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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>
136 lines
3.2 KiB
C
136 lines
3.2 KiB
C
/*
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* OMAP4 SMP source file. It contains platform specific fucntions
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* needed for the linux smp kernel.
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*
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* Copyright (C) 2009 Texas Instruments, Inc.
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*
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* Author:
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* Santosh Shilimkar <santosh.shilimkar@ti.com>
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*
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* Platform file needed for the OMAP4 SMP. This file is based on arm
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* realview smp platform.
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* * Copyright (c) 2002 ARM Limited.
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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/device.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 <mach/hardware.h>
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#include <mach/omap4-common.h>
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/* SCU base address */
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static void __iomem *scu_base;
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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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* 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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/*
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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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* Update the AuxCoreBoot0 with boot state for secondary core.
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* omap_secondary_startup() routine will hold the secondary core till
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* the AuxCoreBoot1 register is updated with cpu state
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* A barrier is added to ensure that write buffer is drained
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*/
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omap_modify_auxcoreboot0(0x200, 0xfffffdff);
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flush_cache_all();
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smp_wmb();
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gic_raise_softirq(cpumask_of(cpu), 1);
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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 0;
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}
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static void __init wakeup_secondary(void)
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{
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/*
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* Write the address of secondary startup routine into the
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* AuxCoreBoot1 where ROM code will jump and start executing
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* on secondary core once out of WFE
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* A barrier is added to ensure that write buffer is drained
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*/
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omap_auxcoreboot_addr(virt_to_phys(omap_secondary_startup));
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smp_wmb();
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/*
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* Send a 'sev' to wake the secondary core from WFE.
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* Drain the outstanding writes to memory
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*/
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dsb_sev();
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mb();
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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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unsigned int i, ncores;
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/* Never released */
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scu_base = ioremap(OMAP44XX_SCU_BASE, SZ_256);
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BUG_ON(!scu_base);
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ncores = scu_get_core_count(scu_base);
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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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"OMAP4: 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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/*
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* Initialise the SCU and wake up the secondary core using
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* wakeup_secondary().
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*/
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scu_enable(scu_base);
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wakeup_secondary();
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}
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