ARM: vexpress: introduce DCSCB support

This adds basic CPU and cluster reset controls on RTSM for the
A15x4-A7x4 model configuration using the Dual Cluster System
Configuration Block (DCSCB).

The cache coherency interconnect (CCI) is not handled yet.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Pawel Moll <pawel.moll@arm.com>

3 files changed, 173 insertions, 0 deletions

diff --git a/arch/arm/mach-vexpress/Kconfig b/arch/arm/mach-vexpress/Kconfig
index 5907e10c37fd..2f46385c2819 100644
--- a/arch/arm/mach-vexpress/Kconfig
+++ b/arch/arm/mach-vexpress/Kconfig
@@ -57,4 +57,12 @@ config ARCH_VEXPRESS_CORTEX_A5_A9_ERRATA
 config ARCH_VEXPRESS_CA9X4
         bool "Versatile Express Cortex-A9x4 tile"
 
+config ARCH_VEXPRESS_DCSCB
+        bool "Dual Cluster System Control Block (DCSCB) support"
+        depends on MCPM
+        help
+          Support for the Dual Cluster System Configuration Block (DCSCB).
+          This is needed to provide CPU and cluster power management
+          on RTSM implementing big.LITTLE.
+
 endmenu
diff --git a/arch/arm/mach-vexpress/Makefile b/arch/arm/mach-vexpress/Makefile
index 42703e8b4d3b..518519f57a5e 100644
--- a/arch/arm/mach-vexpress/Makefile
+++ b/arch/arm/mach-vexpress/Makefile
@@ -6,5 +6,6 @@ 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
 obj-$(CONFIG_SMP)                       += platsmp.o
 obj-$(CONFIG_HOTPLUG_CPU)               += hotplug.o
diff --git a/arch/arm/mach-vexpress/dcscb.c b/arch/arm/mach-vexpress/dcscb.c
new file mode 100644
index 000000000000..2ca4bbce530c
--- /dev/null
+++ b/arch/arm/mach-vexpress/dcscb.c
@@ -0,0 +1,164 @@
+/*
+ * arch/arm/mach-vexpress/dcscb.c - Dual Cluster System Configuration Block
+ *
+ * Created by:  Nicolas Pitre, May 2012
+ * Copyright:   (C) 2012-2013  Linaro 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/kernel.h>
+#include <linux/io.h>
+#include <linux/spinlock.h>
+#include <linux/errno.h>
+#include <linux/of_address.h>
+#include <linux/vexpress.h>
+
+#include <asm/mcpm.h>
+#include <asm/proc-fns.h>
+#include <asm/cacheflush.h>
+#include <asm/cputype.h>
+#include <asm/cp15.h>
+
+
+#define RST_HOLD0       0x0
+#define RST_HOLD1       0x4
+#define SYS_SWRESET     0x8
+#define RST_STAT0       0xc
+#define RST_STAT1       0x10
+#define EAG_CFG_R       0x20
+#define EAG_CFG_W       0x24
+#define KFC_CFG_R       0x28
+#define KFC_CFG_W       0x2c
+#define DCS_CFG_R       0x30
+
+/*
+ * We can't use regular spinlocks. In the switcher case, it is possible
+ * for an outbound CPU to call power_down() while its inbound counterpart
+ * is already live using the same logical CPU number which trips lockdep
+ * debugging.
+ */
+static arch_spinlock_t dcscb_lock = __ARCH_SPIN_LOCK_UNLOCKED;
+
+static void __iomem *dcscb_base;
+
+static int dcscb_power_up(unsigned int cpu, unsigned int cluster)
+{
+        unsigned int rst_hold, cpumask = (1 << cpu);
+
+        pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
+        if (cpu >= 4 || cluster >= 2)
+                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(&dcscb_lock);
+
+        rst_hold = readl_relaxed(dcscb_base + RST_HOLD0 + cluster * 4);
+        if (rst_hold & (1 << 8)) {
+                /* remove cluster reset and add individual CPU's reset */
+                rst_hold &= ~(1 << 8);
+                rst_hold |= 0xf;
+        }
+        rst_hold &= ~(cpumask | (cpumask << 4));
+        writel_relaxed(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4);
+
+        arch_spin_unlock(&dcscb_lock);
+        local_irq_enable();
+
+        return 0;
+}
+
+static void dcscb_power_down(void)
+{
+        unsigned int mpidr, cpu, cluster, rst_hold, cpumask, last_man;
+
+        mpidr = read_cpuid_mpidr();
+        cpu = MPIDR_AFFINITY_LEVEL(mpidr, 0);
+        cluster = MPIDR_AFFINITY_LEVEL(mpidr, 1);
+        cpumask = (1 << cpu);
+
+        pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
+        BUG_ON(cpu >= 4 || cluster >= 2);
+
+        arch_spin_lock(&dcscb_lock);
+        rst_hold = readl_relaxed(dcscb_base + RST_HOLD0 + cluster * 4);
+        rst_hold |= cpumask;
+        if (((rst_hold | (rst_hold >> 4)) & 0xf) == 0xf)
+                rst_hold |= (1 << 8);
+        writel_relaxed(rst_hold, dcscb_base + RST_HOLD0 + cluster * 4);
+        arch_spin_unlock(&dcscb_lock);
+        last_man = (rst_hold & (1 << 8));
+
+        /*
+         * Now let's clean our L1 cache and shut ourself down.
+         * If we're the last CPU in this cluster then clean L2 too.
+         */
+
+        /*
+         * A15/A7 can hit in the cache with SCTLR.C=0, so we don't need
+         * a preliminary flush here for those CPUs.  At least, that's
+         * the theory -- without the extra flush, Linux explodes on
+         * RTSM (to be investigated)..
+         */
+        flush_cache_louis();
+        set_cr(get_cr() & ~CR_C);
+
+        if (!last_man) {
+                flush_cache_louis();
+        } else {
+                flush_cache_all();
+                outer_flush_all();
+        }
+
+        /* Disable local coherency by clearing the ACTLR "SMP" bit: */
+        set_auxcr(get_auxcr() & ~(1 << 6));
+
+        /* Now we are prepared for power-down, do it: */
+        dsb();
+        wfi();
+
+        /* Not dead at this point?  Let our caller cope. */
+}
+
+static const struct mcpm_platform_ops dcscb_power_ops = {
+        .power_up       = dcscb_power_up,
+        .power_down     = dcscb_power_down,
+};
+
+static int __init dcscb_init(void)
+{
+        struct device_node *node;
+        int ret;
+
+        node = of_find_compatible_node(NULL, NULL, "arm,rtsm,dcscb");
+        if (!node)
+                return -ENODEV;
+        dcscb_base = of_iomap(node, 0);
+        if (!dcscb_base)
+                return -EADDRNOTAVAIL;
+
+        ret = mcpm_platform_register(&dcscb_power_ops);
+        if (ret) {
+                iounmap(dcscb_base);
+                return ret;
+        }
+
+        pr_info("VExpress DCSCB support installed\n");
+
+        /*
+         * Future entries into the kernel can now go
+         * through the cluster entry vectors.
+         */
+        vexpress_flags_set(virt_to_phys(mcpm_entry_point));
+
+        return 0;
+}
+
+early_initcall(dcscb_init);