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Date: Sun, 31 May 2020 11:06:45 +0530
From: Anup Patel <anup@...infault.org>
To: Marc Zyngier <maz@...nel.org>
Cc: Anup Patel <anup.patel@....com>,
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>,
linux-riscv <linux-riscv@...ts.infradead.org>,
"linux-kernel@...r.kernel.org List" <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 Sat, May 30, 2020 at 5:31 PM Marc Zyngier <maz@...nel.org> wrote:
>
> 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."
Okay, will update.
>
> > 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.
Okay, will update.
>
> > 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.
Okay, will update here and below as well.
>
> > +}
> > +
> > +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".
Okay, will update.
>
> > + }
> > +
> > + 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?
For multiple PLIC instances, the plic_init() will be called once for each
PLIC instance. The "interrupts-extended" property of one of the PLIC DT
node must point to boot CPU INTC DT node for plic_parent_irq to be found.
The plic_parent_irq can be 0 only if none of PLIC DT nodes point to
boot CPU INTC DT node.
>
> > 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.
Okay, I will test and remove "disable the interrupt" part from plic_dying_cpu().
>
> >
> > 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?
The CPU is not dead if we cannot enable RISC-V INTC external
interrupt because the Timer and IPIs interrupts are always through
RISC-V INTC. The PLIC external interrupt not present for a CPU
only means that that CPU cannot receive peripherial interrupts.
On a sane RISC-V system, if PLIC is present then all CPUs should
be able to get RISC-V INTC external interrupt. Base on this rationale,
I have put a warning for plic_parent_irq == 0.
>
> > 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?
Okay, will update.
>
> >
> > 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...
Regards,
Anup
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