linux/arch/riscv/kernel/smpboot.c
Christoph Hellwig fcdc653751 riscv: provide native clint access for M-mode
RISC-V has the concept of a cpu level interrupt controller.  The
interface for it is split between a standardized part that is exposed
as bits in the mstatus/sstatus register and the mie/mip/sie/sip
CRS.  But the bit to actually trigger IPIs is not standardized and
just mentioned as implementable using MMIO.

Add support for IPIs using MMIO using the SiFive clint layout (which
is also shared by Ariane, Kendryte and the Qemu virt platform).
Additionally the MMIO block also supports the time value and timer
compare registers, so they are also set up using the same OF node.
Support for other layouts should also be relatively easy to add in the
future.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Anup Patel <anup@brainfault.org>
[paul.walmsley@sifive.com: update include guard format; fix checkpatch
 issues; minor commit message cleanup]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
2019-11-17 15:17:39 -08:00

166 lines
3.8 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* SMP initialisation and IPI support
* Based on arch/arm64/kernel/smp.c
*
* Copyright (C) 2012 ARM Ltd.
* Copyright (C) 2015 Regents of the University of California
* Copyright (C) 2017 SiFive
*/
#include <linux/arch_topology.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/percpu.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/irq.h>
#include <linux/of.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/mm.h>
#include <asm/clint.h>
#include <asm/irq.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/sbi.h>
#include <asm/smp.h>
#include "head.h"
void *__cpu_up_stack_pointer[NR_CPUS];
void *__cpu_up_task_pointer[NR_CPUS];
static DECLARE_COMPLETION(cpu_running);
void __init smp_prepare_boot_cpu(void)
{
init_cpu_topology();
}
void __init smp_prepare_cpus(unsigned int max_cpus)
{
int cpuid;
/* This covers non-smp usecase mandated by "nosmp" option */
if (max_cpus == 0)
return;
for_each_possible_cpu(cpuid) {
if (cpuid == smp_processor_id())
continue;
set_cpu_present(cpuid, true);
}
}
void __init setup_smp(void)
{
struct device_node *dn;
int hart;
bool found_boot_cpu = false;
int cpuid = 1;
for_each_of_cpu_node(dn) {
hart = riscv_of_processor_hartid(dn);
if (hart < 0)
continue;
if (hart == cpuid_to_hartid_map(0)) {
BUG_ON(found_boot_cpu);
found_boot_cpu = 1;
continue;
}
if (cpuid >= NR_CPUS) {
pr_warn("Invalid cpuid [%d] for hartid [%d]\n",
cpuid, hart);
break;
}
cpuid_to_hartid_map(cpuid) = hart;
cpuid++;
}
BUG_ON(!found_boot_cpu);
if (cpuid > nr_cpu_ids)
pr_warn("Total number of cpus [%d] is greater than nr_cpus option value [%d]\n",
cpuid, nr_cpu_ids);
for (cpuid = 1; cpuid < nr_cpu_ids; cpuid++) {
if (cpuid_to_hartid_map(cpuid) != INVALID_HARTID)
set_cpu_possible(cpuid, true);
}
}
int __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
int ret = 0;
int hartid = cpuid_to_hartid_map(cpu);
tidle->thread_info.cpu = cpu;
/*
* On RISC-V systems, all harts boot on their own accord. Our _start
* selects the first hart to boot the kernel and causes the remainder
* of the harts to spin in a loop waiting for their stack pointer to be
* setup by that main hart. Writing __cpu_up_stack_pointer signals to
* the spinning harts that they can continue the boot process.
*/
smp_mb();
WRITE_ONCE(__cpu_up_stack_pointer[hartid],
task_stack_page(tidle) + THREAD_SIZE);
WRITE_ONCE(__cpu_up_task_pointer[hartid], tidle);
lockdep_assert_held(&cpu_running);
wait_for_completion_timeout(&cpu_running,
msecs_to_jiffies(1000));
if (!cpu_online(cpu)) {
pr_crit("CPU%u: failed to come online\n", cpu);
ret = -EIO;
}
return ret;
}
void __init smp_cpus_done(unsigned int max_cpus)
{
}
/*
* C entry point for a secondary processor.
*/
asmlinkage __visible void __init smp_callin(void)
{
struct mm_struct *mm = &init_mm;
if (!IS_ENABLED(CONFIG_RISCV_SBI))
clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
/* All kernel threads share the same mm context. */
mmgrab(mm);
current->active_mm = mm;
trap_init();
notify_cpu_starting(smp_processor_id());
update_siblings_masks(smp_processor_id());
set_cpu_online(smp_processor_id(), 1);
/*
* Remote TLB flushes are ignored while the CPU is offline, so emit
* a local TLB flush right now just in case.
*/
local_flush_tlb_all();
complete(&cpu_running);
/*
* Disable preemption before enabling interrupts, so we don't try to
* schedule a CPU that hasn't actually started yet.
*/
preempt_disable();
local_irq_enable();
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}