linux/arch/arm/mach-msm/platsmp.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

161 lines
3.9 KiB
C

/*
* Copyright (C) 2002 ARM Ltd.
* All Rights Reserved
* Copyright (c) 2010, Code Aurora Forum. All rights reserved.
*
* 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/errno.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/jiffies.h>
#include <linux/smp.h>
#include <linux/io.h>
#include <asm/hardware/gic.h>
#include <asm/cacheflush.h>
#include <asm/mach-types.h>
#include <mach/msm_iomap.h>
#include "scm-boot.h"
#define VDD_SC1_ARRAY_CLAMP_GFS_CTL 0x15A0
#define SCSS_CPU1CORE_RESET 0xD80
#define SCSS_DBG_STATUS_CORE_PWRDUP 0xE64
/* Mask for edge trigger PPIs except AVS_SVICINT and AVS_SVICINTSWDONE */
#define GIC_PPI_EDGE_MASK 0xFFFFD7FF
extern void msm_secondary_startup(void);
/*
* control for which core is the next to come out of the secondary
* boot "holding pen".
*/
volatile int pen_release = -1;
static DEFINE_SPINLOCK(boot_lock);
void __cpuinit platform_secondary_init(unsigned int cpu)
{
/* Configure edge-triggered PPIs */
writel(GIC_PPI_EDGE_MASK, MSM_QGIC_DIST_BASE + GIC_DIST_CONFIG + 4);
/*
* 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);
/*
* let the primary processor know we're out of the
* pen, then head off into the C entry point
*/
pen_release = -1;
smp_wmb();
/*
* Synchronise with the boot thread.
*/
spin_lock(&boot_lock);
spin_unlock(&boot_lock);
}
static __cpuinit void prepare_cold_cpu(unsigned int cpu)
{
int ret;
ret = scm_set_boot_addr(virt_to_phys(msm_secondary_startup),
SCM_FLAG_COLDBOOT_CPU1);
if (ret == 0) {
void *sc1_base_ptr;
sc1_base_ptr = ioremap_nocache(0x00902000, SZ_4K*2);
if (sc1_base_ptr) {
writel(0, sc1_base_ptr + VDD_SC1_ARRAY_CLAMP_GFS_CTL);
writel(0, sc1_base_ptr + SCSS_CPU1CORE_RESET);
writel(3, sc1_base_ptr + SCSS_DBG_STATUS_CORE_PWRDUP);
iounmap(sc1_base_ptr);
}
} else
printk(KERN_DEBUG "Failed to set secondary core boot "
"address\n");
}
int __cpuinit boot_secondary(unsigned int cpu, struct task_struct *idle)
{
unsigned long timeout;
static int cold_boot_done;
/* Only need to bring cpu out of reset this way once */
if (cold_boot_done == false) {
prepare_cold_cpu(cpu);
cold_boot_done = true;
}
/*
* set synchronisation state between this boot processor
* and the secondary one
*/
spin_lock(&boot_lock);
/*
* The secondary processor is waiting to be released from
* the holding pen - release it, then wait for it to flag
* that it has been released by resetting pen_release.
*
* Note that "pen_release" is the hardware CPU ID, whereas
* "cpu" is Linux's internal ID.
*/
pen_release = cpu;
__cpuc_flush_dcache_area((void *)&pen_release, sizeof(pen_release));
outer_clean_range(__pa(&pen_release), __pa(&pen_release + 1));
/*
* Send the secondary CPU a soft interrupt, thereby causing
* the boot monitor to read the system wide flags register,
* and branch to the address found there.
*/
gic_raise_softirq(cpumask_of(cpu), 1);
timeout = jiffies + (1 * HZ);
while (time_before(jiffies, timeout)) {
smp_rmb();
if (pen_release == -1)
break;
udelay(10);
}
/*
* now the secondary core is starting up let it run its
* calibrations, then wait for it to finish
*/
spin_unlock(&boot_lock);
return pen_release != -1 ? -ENOSYS : 0;
}
/*
* Initialise the CPU possible map early - this describes the CPUs
* which may be present or become present in the system. The msm8x60
* does not support the ARM SCU, so just set the possible cpu mask to
* NR_CPUS.
*/
void __init smp_init_cpus(void)
{
unsigned int i;
for (i = 0; i < NR_CPUS; i++)
set_cpu_possible(i, true);
set_smp_cross_call(gic_raise_softirq);
}
void __init platform_smp_prepare_cpus(unsigned int max_cpus)
{
}