linux/arch/arm/mach-omap2/omap-smp.c
Stephen Boyd 7fa22bd546 ARM: 6993/1: platsmp: Allow secondary cpu hotplug with maxcpus=1
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>
2011-07-07 14:45:07 +01:00

136 lines
3.2 KiB
C

/*
* OMAP4 SMP source file. It contains platform specific fucntions
* needed for the linux smp kernel.
*
* Copyright (C) 2009 Texas Instruments, Inc.
*
* Author:
* Santosh Shilimkar <santosh.shilimkar@ti.com>
*
* Platform file needed for the OMAP4 SMP. This file is based on arm
* realview smp platform.
* * Copyright (c) 2002 ARM Limited.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/init.h>
#include <linux/device.h>
#include <linux/smp.h>
#include <linux/io.h>
#include <asm/cacheflush.h>
#include <asm/hardware/gic.h>
#include <asm/smp_scu.h>
#include <mach/hardware.h>
#include <mach/omap4-common.h>
/* SCU base address */
static void __iomem *scu_base;
static DEFINE_SPINLOCK(boot_lock);
void __cpuinit platform_secondary_init(unsigned int cpu)
{
/*
* If any interrupts are already enabled for the primary
* core (e.g. timer irq), then they will not have been enabled
* for us: do so
*/
gic_secondary_init(0);
/*
* Synchronise with the boot thread.
*/
spin_lock(&boot_lock);
spin_unlock(&boot_lock);
}
int __cpuinit boot_secondary(unsigned int cpu, struct task_struct *idle)
{
/*
* Set synchronisation state between this boot processor
* and the secondary one
*/
spin_lock(&boot_lock);
/*
* Update the AuxCoreBoot0 with boot state for secondary core.
* omap_secondary_startup() routine will hold the secondary core till
* the AuxCoreBoot1 register is updated with cpu state
* A barrier is added to ensure that write buffer is drained
*/
omap_modify_auxcoreboot0(0x200, 0xfffffdff);
flush_cache_all();
smp_wmb();
gic_raise_softirq(cpumask_of(cpu), 1);
/*
* Now the secondary core is starting up let it run its
* calibrations, then wait for it to finish
*/
spin_unlock(&boot_lock);
return 0;
}
static void __init wakeup_secondary(void)
{
/*
* Write the address of secondary startup routine into the
* AuxCoreBoot1 where ROM code will jump and start executing
* on secondary core once out of WFE
* A barrier is added to ensure that write buffer is drained
*/
omap_auxcoreboot_addr(virt_to_phys(omap_secondary_startup));
smp_wmb();
/*
* Send a 'sev' to wake the secondary core from WFE.
* Drain the outstanding writes to memory
*/
dsb_sev();
mb();
}
/*
* Initialise the CPU possible map early - this describes the CPUs
* which may be present or become present in the system.
*/
void __init smp_init_cpus(void)
{
unsigned int i, ncores;
/* Never released */
scu_base = ioremap(OMAP44XX_SCU_BASE, SZ_256);
BUG_ON(!scu_base);
ncores = scu_get_core_count(scu_base);
/* sanity check */
if (ncores > NR_CPUS) {
printk(KERN_WARNING
"OMAP4: no. of cores (%d) greater than configured "
"maximum of %d - clipping\n",
ncores, NR_CPUS);
ncores = NR_CPUS;
}
for (i = 0; i < ncores; i++)
set_cpu_possible(i, true);
set_smp_cross_call(gic_raise_softirq);
}
void __init platform_smp_prepare_cpus(unsigned int max_cpus)
{
/*
* Initialise the SCU and wake up the secondary core using
* wakeup_secondary().
*/
scu_enable(scu_base);
wakeup_secondary();
}