diff mbox

[05/10] ARM: zx: bring up the secondary core

Message ID 1426333785-3952-6-git-send-email-jun.nie@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Jun Nie March 14, 2015, 11:49 a.m. UTC
Use release_pen mechanism to bring up the secondary core.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Jun Nie <jun.nie@linaro.org>
---
 arch/arm/mach-zx/Makefile   |   1 +
 arch/arm/mach-zx/core.h     |  17 +++++
 arch/arm/mach-zx/headsmp.S  |  38 ++++++++++++
 arch/arm/mach-zx/platsmp.c  | 147 ++++++++++++++++++++++++++++++++++++++++++++
 arch/arm/mach-zx/zx296702.c |   1 +
 5 files changed, 204 insertions(+)
 create mode 100644 arch/arm/mach-zx/core.h
 create mode 100644 arch/arm/mach-zx/headsmp.S
 create mode 100644 arch/arm/mach-zx/platsmp.c

Comments

Arnd Bergmann March 14, 2015, 9:25 p.m. UTC | #1
On Saturday 14 March 2015 19:49:40 Jun Nie wrote:
> +
> +       /*
> +        * This is really belt and braces; we hold unintended secondary
> +        * CPUs in the holding pen until we're ready for them.  However,
> +        * since we haven't sent them a soft interrupt, they shouldn't
> +        * be there.
> +        */
> +       write_pen_release(cpu);
> +
> 

Why do you need the holding pen on this platform? Is there a firmware
bug or just missing hardware support for proper SMP power management?

	Arnd
Shawn Guo March 16, 2015, 7:23 a.m. UTC | #2
On Sat, Mar 14, 2015 at 10:25:03PM +0100, Arnd Bergmann wrote:
> On Saturday 14 March 2015 19:49:40 Jun Nie wrote:
> > +
> > +       /*
> > +        * This is really belt and braces; we hold unintended secondary
> > +        * CPUs in the holding pen until we're ready for them.  However,
> > +        * since we haven't sent them a soft interrupt, they shouldn't
> > +        * be there.
> > +        */
> > +       write_pen_release(cpu);
> > +
> > 
> 
> Why do you need the holding pen on this platform? Is there a firmware
> bug or just missing hardware support for proper SMP power management?

Arnd,

As this is how things are handled in vendor's kernel, we thought the
hardware might be lack of SMP power management.  But we will check with
vendor to see if there is any level of hardware support for secondary
core management, so that we can save the use of holding pen.

Thanks for the comment.

Shawn
diff mbox

Patch

diff --git a/arch/arm/mach-zx/Makefile b/arch/arm/mach-zx/Makefile
index 7a541c7..7c2edf6 100644
--- a/arch/arm/mach-zx/Makefile
+++ b/arch/arm/mach-zx/Makefile
@@ -1 +1,2 @@ 
 obj-$(CONFIG_SOC_ZX296702) += zx296702.o
+obj-$(CONFIG_SMP) += headsmp.o platsmp.o
diff --git a/arch/arm/mach-zx/core.h b/arch/arm/mach-zx/core.h
new file mode 100644
index 0000000..400c7b4
--- /dev/null
+++ b/arch/arm/mach-zx/core.h
@@ -0,0 +1,17 @@ 
+/*
+ * Copyright 2014 Linaro Ltd.
+ * Copyright (C) 2014 ZTE Corporation.
+ *
+ * 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.
+ */
+
+#ifndef __MACH_ZX_CORE_H
+#define __MACH_ZX_CORE_H
+
+extern struct smp_operations zx_smp_ops;
+
+void zx_secondary_startup(void);
+
+#endif /* __MACH_ZX_CORE_H */
diff --git a/arch/arm/mach-zx/headsmp.S b/arch/arm/mach-zx/headsmp.S
new file mode 100644
index 0000000..8f70ff7
--- /dev/null
+++ b/arch/arm/mach-zx/headsmp.S
@@ -0,0 +1,38 @@ 
+/*
+ * Copyright 2014 Linaro Ltd.
+ * Copyright (C) 2014 ZTE Corporation.
+ *
+ * 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>
+
+/*
+ * zx2967 specific entry point for secondary CPUs.  This provides
+ * a "holding pen" into which all secondary cores are held until we're
+ * ready for them to initialise.
+ */
+ENTRY(zx_secondary_startup)
+	bl	v7_invalidate_l1
+	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
+ENDPROC(zx_secondary_startup)
+
+	.align	2
+1:	.long	.
+	.long	pen_release
diff --git a/arch/arm/mach-zx/platsmp.c b/arch/arm/mach-zx/platsmp.c
new file mode 100644
index 0000000..e508a9c
--- /dev/null
+++ b/arch/arm/mach-zx/platsmp.c
@@ -0,0 +1,147 @@ 
+/*
+ * Copyright 2014 Linaro Ltd.
+ * Copyright (C) 2014 ZTE Corporation.
+ *
+ * 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/delay.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/jiffies.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/smp.h>
+
+#include <asm/cacheflush.h>
+#include <asm/smp_scu.h>
+
+#include "core.h"
+
+#define AON_SYS_CTRL_RESERVED1		0xa8
+
+static DEFINE_SPINLOCK(boot_lock);
+
+void __init zx_smp_prepare_cpus(unsigned int max_cpus)
+{
+	struct device_node *np;
+	unsigned long base = 0;
+	void __iomem *scu_base;
+	void __iomem *aonsysctrl_base;
+
+	base = scu_a9_get_base();
+	scu_base = ioremap(base, SZ_256);
+	if (!scu_base) {
+		pr_err("%s: failed to map scu\n", __func__);
+		return;
+	}
+
+	scu_enable(scu_base);
+	iounmap(scu_base);
+
+	np = of_find_compatible_node(NULL, NULL, "zte,aon-sysctrl");
+	if (!np) {
+		pr_err("%s: failed to find sysctrl node\n", __func__);
+		return;
+	}
+
+	aonsysctrl_base = of_iomap(np, 0);
+	if (!aonsysctrl_base) {
+		pr_err("%s: failed to map aonsysctrl\n", __func__);
+		of_node_put(np);
+		return;
+	}
+
+	/*
+	 * Write the address of secondary startup into the
+	 * system-wide flags register. The BootMonitor waits
+	 * until it receives a soft interrupt, and then the
+	 * secondary CPU branches to this address.
+	 */
+	__raw_writel(virt_to_phys(zx_secondary_startup),
+		     aonsysctrl_base + AON_SYS_CTRL_RESERVED1);
+
+	iounmap(aonsysctrl_base);
+	of_node_put(np);
+}
+
+/*
+ * Write 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 write_pen_release(int val)
+{
+	pen_release = val;
+	/* make sure pen_release is visible */
+	smp_wmb();
+	sync_cache_w(&pen_release);
+}
+
+static void zx_secondary_init(unsigned int cpu)
+{
+	/*
+	 * 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.
+	 */
+	spin_lock(&boot_lock);
+	spin_unlock(&boot_lock);
+}
+
+static int zx_boot_secondary(unsigned int cpu, struct task_struct *idle)
+{
+	unsigned long timeout;
+
+	/*
+	 * Set synchronisation state between this boot processor
+	 * and the secondary one
+	 */
+	spin_lock(&boot_lock);
+
+	/*
+	 * This is really belt and braces; we hold unintended secondary
+	 * CPUs in the holding pen until we're ready for them.  However,
+	 * since we haven't sent them a soft interrupt, they shouldn't
+	 * be there.
+	 */
+	write_pen_release(cpu);
+
+	/*
+	 * 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.
+	 */
+	arch_send_wakeup_ipi_mask(cpumask_of(cpu));
+
+	timeout = jiffies + (1 * HZ);
+	while (time_before(jiffies, timeout)) {
+		/* sync pen_release value */
+		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;
+}
+
+struct smp_operations zx_smp_ops __initdata = {
+	.smp_prepare_cpus	= zx_smp_prepare_cpus,
+	.smp_secondary_init	= zx_secondary_init,
+	.smp_boot_secondary	= zx_boot_secondary,
+};
diff --git a/arch/arm/mach-zx/zx296702.c b/arch/arm/mach-zx/zx296702.c
index 9c055ea..d5d8be6 100644
--- a/arch/arm/mach-zx/zx296702.c
+++ b/arch/arm/mach-zx/zx296702.c
@@ -59,6 +59,7 @@  static const char *zx296702_dt_compat[] __initconst = {
 };
 
 DT_MACHINE_START(ZX, "ZTE ZX296702 (Device Tree)")
+	.smp		= smp_ops(zx_smp_ops),
 	.dt_compat	= zx296702_dt_compat,
 	.init_machine	= zx296702_init_machine,
 MACHINE_END