[RFC PATCH 2/2] ARM: SMP support for mach-virt
Will Deacon
will.deacon at arm.com
Mon Dec 3 12:52:40 EST 2012
From: Marc Zyngier <marc.zyngier at arm.com>
This patch adds support for SMP to mach-virt.
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
---
arch/arm/mach-virt/Makefile | 1 +
arch/arm/mach-virt/headsmp.S | 38 ++++++++
arch/arm/mach-virt/platsmp.c | 205 +++++++++++++++++++++++++++++++++++++++++++
arch/arm/mach-virt/virt.c | 6 ++
4 files changed, 250 insertions(+)
create mode 100644 arch/arm/mach-virt/headsmp.S
create mode 100644 arch/arm/mach-virt/platsmp.c
diff --git a/arch/arm/mach-virt/Makefile b/arch/arm/mach-virt/Makefile
index 7ddbfa6..9ce8a28 100644
--- a/arch/arm/mach-virt/Makefile
+++ b/arch/arm/mach-virt/Makefile
@@ -3,3 +3,4 @@
#
obj-y := virt.o
+obj-$(CONFIG_SMP) += platsmp.o headsmp.o
diff --git a/arch/arm/mach-virt/headsmp.S b/arch/arm/mach-virt/headsmp.S
new file mode 100644
index 0000000..e27afb0
--- /dev/null
+++ b/arch/arm/mach-virt/headsmp.S
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2012 ARM Limited
+ * 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/linkage.h>
+#include <linux/init.h>
+
+ __INIT
+
+/*
+ * This provides a "holding pen" into which all secondary cores are held
+ * until we're ready for them to initialise.
+ */
+ENTRY(virt_secondary_startup)
+ mrc p15, 0, r0, c0, c0, 5
+ and r0, r0, #15
+ adr r4, 1f
+ ldmia r4, {r5, r6}
+ sub r4, r4, r5
+ add r6, r6, r4
+pen: ldr r7, [r6]
+ cmp r7, r0
+ bne pen
+
+ /*
+ * we've been released from the holding pen: secondary_stack
+ * should now contain the SVC stack for this core
+ */
+ b secondary_startup
+
+ .align
+1: .long .
+ .long pen_release
+ENDPROC(virt_secondary_startup)
diff --git a/arch/arm/mach-virt/platsmp.c b/arch/arm/mach-virt/platsmp.c
new file mode 100644
index 0000000..fe02f51
--- /dev/null
+++ b/arch/arm/mach-virt/platsmp.c
@@ -0,0 +1,205 @@
+/*
+ * Dummy Virtual Machine - does what it says on the tin.
+ *
+ * SMP operations, shamelessly stolen from:
+ * arch/arm64/kernel/smp.c
+ *
+ * Copyright (C) 2012 ARM Ltd
+ * Author: Catalin Marinas <catalin.marinas at arm.com>
+ * Author: Will Deacon <will.deacon at arm.com>
+ * Author: Marc Zyngier <marc.zyngier at arm.com>
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/smp.h>
+#include <linux/errno.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/jiffies.h>
+#include <linux/of.h>
+
+#include <asm/cacheflush.h>
+#include <asm/smp_plat.h>
+#include <asm/hardware/gic.h>
+
+extern void virt_secondary_startup(void);
+
+static DEFINE_RAW_SPINLOCK(boot_lock);
+static phys_addr_t cpu_release_addr[NR_CPUS];
+
+/*
+ * Write secondary_holding_pen_release in a way that is guaranteed to be
+ * visible to all observers, irrespective of whether they're taking part
+ * in coherency or not. This is necessary for the hotplug code to work
+ * reliably.
+ */
+static void __cpuinit write_pen_release(int val)
+{
+ void *start = (void *)&pen_release;
+ unsigned long size = sizeof(pen_release);
+
+ pen_release = val;
+ smp_wmb();
+ __cpuc_flush_dcache_area(start, size);
+ outer_clean_range(__pa(&pen_release), __pa(&pen_release + 1));
+}
+
+/*
+ * Enumerate the possible CPU set from the device tree.
+ */
+static void __init virt_smp_init_cpus(void)
+{
+ const char *enable_method;
+ struct device_node *dn = NULL;
+ int cpu = 0;
+ u32 release_addr;
+
+ while ((dn = of_find_node_by_type(dn, "cpu"))) {
+ if (cpu >= NR_CPUS)
+ goto next;
+
+ /*
+ * We currently support only the "spin-table" enable-method.
+ */
+ enable_method = of_get_property(dn, "enable-method", NULL);
+ if (!enable_method || strcmp(enable_method, "spin-table")) {
+ pr_err("CPU %d: missing or invalid enable-method property: %s\n",
+ cpu, enable_method);
+ goto next;
+ }
+
+ /*
+ * Determine the address from which the CPU is polling.
+ */
+ if (of_property_read_u32(dn, "cpu-release-addr", &release_addr)) {
+ pr_err("CPU %d: missing or invalid cpu-release-addr property\n",
+ cpu);
+ goto next;
+ }
+
+ cpu_release_addr[cpu] = release_addr;
+ set_cpu_possible(cpu, true);
+next:
+ cpu++;
+ }
+
+ /* sanity check */
+ if (cpu > NR_CPUS)
+ pr_warning("no. of cores (%d) greater than configured maximum of %d - clipping\n",
+ cpu, NR_CPUS);
+
+ set_smp_cross_call(gic_raise_softirq);
+}
+
+static void __init virt_smp_prepare_cpus(unsigned int max_cpus)
+{
+ int cpu;
+ void **release_addr;
+ unsigned int ncores = num_possible_cpus();
+
+ /*
+ * are we trying to boot more cores than exist?
+ */
+ if (max_cpus > ncores)
+ max_cpus = ncores;
+
+ /*
+ * Initialise the present map (which describes the set of CPUs
+ * actually populated at the present time) and release the
+ * secondaries from the bootloader.
+ */
+ for_each_possible_cpu(cpu) {
+ if (max_cpus == 0)
+ break;
+
+ if (!cpu_release_addr[cpu])
+ continue;
+
+ release_addr = __va(cpu_release_addr[cpu]);
+ release_addr[0] = (void *)__pa(virt_secondary_startup);
+ smp_wmb();
+ __cpuc_flush_dcache_area(release_addr, sizeof(release_addr[0]));
+ outer_clean_range(__pa(release_addr), __pa(release_addr+1));
+
+ set_cpu_present(cpu, true);
+ max_cpus--;
+ }
+}
+
+static int __cpuinit virt_boot_secondary(unsigned int cpu,
+ struct task_struct *idle)
+{
+ unsigned long timeout;
+
+ /*
+ * Set synchronisation state between this boot processor
+ * and the secondary one
+ */
+ raw_spin_lock(&boot_lock);
+
+ /*
+ * Update the pen release flag.
+ */
+ write_pen_release(cpu);
+
+ /*
+ * Send the secondary CPU a soft interrupt, causing the
+ * secondaries to read pen_release.
+ */
+ gic_raise_softirq(cpumask_of(cpu), 0);
+
+ timeout = jiffies + (1 * HZ);
+ while (time_before(jiffies, timeout)) {
+ if (pen_release == -1UL)
+ break;
+ udelay(10);
+ }
+
+ /*
+ * Now the secondary core is starting up let it run its
+ * calibrations, then wait for it to finish
+ */
+ raw_spin_unlock(&boot_lock);
+
+ return pen_release != -1 ? -ENOSYS : 0;
+}
+
+static void __cpuinit virt_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);
+
+ /*
+ * let the primary processor know we're out of the
+ * pen, then head off into the C entry point
+ */
+ write_pen_release(-1);
+
+ /*
+ * Synchronise with the boot thread.
+ */
+ raw_spin_lock(&boot_lock);
+ raw_spin_unlock(&boot_lock);
+}
+
+struct smp_operations __initdata virt_smp_ops = {
+ .smp_init_cpus = virt_smp_init_cpus,
+ .smp_prepare_cpus = virt_smp_prepare_cpus,
+ .smp_secondary_init = virt_secondary_init,
+ .smp_boot_secondary = virt_boot_secondary,
+};
diff --git a/arch/arm/mach-virt/virt.c b/arch/arm/mach-virt/virt.c
index 174b9da..d764835 100644
--- a/arch/arm/mach-virt/virt.c
+++ b/arch/arm/mach-virt/virt.c
@@ -20,6 +20,7 @@
#include <linux/of_irq.h>
#include <linux/of_platform.h>
+#include <linux/smp.h>
#include <asm/arch_timer.h>
#include <asm/hardware/gic.h>
@@ -56,10 +57,15 @@ static struct sys_timer virt_timer = {
.init = virt_timer_init,
};
+#ifdef CONFIG_SMP
+extern struct smp_operations virt_smp_ops;
+#endif
+
DT_MACHINE_START(VIRT, "Dummy Virtual Machine")
.init_irq = gic_init_irq,
.handle_irq = gic_handle_irq,
.timer = &virt_timer,
.init_machine = virt_init,
+ .smp = smp_ops(virt_smp_ops),
.dt_compat = virt_dt_match,
MACHINE_END
--
1.8.0
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