linux/drivers/irqchip/irq-sifive-plic.c
Anup Patel cc9f04f9a8 irqchip/sifive-plic: Implement irq_set_affinity() for SMP host
Currently on SMP host, all CPUs take external interrupts routed via
PLIC. All CPUs will try to claim a given external interrupt but only
one of them will succeed while other CPUs would simply resume whatever
they were doing before. This means if we have N CPUs then for every
external interrupt N-1 CPUs will always fail to claim it and waste
their CPU time.

Instead of above, external interrupts should be taken by only one CPU
and we should have provision to explicitly specify IRQ affinity from
kernel-space or user-space.

This patch provides irq_set_affinity() implementation for PLIC driver.
It also updates irq_enable() such that PLIC interrupts are only enabled
for one of CPUs specified in IRQ affinity mask.

With this patch in-place, we can change IRQ affinity at any-time from
user-space using procfs.

Example:

/ # cat /proc/interrupts
           CPU0       CPU1       CPU2       CPU3
  8:         44          0          0          0  SiFive PLIC   8  virtio0
 10:         48          0          0          0  SiFive PLIC  10  ttyS0
IPI0:        55        663         58        363  Rescheduling interrupts
IPI1:         0          1          3         16  Function call interrupts
/ #
/ #
/ # echo 4 > /proc/irq/10/smp_affinity
/ #
/ # cat /proc/interrupts
           CPU0       CPU1       CPU2       CPU3
  8:         45          0          0          0  SiFive PLIC   8  virtio0
 10:        160          0         17          0  SiFive PLIC  10  ttyS0
IPI0:        68        693         77        410  Rescheduling interrupts
IPI1:         0          2          3         16  Function call interrupts

Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
2019-02-21 10:32:21 +00:00

301 lines
7.5 KiB
C

// 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>
#include <asm/smp.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 'sifive,plic-1.0.0', 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;
void __iomem *hart_base;
/*
* Protect mask operations on the registers given that we can't
* assume atomic memory operations work on them.
*/
raw_spinlock_t enable_lock;
void __iomem *enable_base;
};
static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
static inline void plic_toggle(struct plic_handler *handler,
int hwirq, int enable)
{
u32 __iomem *reg = handler->enable_base + (hwirq / 32) * sizeof(u32);
u32 hwirq_mask = 1 << (hwirq % 32);
raw_spin_lock(&handler->enable_lock);
if (enable)
writel(readl(reg) | hwirq_mask, reg);
else
writel(readl(reg) & ~hwirq_mask, reg);
raw_spin_unlock(&handler->enable_lock);
}
static inline void plic_irq_toggle(const struct cpumask *mask,
int hwirq, int enable)
{
int cpu;
writel(enable, plic_regs + PRIORITY_BASE + hwirq * PRIORITY_PER_ID);
for_each_cpu(cpu, mask) {
struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
if (handler->present)
plic_toggle(handler, hwirq, enable);
}
}
static void plic_irq_enable(struct irq_data *d)
{
unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
cpu_online_mask);
if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
return;
plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
}
static void plic_irq_disable(struct irq_data *d)
{
plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
}
#ifdef CONFIG_SMP
static int plic_set_affinity(struct irq_data *d,
const struct cpumask *mask_val, bool force)
{
unsigned int cpu;
if (force)
cpu = cpumask_first(mask_val);
else
cpu = cpumask_any_and(mask_val, cpu_online_mask);
if (cpu >= nr_cpu_ids)
return -EINVAL;
if (!irqd_irq_disabled(d)) {
plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
}
irq_data_update_effective_affinity(d, cpumask_of(cpu));
return IRQ_SET_MASK_OK_DONE;
}
#endif
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,
#ifdef CONFIG_SMP
.irq_set_affinity = plic_set_affinity,
#endif
};
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 = handler->hart_base + 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 an active RISC-V core (HART) node and
* 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_hartid(node);
}
return -1;
}
static int __init plic_init(struct device_node *node,
struct device_node *parent)
{
int error = 0, nr_contexts, nr_handlers = 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_contexts = of_irq_count(node);
if (WARN_ON(!nr_contexts))
goto out_iounmap;
if (WARN_ON(nr_contexts < 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_contexts; i++) {
struct of_phandle_args parent;
struct plic_handler *handler;
irq_hw_number_t hwirq;
int cpu, hartid;
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;
hartid = plic_find_hart_id(parent.np);
if (hartid < 0) {
pr_warn("failed to parse hart ID for context %d.\n", i);
continue;
}
cpu = riscv_hartid_to_cpuid(hartid);
if (cpu < 0) {
pr_warn("Invalid cpuid for context %d\n", i);
continue;
}
handler = per_cpu_ptr(&plic_handlers, cpu);
if (handler->present) {
pr_warn("handler already present for context %d.\n", i);
continue;
}
handler->present = true;
handler->hart_base =
plic_regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
raw_spin_lock_init(&handler->enable_lock);
handler->enable_base =
plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
/* priority must be > threshold to trigger an interrupt */
writel(0, handler->hart_base + CONTEXT_THRESHOLD);
for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
plic_toggle(handler, hwirq, 0);
nr_handlers++;
}
pr_info("mapped %d interrupts with %d handlers for %d contexts.\n",
nr_irqs, nr_handlers, nr_contexts);
set_handle_irq(plic_handle_irq);
return 0;
out_iounmap:
iounmap(plic_regs);
return error;
}
IRQCHIP_DECLARE(sifive_plic, "sifive,plic-1.0.0", plic_init);
IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */