ARM: vexpress/TC2: basic PM support

This is the MCPM backend for the Virtual Express A15x2 A7x3 CoreTile
aka TC2.  This provides cluster management for SMP secondary boot and
CPU hotplug.
Signed-off-by: NNicolas Pitre <nico@linaro.org>
Acked-by: NPawel Moll <pawel.moll@arm.com>
Reviewed-by: NLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
[PM: made it drive SCC registers directly and provide base for SPC]
Signed-off-by: NPawel Moll <pawel.moll@arm.com>

arch/arm/mach-vexpress/Kconfig

@@ -66,4 +66,12 @@ config ARCH_VEXPRESS_DCSCB
 	  This is needed to provide CPU and cluster power management
 	  on RTSM implementing big.LITTLE.
 
+config ARCH_VEXPRESS_TC2_PM
+	bool "Versatile Express TC2 power management"
+	depends on MCPM
+	select ARM_CCI
+	help
+	  Support for CPU and cluster power management on Versatile Express
+	  with a TC2 (A15x2 A7x3) big.LITTLE core tile.
+
 endmenu

arch/arm/mach-vexpress/Makefile

@@ -7,5 +7,6 @@ ccflags-$(CONFIG_ARCH_MULTIPLATFORM) := -I$(srctree)/$(src)/include \
 obj-y					:= v2m.o
 obj-$(CONFIG_ARCH_VEXPRESS_CA9X4)	+= ct-ca9x4.o
 obj-$(CONFIG_ARCH_VEXPRESS_DCSCB)	+= dcscb.o	dcscb_setup.o
+obj-$(CONFIG_ARCH_VEXPRESS_TC2_PM)	+= tc2_pm.o spc.o
 obj-$(CONFIG_SMP)			+= platsmp.o
 obj-$(CONFIG_HOTPLUG_CPU)		+= hotplug.o

arch/arm/mach-vexpress/tc2_pm.c

+/*
+ * arch/arm/mach-vexpress/tc2_pm.c - TC2 power management support
+ *
+ * Created by:	Nicolas Pitre, October 2012
+ * Copyright:	(C) 2012-2013  Linaro Limited
+ *
+ * Some portions of this file were originally written by Achin Gupta
+ * Copyright:   (C) 2012  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/io.h>
+#include <linux/kernel.h>
+#include <linux/of_address.h>
+#include <linux/spinlock.h>
+#include <linux/errno.h>
+
+#include <asm/mcpm.h>
+#include <asm/proc-fns.h>
+#include <asm/cacheflush.h>
+#include <asm/cputype.h>
+#include <asm/cp15.h>
+
+#include <linux/arm-cci.h>
+
+#include "spc.h"
+
+/* SCC conf registers */
+#define A15_CONF		0x400
+#define A7_CONF			0x500
+#define SYS_INFO		0x700
+#define SPC_BASE		0xb00
+
+/*
+ * We can't use regular spinlocks. In the switcher case, it is possible
+ * for an outbound CPU to call power_down() after its inbound counterpart
+ * is already live using the same logical CPU number which trips lockdep
+ * debugging.
+ */
+static arch_spinlock_t tc2_pm_lock = __ARCH_SPIN_LOCK_UNLOCKED;
+
+#define TC2_CLUSTERS			2
+#define TC2_MAX_CPUS_PER_CLUSTER	3
+
+static unsigned int tc2_nr_cpus[TC2_CLUSTERS];
+
+/* Keep per-cpu usage count to cope with unordered up/down requests */
+static int tc2_pm_use_count[TC2_MAX_CPUS_PER_CLUSTER][TC2_CLUSTERS];
+
+#define tc2_cluster_unused(cluster) \
+	(!tc2_pm_use_count[0][cluster] && \
+	 !tc2_pm_use_count[1][cluster] && \
+	 !tc2_pm_use_count[2][cluster])
+
+static int tc2_pm_power_up(unsigned int cpu, unsigned int cluster)
+{
+	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
+	if (cluster >= TC2_CLUSTERS || cpu >= tc2_nr_cpus[cluster])
+		return -EINVAL;
+
+	/*
+	 * Since this is called with IRQs enabled, and no arch_spin_lock_irq
+	 * variant exists, we need to disable IRQs manually here.
+	 */
+	local_irq_disable();
+	arch_spin_lock(&tc2_pm_lock);
+
+	if (tc2_cluster_unused(cluster))
+		ve_spc_powerdown(cluster, false);
+
+	tc2_pm_use_count[cpu][cluster]++;
+	if (tc2_pm_use_count[cpu][cluster] == 1) {
+		ve_spc_set_resume_addr(cluster, cpu,
+				       virt_to_phys(mcpm_entry_point));
+		ve_spc_cpu_wakeup_irq(cluster, cpu, true);
+	} else if (tc2_pm_use_count[cpu][cluster] != 2) {
+		/*
+		 * The only possible values are:
+		 * 0 = CPU down
+		 * 1 = CPU (still) up
+		 * 2 = CPU requested to be up before it had a chance
+		 *     to actually make itself down.
+		 * Any other value is a bug.
+		 */
+		BUG();
+	}
+
+	arch_spin_unlock(&tc2_pm_lock);
+	local_irq_enable();
+
+	return 0;
+}
+
+static void tc2_pm_power_down(void)
+{
+	unsigned int mpidr, cpu, cluster;
+	bool last_man = false, skip_wfi = false;
+
+	mpidr = read_cpuid_mpidr();
+	cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
+	cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
+
+	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
+	BUG_ON(cluster >= TC2_CLUSTERS || cpu >= TC2_MAX_CPUS_PER_CLUSTER);
+
+	__mcpm_cpu_going_down(cpu, cluster);
+
+	arch_spin_lock(&tc2_pm_lock);
+	BUG_ON(__mcpm_cluster_state(cluster) != CLUSTER_UP);
+	tc2_pm_use_count[cpu][cluster]--;
+	if (tc2_pm_use_count[cpu][cluster] == 0) {
+		ve_spc_cpu_wakeup_irq(cluster, cpu, true);
+		if (tc2_cluster_unused(cluster)) {
+			ve_spc_powerdown(cluster, true);
+			ve_spc_global_wakeup_irq(true);
+			last_man = true;
+		}
+	} else if (tc2_pm_use_count[cpu][cluster] == 1) {
+		/*
+		 * A power_up request went ahead of us.
+		 * Even if we do not want to shut this CPU down,
+		 * the caller expects a certain state as if the WFI
+		 * was aborted.  So let's continue with cache cleaning.
+		 */
+		skip_wfi = true;
+	} else
+		BUG();
+
+	if (last_man && __mcpm_outbound_enter_critical(cpu, cluster)) {
+		arch_spin_unlock(&tc2_pm_lock);
+
+		if (read_cpuid_part_number() == ARM_CPU_PART_CORTEX_A15) {
+			/*
+			 * On the Cortex-A15 we need to disable
+			 * L2 prefetching before flushing the cache.
+			 */
+			asm volatile(
+			"mcr	p15, 1, %0, c15, c0, 3 \n\t"
+			"isb	\n\t"
+			"dsb	"
+			: : "r" (0x400) );
+		}
+
+		/*
+		 * We need to disable and flush the whole (L1 and L2) cache.
+		 * Let's do it in the safest possible way i.e. with
+		 * no memory access within the following sequence
+		 * including the stack.
+		 */
+		asm volatile(
+		"mrc	p15, 0, r0, c1, c0, 0	@ get CR \n\t"
+		"bic	r0, r0, #"__stringify(CR_C)" \n\t"
+		"mcr	p15, 0, r0, c1, c0, 0	@ set CR \n\t"
+		"isb	\n\t"
+		"bl	v7_flush_dcache_all \n\t"
+		"clrex	\n\t"
+		"mrc	p15, 0, r0, c1, c0, 1	@ get AUXCR \n\t"
+		"bic	r0, r0, #(1 << 6)	@ disable local coherency \n\t"
+		"mcr	p15, 0, r0, c1, c0, 1	@ set AUXCR \n\t"
+		"isb	\n\t"
+		"dsb	"
+		: : : "r0","r1","r2","r3","r4","r5","r6","r7",
+		      "r9","r10","r11","lr","memory");
+
+		cci_disable_port_by_cpu(mpidr);
+
+		__mcpm_outbound_leave_critical(cluster, CLUSTER_DOWN);
+	} else {
+		/*
+		 * If last man then undo any setup done previously.
+		 */
+		if (last_man) {
+			ve_spc_powerdown(cluster, false);
+			ve_spc_global_wakeup_irq(false);
+		}
+
+		arch_spin_unlock(&tc2_pm_lock);
+
+		/*
+		 * We need to disable and flush only the L1 cache.
+		 * Let's do it in the safest possible way as above.
+		 */
+		asm volatile(
+		"mrc	p15, 0, r0, c1, c0, 0	@ get CR \n\t"
+		"bic	r0, r0, #"__stringify(CR_C)" \n\t"
+		"mcr	p15, 0, r0, c1, c0, 0	@ set CR \n\t"
+		"isb	\n\t"
+		"bl	v7_flush_dcache_louis \n\t"
+		"clrex	\n\t"
+		"mrc	p15, 0, r0, c1, c0, 1	@ get AUXCR \n\t"
+		"bic	r0, r0, #(1 << 6)	@ disable local coherency \n\t"
+		"mcr	p15, 0, r0, c1, c0, 1	@ set AUXCR \n\t"
+		"isb	\n\t"
+		"dsb	"
+		: : : "r0","r1","r2","r3","r4","r5","r6","r7",
+		      "r9","r10","r11","lr","memory");
+	}
+
+	__mcpm_cpu_down(cpu, cluster);
+
+	/* Now we are prepared for power-down, do it: */
+	if (!skip_wfi)
+		wfi();
+
+	/* Not dead at this point?  Let our caller cope. */
+}
+
+static void tc2_pm_powered_up(void)
+{
+	unsigned int mpidr, cpu, cluster;
+	unsigned long flags;
+
+	mpidr = read_cpuid_mpidr();
+	cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
+	cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
+
+	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
+	BUG_ON(cluster >= TC2_CLUSTERS || cpu >= TC2_MAX_CPUS_PER_CLUSTER);
+
+	local_irq_save(flags);
+	arch_spin_lock(&tc2_pm_lock);
+
+	if (tc2_cluster_unused(cluster)) {
+		ve_spc_powerdown(cluster, false);
+		ve_spc_global_wakeup_irq(false);
+	}
+
+	if (!tc2_pm_use_count[cpu][cluster])
+		tc2_pm_use_count[cpu][cluster] = 1;
+
+	ve_spc_cpu_wakeup_irq(cluster, cpu, false);
+	ve_spc_set_resume_addr(cluster, cpu, 0);
+
+	arch_spin_unlock(&tc2_pm_lock);
+	local_irq_restore(flags);
+}
+
+static const struct mcpm_platform_ops tc2_pm_power_ops = {
+	.power_up	= tc2_pm_power_up,
+	.power_down	= tc2_pm_power_down,
+	.powered_up	= tc2_pm_powered_up,
+};
+
+static bool __init tc2_pm_usage_count_init(void)
+{
+	unsigned int mpidr, cpu, cluster;
+
+	mpidr = read_cpuid_mpidr();
+	cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
+	cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
+
+	pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
+	if (cluster >= TC2_CLUSTERS || cpu >= tc2_nr_cpus[cluster]) {
+		pr_err("%s: boot CPU is out of bound!\n", __func__);
+		return false;
+	}
+	tc2_pm_use_count[cpu][cluster] = 1;
+	return true;
+}
+
+/*
+ * Enable cluster-level coherency, in preparation for turning on the MMU.
+ */
+static void __naked tc2_pm_power_up_setup(unsigned int affinity_level)
+{
+	asm volatile (" \n"
+"	cmp	r0, #1 \n"
+"	bxne	lr \n"
+"	b	cci_enable_port_for_self ");
+}
+
+static int __init tc2_pm_init(void)
+{
+	int ret;
+	void __iomem *scc;
+	u32 a15_cluster_id, a7_cluster_id, sys_info;
+	struct device_node *np;
+
+	/*
+	 * The power management-related features are hidden behind
+	 * SCC registers. We need to extract runtime information like
+	 * cluster ids and number of CPUs really available in clusters.
+	 */
+	np = of_find_compatible_node(NULL, NULL,
+			"arm,vexpress-scc,v2p-ca15_a7");
+	scc = of_iomap(np, 0);
+	if (!scc)
+		return -ENODEV;
+
+	a15_cluster_id = readl_relaxed(scc + A15_CONF) & 0xf;
+	a7_cluster_id = readl_relaxed(scc + A7_CONF) & 0xf;
+	if (a15_cluster_id >= TC2_CLUSTERS || a7_cluster_id >= TC2_CLUSTERS)
+		return -EINVAL;
+
+	sys_info = readl_relaxed(scc + SYS_INFO);
+	tc2_nr_cpus[a15_cluster_id] = (sys_info >> 16) & 0xf;
+	tc2_nr_cpus[a7_cluster_id] = (sys_info >> 20) & 0xf;
+
+	/*
+	 * A subset of the SCC registers is also used to communicate
+	 * with the SPC (power controller). We need to be able to
+	 * drive it very early in the boot process to power up
+	 * processors, so we initialize the SPC driver here.
+	 */
+	ret = ve_spc_init(scc + SPC_BASE, a15_cluster_id);
+	if (ret)
+		return ret;
+
+	if (!cci_probed())
+		return -ENODEV;
+
+	if (!tc2_pm_usage_count_init())
+		return -EINVAL;
+
+	ret = mcpm_platform_register(&tc2_pm_power_ops);
+	if (!ret) {
+		mcpm_sync_init(tc2_pm_power_up_setup);
+		pr_info("TC2 power management initialized\n");
+	}
+	return ret;
+}
+
+early_initcall(tc2_pm_init);