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Message-ID: <cd4a5513197b73e3b8d335f09117bb8d@kernel.org>
Date: Sat, 30 May 2020 13:01:38 +0100
From: Marc Zyngier <maz@...nel.org>
To: Anup Patel <anup.patel@....com>
Cc: Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Albert Ou <aou@...s.berkeley.edu>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>,
Jason Cooper <jason@...edaemon.net>,
Atish Patra <atish.patra@....com>,
Alistair Francis <Alistair.Francis@....com>,
Anup Patel <anup@...infault.org>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
Palmer Dabbelt <palmerdabbelt@...gle.com>
Subject: Re: [PATCH v6 3/6] irqchip: RISC-V per-HART local interrupt
controller driver
On 2020-05-30 11:07, 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.
Please don't use "This patch...". Say something like:
"Add a driver driver for this component, which eventually replaces
the RISC-V architecture code, allowing for a better split between
arch code and drivers."
> It is a major re-write over perviously submitted version.
> (Refer, https://www.spinics.net/lists/devicetree/msg241230.html)
I'm not sure that's very useful. Again, this is better placed in the
cover letter, and can be retrived via the Link: tags.
> The driver is compliant with RISC-V Hart-Level Interrupt Controller
> DT bindings located at:
> Documentation/devicetree/bindings/interrupt-controller/riscv,cpu-intc.txt
>
> Co-developed-by: Palmer Dabbelt <palmer@...belt.com>
> Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
> Signed-off-by: Anup Patel <anup.patel@....com>
> Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.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 | 148 ++++++++++++++++++++++++++++++
> drivers/irqchip/irq-sifive-plic.c | 30 ++++--
> include/linux/cpuhotplug.h | 1 +
> 9 files changed, 191 insertions(+), 40 deletions(-)
> create mode 100644 drivers/irqchip/irq-riscv-intc.c
>
> 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..84e7bda3a090
> --- /dev/null
> +++ b/drivers/irqchip/irq-riscv-intc.c
> @@ -0,0 +1,148 @@
> +// 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/irqdomain.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/smp.h>
> +
> +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, 1UL << d->hwirq);
As I mentionned earlier, BIT(d->hwirq) is the way to write this.
> +}
> +
> +static void riscv_intc_irq_unmask(struct irq_data *d)
> +{
> + csr_set(CSR_IE, 1UL << 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);
> +
> + return 0;
> +}
> +
> +static const struct irq_domain_ops riscv_intc_domain_ops = {
> + .map = riscv_intc_domain_map,
> + .xlate = irq_domain_xlate_onecell,
> +};
> +
> +static int __init riscv_intc_init(struct device_node *node,
> + struct device_node *parent)
> +{
> + int rc, hartid;
> +
> + hartid = riscv_of_parent_hartid(node);
> + if (hartid < 0) {
> + pr_warn("unable to fine hart id for %pOF\n", node);
> + return 0;
> + }
> +
> + /*
> + * 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 to do INTC initialization
> + * for the INTC DT node belonging to boot CPU (or boot HART).
> + */
> + if (riscv_hartid_to_cpuid(hartid) != smp_processor_id())
> + return 0;
> +
> + intc_domain = irq_domain_add_linear(node, BITS_PER_LONG,
> + &riscv_intc_domain_ops, NULL);
> + if (!intc_domain) {
> + rc = -ENXIO;
> + pr_err("unable to add IRQ domain\n");
> + return rc;
Also written as "return -ENXIO".
> + }
> +
> + rc = set_handle_irq(&riscv_intc_irq);
> + if (rc) {
> + pr_err("failed to set irq handler\n");
> + return rc;
> + }
> +
> + cpuhp_setup_state(CPUHP_AP_IRQ_RISCV_STARTING,
> + "irqchip/riscv/intc:starting",
> + riscv_intc_cpu_starting,
> + riscv_intc_cpu_dying);
> +
> + pr_info("%d local interrupts mapped\n", BITS_PER_LONG);
> +
> + return 0;
> +}
> +
> +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..cda2e246aee3 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -9,6 +9,7 @@
> #include <linux/io.h>
> #include <linux/irq.h>
> #include <linux/irqchip.h>
> +#include <linux/irqchip/chained_irq.h>
> #include <linux/irqdomain.h>
> #include <linux/module.h>
> #include <linux/of.h>
> @@ -76,6 +77,7 @@ struct plic_handler {
> void __iomem *enable_base;
> struct plic_priv *priv;
> };
> +static int plic_parent_irq;
> static bool plic_cpuhp_setup_done;
> static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
>
> @@ -219,15 +221,17 @@ 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);
> +
> while ((hwirq = readl(claim))) {
> int irq = irq_find_mapping(handler->priv->irqdomain, hwirq);
>
> @@ -237,7 +241,8 @@ 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 +255,8 @@ static int plic_dying_cpu(unsigned int cpu)
> {
> struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
>
> - csr_clear(CSR_IE, IE_EIE);
> + if (plic_parent_irq)
> + disable_percpu_irq(plic_parent_irq);
Given what is below, is that something that can happen if
plic_parent_irq is 0?
> plic_set_threshold(handler, PLIC_DISABLE_THRESHOLD);
Why do you need to both disable the interrupt *and* change the priority
threshold? It seems to be that one of them should be enough, but my
kno9wledge of the PLIC is limited. In any case, this would deserve a
comment.
>
> return 0;
> @@ -260,7 +266,11 @@ static int plic_starting_cpu(unsigned int cpu)
> {
> struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
>
> - csr_set(CSR_IE, IE_EIE);
> + if (plic_parent_irq)
> + enable_percpu_irq(plic_parent_irq,
> + irq_get_trigger_type(plic_parent_irq));
> + else
> + pr_warn("cpu%d: parent irq not available\n");
What does it mean to carry on if the interrupt cannot be signaled?
Shouldn't you error out instead, and leave the CPU dead?
> plic_set_threshold(handler, PLIC_ENABLE_THRESHOLD);
>
> return 0;
> @@ -273,6 +283,7 @@ 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;
Unused variable?
>
> priv = kzalloc(sizeof(*priv), GFP_KERNEL);
> if (!priv)
> @@ -328,6 +339,14 @@ static int __init plic_init(struct device_node
> *node,
> continue;
> }
>
> + /* Find parent domain and register chained handler */
> + if (!plic_parent_irq && irq_find_host(parent.np)) {
> + plic_parent_irq = irq_of_parse_and_map(node, i);
> + if (plic_parent_irq)
> + irq_set_chained_handler(plic_parent_irq,
> + plic_handle_irq);
> + }
> +
> /*
> * When running in M-mode we need to ignore the S-mode handler.
> * Here we assume it always comes later, but that might be a
> @@ -368,7 +387,6 @@ 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,
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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