7fa22bd546
If an ARM system has multiple cpus in the same socket and the kernel is booted with maxcpus=1, secondary cpus are possible but not present due to how platform_smp_prepare_cpus() is called. Since most typical ARM processors don't actually support physical hotplug, initialize the present map to be equal to the possible map in generic ARM SMP code. Also, always call platform_smp_prepare_cpus() as long as max_cpus is non-zero (0 means no SMP) to allow platform code to do any SMP setup. After applying this patch it's possible to boot an ARM system with maxcpus=1 on the command line and then hotplug in secondary cpus via sysfs. This is more in line with how x86 does things. Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Cc: David Brown <davidb@codeaurora.org> Cc: Tony Lindgren <tony@atomide.com> Cc: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com> Cc: Linus Walleij <linus.walleij@stericsson.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
167 lines
3.9 KiB
C
167 lines
3.9 KiB
C
/* linux/arch/arm/mach-exynos4/platsmp.c
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*
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* Copyright (c) 2010-2011 Samsung Electronics Co., Ltd.
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* http://www.samsung.com
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*
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* Cloned from linux/arch/arm/mach-vexpress/platsmp.c
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*
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* Copyright (C) 2002 ARM Ltd.
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/init.h>
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#include <linux/errno.h>
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/jiffies.h>
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#include <linux/smp.h>
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#include <linux/io.h>
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#include <asm/cacheflush.h>
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#include <asm/hardware/gic.h>
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#include <asm/smp_scu.h>
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#include <asm/unified.h>
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#include <mach/hardware.h>
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#include <mach/regs-clock.h>
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extern void exynos4_secondary_startup(void);
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/*
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* control for which core is the next to come out of the secondary
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* boot "holding pen"
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*/
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volatile int __cpuinitdata pen_release = -1;
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/*
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* Write pen_release in a way that is guaranteed to be visible to all
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* observers, irrespective of whether they're taking part in coherency
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* or not. This is necessary for the hotplug code to work reliably.
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*/
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static void write_pen_release(int val)
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{
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pen_release = val;
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smp_wmb();
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__cpuc_flush_dcache_area((void *)&pen_release, sizeof(pen_release));
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outer_clean_range(__pa(&pen_release), __pa(&pen_release + 1));
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}
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static void __iomem *scu_base_addr(void)
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{
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return (void __iomem *)(S5P_VA_SCU);
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}
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static DEFINE_SPINLOCK(boot_lock);
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void __cpuinit platform_secondary_init(unsigned int cpu)
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{
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/*
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* if any interrupts are already enabled for the primary
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* core (e.g. timer irq), then they will not have been enabled
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* for us: do so
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*/
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gic_secondary_init(0);
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/*
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* let the primary processor know we're out of the
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* pen, then head off into the C entry point
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*/
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write_pen_release(-1);
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/*
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* Synchronise with the boot thread.
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*/
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spin_lock(&boot_lock);
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spin_unlock(&boot_lock);
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}
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int __cpuinit boot_secondary(unsigned int cpu, struct task_struct *idle)
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{
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unsigned long timeout;
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/*
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* Set synchronisation state between this boot processor
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* and the secondary one
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*/
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spin_lock(&boot_lock);
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/*
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* The secondary processor is waiting to be released from
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* the holding pen - release it, then wait for it to flag
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* that it has been released by resetting pen_release.
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*
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* Note that "pen_release" is the hardware CPU ID, whereas
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* "cpu" is Linux's internal ID.
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*/
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write_pen_release(cpu);
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/*
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* Send the secondary CPU a soft interrupt, thereby causing
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* the boot monitor to read the system wide flags register,
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* and branch to the address found there.
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*/
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gic_raise_softirq(cpumask_of(cpu), 1);
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timeout = jiffies + (1 * HZ);
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while (time_before(jiffies, timeout)) {
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smp_rmb();
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if (pen_release == -1)
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break;
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udelay(10);
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}
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/*
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* now the secondary core is starting up let it run its
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* calibrations, then wait for it to finish
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*/
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spin_unlock(&boot_lock);
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return pen_release != -1 ? -ENOSYS : 0;
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}
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/*
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* Initialise the CPU possible map early - this describes the CPUs
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* which may be present or become present in the system.
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*/
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void __init smp_init_cpus(void)
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{
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void __iomem *scu_base = scu_base_addr();
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unsigned int i, ncores;
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ncores = scu_base ? scu_get_core_count(scu_base) : 1;
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/* sanity check */
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if (ncores > NR_CPUS) {
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printk(KERN_WARNING
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"EXYNOS4: no. of cores (%d) greater than configured "
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"maximum of %d - clipping\n",
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ncores, NR_CPUS);
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ncores = NR_CPUS;
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}
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for (i = 0; i < ncores; i++)
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set_cpu_possible(i, true);
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set_smp_cross_call(gic_raise_softirq);
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}
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void __init platform_smp_prepare_cpus(unsigned int max_cpus)
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{
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scu_enable(scu_base_addr());
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/*
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* Write the address of secondary startup into the
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* system-wide flags register. The boot monitor waits
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* until it receives a soft interrupt, and then the
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* secondary CPU branches to this address.
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*/
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__raw_writel(BSYM(virt_to_phys(exynos4_secondary_startup)), S5P_VA_SYSRAM);
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}
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