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SubjectRe: [PATCH 7/8] irqchip: add a SiFive PLIC driver
Date
On 8/4/18 1:23 AM, Christoph Hellwig wrote:
> Adds a driver for the SiFive implementation of the RISC-V Platform Level
> Interrupt Controller (PLIC). The PLIC connects global interrupt sources
> to the local interrupt controller on each hart.
>
> This driver is based on the driver in the RISC-V tree from Palmer Dabbelt,
> but has been almost entirely rewritten since, and includes many fixes
> from Atish Patra.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Thomas Gleixner <tglx@linutronix.de>
> ---
> arch/riscv/configs/defconfig | 1 +
> drivers/irqchip/Kconfig | 12 ++
> drivers/irqchip/Makefile | 1 +
> drivers/irqchip/irq-sifive-plic.c | 259 ++++++++++++++++++++++++++++++
> 4 files changed, 273 insertions(+)
> create mode 100644 drivers/irqchip/irq-sifive-plic.c
>
> diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
> index 07326466871b..36473d7dbaac 100644
> --- a/arch/riscv/configs/defconfig
> +++ b/arch/riscv/configs/defconfig
> @@ -76,3 +76,4 @@ CONFIG_ROOT_NFS=y
> CONFIG_CRYPTO_USER_API_HASH=y
> CONFIG_MODULES=y
> CONFIG_MODULE_UNLOAD=y
> +CONFIG_SIFIVE_PLIC=y
> diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
> index e9233db16e03..df345b878ac2 100644
> --- a/drivers/irqchip/Kconfig
> +++ b/drivers/irqchip/Kconfig
> @@ -372,3 +372,15 @@ config QCOM_PDC
> IRQs for Qualcomm Technologies Inc (QTI) mobile chips.
>
> endmenu
> +
> +config SIFIVE_PLIC
> + bool "SiFive Platform-Level Interrupt Controller"
> + depends on RISCV
> + help
> + This enables support for the PLIC chip found in SiFive (and
> + potentially other) RISC-V systems. The PLIC controls devices
> + interrupts and connects them to each core's local interrupt
> + controller. Aside from timer and software interrupts, all other
> + interrupt sources are subordinate to the PLIC.
> +
> + If you don't know what to do here, say Y.
> diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
> index 15f268f646bf..fbd1ec8070ef 100644
> --- a/drivers/irqchip/Makefile
> +++ b/drivers/irqchip/Makefile
> @@ -87,3 +87,4 @@ obj-$(CONFIG_MESON_IRQ_GPIO) += irq-meson-gpio.o
> obj-$(CONFIG_GOLDFISH_PIC) += irq-goldfish-pic.o
> obj-$(CONFIG_NDS32) += irq-ativic32.o
> obj-$(CONFIG_QCOM_PDC) += qcom-pdc.o
> +obj-$(CONFIG_SIFIVE_PLIC) += irq-sifive-plic.o
> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> new file mode 100644
> index 000000000000..faacf428e250
> --- /dev/null
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -0,0 +1,259 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2017 SiFive
> + * Copyright (C) 2018 Christoph Hellwig
> + */
> +#define pr_fmt(fmt) "plic: " fmt
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/irq.h>
> +#include <linux/irqchip.h>
> +#include <linux/irqdomain.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/platform_device.h>
> +#include <linux/spinlock.h>
> +
> +/*
> + * This driver implements a version of the RISC-V PLIC with the actual layout
> + * specified in chapter 8 of the SiFive U5 Coreplex Series Manual:
> + *
> + * https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf
> + *
> + * The largest number supported by devices marked as 'riscv,plic0', is 1024, of
> + * which device 0 is defined as non-existent by the RISC-V Privileged Spec.
> + */
> +
> +#define MAX_DEVICES 1024
> +#define MAX_CONTEXTS 15872
> +
> +/*
> + * Each interrupt source has a priority register associated with it.
> + * We always hardwire it to one in Linux.
> + */
> +#define PRIORITY_BASE 0
> +#define PRIORITY_PER_ID 4
> +
> +/*
> + * Each hart context has a vector of interrupt enable bits associated with it.
> + * There's one bit for each interrupt source.
> + */
> +#define ENABLE_BASE 0x2000
> +#define ENABLE_PER_HART 0x80
> +
> +/*
> + * Each hart context has a set of control registers associated with it. Right
> + * now there's only two: a source priority threshold over which the hart will
> + * take an interrupt, and a register to claim interrupts.
> + */
> +#define CONTEXT_BASE 0x200000
> +#define CONTEXT_PER_HART 0x1000
> +#define CONTEXT_THRESHOLD 0x00
> +#define CONTEXT_CLAIM 0x04
> +
> +static void __iomem *plic_regs;
> +
> +struct plic_handler {
> + bool present;
> + int ctxid;
> +};
> +static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
> +
> +static inline void __iomem *plic_hart_offset(int ctxid)
> +{
> + return plic_regs + CONTEXT_BASE + ctxid * CONTEXT_PER_HART;
> +}
> +
> +static inline u32 __iomem *plic_enable_base(int ctxid)
> +{
> + return plic_regs + ENABLE_BASE + ctxid * ENABLE_PER_HART;
> +}
> +
> +/*
> + * Protect mask operations on the registers given that we can't assume that
> + * atomic memory operations work on them.
> + */
> +static DEFINE_RAW_SPINLOCK(plic_toggle_lock);
> +
> +static inline void plic_toggle(int ctxid, int hwirq, int enable)
> +{
> + u32 __iomem *reg = plic_enable_base(ctxid) + (hwirq / 32);
> + u32 hwirq_mask = 1 << (hwirq % 32);
> +
> + raw_spin_lock(&plic_toggle_lock);
> + if (enable)
> + writel(readl(reg) | hwirq_mask, reg);
> + else
> + writel(readl(reg) & ~hwirq_mask, reg);
> + raw_spin_unlock(&plic_toggle_lock);
> +}
> +
> +static inline void plic_irq_toggle(struct irq_data *d, int enable)
> +{
> + int cpu;
> +
> + writel(enable, plic_regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID);
> + for_each_cpu(cpu, irq_data_get_affinity_mask(d)) {
> + struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
> +
> + if (handler->present)
> + plic_toggle(handler->ctxid, d->hwirq, enable);
> + }
> +}
> +
> +static void plic_irq_enable(struct irq_data *d)
> +{
> + plic_irq_toggle(d, 1);
> +}
> +
> +static void plic_irq_disable(struct irq_data *d)
> +{
> + plic_irq_toggle(d, 0);
> +}
> +
> +static struct irq_chip plic_chip = {
> + .name = "SiFive PLIC",
> + /*
> + * There is no need to mask/unmask PLIC interrupts. They are "masked"
> + * by reading claim and "unmasked" when writing it back.
> + */
> + .irq_enable = plic_irq_enable,
> + .irq_disable = plic_irq_disable,
> +};
> +
> +static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
> + irq_hw_number_t hwirq)
> +{
> + irq_set_chip_and_handler(irq, &plic_chip, handle_simple_irq);
> + irq_set_chip_data(irq, NULL);
> + irq_set_noprobe(irq);
> + return 0;
> +}
> +
> +static const struct irq_domain_ops plic_irqdomain_ops = {
> + .map = plic_irqdomain_map,
> + .xlate = irq_domain_xlate_onecell,
> +};
> +
> +static struct irq_domain *plic_irqdomain;
> +
> +/*
> + * Handling an interrupt is a two-step process: first you claim the interrupt
> + * by reading the claim register, then you complete the interrupt by writing
> + * 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)
> +{
> + struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
> + void __iomem *claim = plic_hart_offset(handler->ctxid) + CONTEXT_CLAIM;
> + irq_hw_number_t hwirq;
> +
> + WARN_ON_ONCE(!handler->present);
> +
> + csr_clear(sie, SIE_SEIE);
> + while ((hwirq = readl(claim))) {
> + int irq = irq_find_mapping(plic_irqdomain, hwirq);
> +
> + if (unlikely(irq <= 0))
> + pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
> + hwirq);
> + else
> + generic_handle_irq(irq);
> + writel(hwirq, claim);
> + }
> + csr_set(sie, SIE_SEIE);
> +}
> +
> +/*
> + * Walk up the DT tree until we find a active RISC-V core (HART) node and
/s/a/an

> + * extract the cpuid from it.
> + */
> +static int plic_find_hart_id(struct device_node *node)
> +{
> + for (; node; node = node->parent) {
> + if (of_device_is_compatible(node, "riscv"))
> + return riscv_of_processor_hart(node);
> + }
> +
> + return -1;
> +}
> +
> +static int __init plic_init(struct device_node *node,
> + struct device_node *parent)
> +{
> + int error = 0, nr_handlers, nr_mapped = 0, i;
> + u32 nr_irqs;
> +
> + if (plic_regs) {
> + pr_warn("PLIC already present.\n");
> + return -ENXIO;
> + }
> +
> + plic_regs = of_iomap(node, 0);
> + if (WARN_ON(!plic_regs))
> + return -EIO;
> +
> + error = -EINVAL;
> + of_property_read_u32(node, "riscv,ndev", &nr_irqs);
> + if (WARN_ON(!nr_irqs))
> + goto out_iounmap;
> +
> + nr_handlers = of_irq_count(node);
> + if (WARN_ON(!nr_handlers))
> + goto out_iounmap;
> + if (WARN_ON(nr_handlers < num_possible_cpus()))
> + goto out_iounmap;
> +
> + error = -ENOMEM;
> + plic_irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
> + &plic_irqdomain_ops, NULL);
> + if (WARN_ON(!plic_irqdomain))
> + goto out_iounmap;
> +
> + for (i = 0; i < nr_handlers; i++) {
> + struct of_phandle_args parent;
> + struct plic_handler *handler;
> + irq_hw_number_t hwirq;
> + int cpu;
> +
> + if (of_irq_parse_one(node, i, &parent)) {
> + pr_err("failed to parse parent for context %d.\n", i);
> + continue;
> + }
> +
> + /* skip context holes */
> + if (parent.args[0] == -1)
> + continue;
> +
> + cpu = plic_find_hart_id(parent.np);
> + if (cpu < 0) {
> + pr_warn("failed to parse hart ID for context %d.\n", i);
> + continue;
> + }
> +
> + handler = per_cpu_ptr(&plic_handlers, cpu);
> + handler->present = true;
> + handler->ctxid = i;
> +
> + /* priority must be > threshold to trigger an interrupt */
> + writel(0, plic_hart_offset(i) + CONTEXT_THRESHOLD);
> + for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
> + plic_toggle(i, hwirq, 0);
> + nr_mapped++;
> + }
> +
> + pr_info("mapped %d interrupts to %d (out of %d) handlers.\n",
> + nr_irqs, nr_mapped, nr_handlers);
> + set_handle_irq(plic_handle_irq);
> + return 0;
> +
> +out_iounmap:
> + iounmap(plic_regs);
> + return error;
> +}
> +
> +IRQCHIP_DECLARE(sifive_plic0, "sifive,u5-plic", plic_init);
Should it be sifive,u54-plic ?

> +IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */
>

Otherwise, Looks good to me. FWIW..
Reviewed-by: Atish Patra <atish.patra@wdc.com>

Regards,
Atish

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