
> +static int riscv_intc_cpu_starting(unsigned int cpu)
> +{
> + csr_write(CSR_IE, 1UL << RV_IRQ_SOFT);
> + csr_write(CSR_IP, 0);
> + return 0;
> +}
> +
> +static int riscv_intc_cpu_dying(unsigned int cpu)
> +{
> + csr_clear(CSR_IE, 1UL << RV_IRQ_SOFT);
> + return 0;
> +}
> +
> +static struct irq_chip riscv_intc_chip = {
> + .name = "RISC-V INTC",
> + .irq_mask = riscv_intc_irq_mask,
> + .irq_unmask = riscv_intc_irq_unmask,
> +};
> +
> +static int riscv_intc_domain_map(struct irq_domain *d, unsigned int irq,
> + irq_hw_number_t hwirq)
> +{
> + irq_set_percpu_devid(irq);
> + irq_domain_set_info(d, irq, hwirq, &riscv_intc_chip, d->host_data,
> + handle_percpu_devid_irq, NULL, NULL);
> + irq_set_status_flags(irq, IRQ_NOAUTOEN);
> +
> + return 0;
> +}
> +
> +static const struct irq_domain_ops riscv_intc_domain_ops = {
> + .map = riscv_intc_domain_map,
> + .xlate = irq_domain_xlate_onecell,
> +};
> +
> +/* Get the OF device node used by INTC irq domain */
> +struct device_node *riscv_of_intc_domain_node(void)
> +{
> + return intc_domain_node;
> +}
> +EXPORT_SYMBOL_GPL(riscv_of_intc_domain_node);
> +
> +static int __init riscv_intc_init(struct device_node *node,
> + struct device_node *parent)
> +{
> + int hartid;
> +
> + /*
> + * The DT will have one INTC DT node under each CPU (or HART)
> + * DT node so riscv_intc_init() function will be called once
> + * for each INTC DT node. We only need INTC initialization for
> + * the INTC DT node belonging to boot CPU (or boot HART).
> + */
> + hartid = riscv_of_parent_hartid(node);
> + if (hartid < 0)
> + return 0;
This should at least be a warning, as it's an invalid device tree.
> + if (riscv_hartid_to_cpuid(hartid) != smp_processor_id())
> + return 0;
There should be a comment about this one, as it only works becuase there's one
CPU up and running while interrupts are being enabled.
> +
> + intc_domain = irq_domain_add_linear(node, BITS_PER_LONG,
> + &riscv_intc_domain_ops, NULL);
> + if (!intc_domain)
> + goto error_add_linear;
> +
> + /*
> + * We save the DT node used for creating irq domain and provide
> + * it to other drivers using iscv_of_intc_domain_node() function.
Missing the "r" in iscv_of_intc_domain_node
> + */
> + intc_domain_node = of_node_get(node);
> +
> + set_handle_irq(&riscv_intc_irq);
So there's now this implicit assumption that every CPU node has a
riscv,cpu-intc. That's probably fine, as we don't have any other first-level
interrupt controllers, but at least whacking a warning if set_handle_irq()
fails seems prudent. It'd be best to actually check that assumption (maybe
before quitting above?) and actually installing the percpu OF nodes, but that
would take a performance hit so I'm not sure it's worth it.
> +
> + cpuhp_setup_state(CPUHP_AP_IRQ_RISCV_STARTING,
> + "irqchip/riscv/intc:starting",
> + riscv_intc_cpu_starting,
> + riscv_intc_cpu_dying);
> +
> + pr_info("%lu local interrupts mapped\n", (long)BITS_PER_LONG);
> +
> + return 0;
> +
> +error_add_linear:
> + pr_warn("unable to add IRQ domain\n");
> + return -ENXIO;
> +}
> +
> +IRQCHIP_DECLARE(riscv, "riscv,cpu-intc", riscv_intc_init);
> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> index 16d31d114c30..4f9b2877aa9d 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -9,6 +9,8 @@
> #include <linux/io.h>
> #include <linux/irq.h>
> #include <linux/irqchip.h>
> +#include <linux/irqchip/chained_irq.h>
> +#include <linux/irqchip/irq-riscv-intc.h>
> #include <linux/irqdomain.h>
> #include <linux/module.h>
> #include <linux/of.h>
> @@ -60,6 +62,7 @@
> #define PLIC_ENABLE_THRESHOLD 0
>
> struct plic_priv {
> + int parent_irq;
> struct cpumask lmask;
> struct irq_domain *irqdomain;
> void __iomem *regs;
> @@ -219,15 +222,17 @@ static const struct irq_domain_ops plic_irqdomain_ops = {
> * that source ID back to the same claim register. This automatically enables
> * and disables the interrupt, so there's nothing else to do.
> */
> -static void plic_handle_irq(struct pt_regs *regs)
> +static void plic_handle_irq(struct irq_desc *desc)
> {
> struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
> + struct irq_chip *chip = irq_desc_get_chip(desc);
> void __iomem *claim = handler->hart_base + CONTEXT_CLAIM;
> irq_hw_number_t hwirq;
>
> WARN_ON_ONCE(!handler->present);
>
> - csr_clear(CSR_IE, IE_EIE);
> + chained_irq_enter(chip, desc);
> +
Ya, it's pretty clear putting the local interrupt controller in irqchip is the
right way to go :)
> while ((hwirq = readl(claim))) {
> int irq = irq_find_mapping(handler->priv->irqdomain, hwirq);
>
> @@ -237,7 +242,8 @@ static void plic_handle_irq(struct pt_regs *regs)
> else
> generic_handle_irq(irq);
> }
> - csr_set(CSR_IE, IE_EIE);
> +
> + chained_irq_exit(chip, desc);
> }
>
> static void plic_set_threshold(struct plic_handler *handler, u32 threshold)
> @@ -250,7 +256,8 @@ static int plic_dying_cpu(unsigned int cpu)
> {
> struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
>
> - csr_clear(CSR_IE, IE_EIE);
> + if (handler->priv->parent_irq)
> + disable_percpu_irq(handler->priv->parent_irq);
> plic_set_threshold(handler, PLIC_DISABLE_THRESHOLD);
>
> return 0;
> @@ -259,8 +266,10 @@ static int plic_dying_cpu(unsigned int cpu)
> static int plic_starting_cpu(unsigned int cpu)
> {
> struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
> + int pirq = handler->priv->parent_irq;
>
> - csr_set(CSR_IE, IE_EIE);
> + if (pirq)
> + enable_percpu_irq(pirq, irq_get_trigger_type(pirq));
> plic_set_threshold(handler, PLIC_ENABLE_THRESHOLD);
>
> return 0;
> @@ -273,6 +282,7 @@ static int __init plic_init(struct device_node *node,
> u32 nr_irqs;
> struct plic_priv *priv;
> struct plic_handler *handler;
> + struct of_phandle_args intc_args;
>
> priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> if (!priv)
> @@ -354,6 +364,23 @@ static int __init plic_init(struct device_node *node,
> nr_handlers++;
> }
>
> + /*
> + * We can have multiple PLIC instances so setup chained handler
> + * for all PLIC instances.
> + */
> + intc_args.np = riscv_of_intc_domain_node();
> + intc_args.args_count = 1;
> + intc_args.args[0] = RV_IRQ_EXT;
You could just use the value from the device tree rather than deciding on the
value a-priori. It's a bit pedantic to worry about that now, as the PLIC
assumes that there's a RISC-V system and its parent is an cpu-intc, but it
always seems ugly that the PLIC driver is so RISC-V specific.
> + priv->parent_irq = irq_create_of_mapping(&intc_args);
> + if (priv->parent_irq)
> + irq_set_chained_handler(priv->parent_irq,
> + plic_handle_irq);
> + else {
> + pr_err("%pOFP: intc mapping failed\n", node);
> + error = -ENODEV;
> + goto out_iounmap;
> + }
> +
> /*
> * We can have multiple PLIC instances so setup cpuhp state only
> * when context handler for current/boot CPU is present.
> @@ -368,7 +395,6 @@ static int __init plic_init(struct device_node *node,
>
> pr_info("%pOFP: mapped %d interrupts with %d handlers for"
> " %d contexts.\n", node, nr_irqs, nr_handlers, nr_contexts);
> - set_handle_irq(plic_handle_irq);
> return 0;
>
> out_iounmap:
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 77d70b633531..57b1f8f777d9 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -102,6 +102,7 @@ enum cpuhp_state {
> CPUHP_AP_IRQ_ARMADA_XP_STARTING,
> CPUHP_AP_IRQ_BCM2836_STARTING,
> CPUHP_AP_IRQ_MIPS_GIC_STARTING,
> + CPUHP_AP_IRQ_RISCV_STARTING,
> CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
> CPUHP_AP_ARM_MVEBU_COHERENCY,
> CPUHP_AP_MICROCODE_LOADER,
> diff --git a/include/linux/irqchip/irq-riscv-intc.h b/include/linux/irqchip/irq-riscv-intc.h
> new file mode 100644
> index 000000000000..b11d38353099
> --- /dev/null
> +++ b/include/linux/irqchip/irq-riscv-intc.h
> @@ -0,0 +1,20 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> + */
> +
> +#ifndef __INCLUDE_LINUX_IRQCHIP_IRQ_RISCV_INTC_H
> +#define __INCLUDE_LINUX_IRQCHIP_IRQ_RISCV_INTC_H
> +
> +struct device_node;
> +
> +#ifdef CONFIG_RISCV_INTC
> +struct device_node *riscv_of_intc_domain_node(void);
> +#else
> +static inline struct device_node *riscv_of_intc_domain_node(void)
> +{
> + return NULL;
> +}
> +#endif
> +
> +#endif
These issues are all pretty minor, so I'm OK with this getting merged as-is. I
fixed up some minor stuff and have it on my intc branch as 2bd957e2b0b6
("irqchip: RISC-V per-HART local interrupt controller driver"), but if the
irqchip folks want to take the patches then I'm not opposed to either version
getting merged.
Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
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