Re: [PATCH v3 3/4] ARM: EXYNOS: add Exynos Dual Cluster Support
From: Tarek Dakhran
Date: Mon Nov 11 2013 - 03:13:59 EST
On 07.11.2013 17:01, Dave Martin wrote:
On Thu, Nov 07, 2013 at 08:12:48AM +0000, Vyacheslav Tyrtov wrote:
From: Tarek Dakhran <t.dakhran@xxxxxxxxxxx>
Add EDCS(Exynos Dual Cluster Support) for Samsung Exynos5410 SoC.
This enables all 8 cores, 4 x A7 and 4 x A15 run at the same time.
Signed-off-by: Tarek Dakhran <t.dakhran@xxxxxxxxxxx>
Signed-off-by: Vyacheslav Tyrtov <v.tyrtov@xxxxxxxxxxx>
---
arch/arm/mach-exynos/Makefile | 2 +
arch/arm/mach-exynos/edcs.c | 278 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 280 insertions(+)
create mode 100644 arch/arm/mach-exynos/edcs.c
diff --git a/arch/arm/mach-exynos/Makefile b/arch/arm/mach-exynos/Makefile
index 5369615..ba6efdb 100644
--- a/arch/arm/mach-exynos/Makefile
+++ b/arch/arm/mach-exynos/Makefile
@@ -34,3 +34,5 @@ AFLAGS_exynos-smc.o :=-Wa,-march=armv7-a$(plus_sec)
obj-$(CONFIG_MACH_EXYNOS4_DT) += mach-exynos4-dt.o
obj-$(CONFIG_MACH_EXYNOS5_DT) += mach-exynos5-dt.o
+
+obj-$(CONFIG_SOC_EXYNOS5410) += edcs.o
diff --git a/arch/arm/mach-exynos/edcs.c b/arch/arm/mach-exynos/edcs.c
new file mode 100644
index 0000000..980bfdd
--- /dev/null
+++ b/arch/arm/mach-exynos/edcs.c
@@ -0,0 +1,278 @@
+/*
+ * arch/arm/mach-exynos/edcs.c - exynos dual cluster power management support
+ *
+ * Copyright (c) 2013 Samsung Electronics Co., Ltd.
+ * Author: Tarek Dakhran <t.dakhran@xxxxxxxxxxx>
+ *
+ * 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.
+ *
+ * EDCS(exynos dual cluster support) for Exynos5410 SoC.
+ */
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/of_address.h>
+#include <linux/spinlock.h>
+#include <linux/errno.h>
+#include <linux/irqchip/arm-gic.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 <mach/regs-pmu.h>
+
+#define EDCS_CPUS_PER_CLUSTER 4
+#define EDCS_CLUSTERS 2
+
+/* Exynos5410 power management registers */
+#define EDCS_CORE_CONFIGURATION(_nr) (S5P_ARM_CORE0_CONFIGURATION \
+ + ((_nr) * 0x80))
+#define EDCS_CORE_STATUS(_nr) (EDCS_CORE_CONFIGURATION(_nr) + 0x4)
+#define EDCS_CORE_OPTION(_nr) (EDCS_CORE_CONFIGURATION(_nr) + 0x8)
+
+#define REG_CPU_STATE_ADDR0 (S5P_VA_SYSRAM_NS + 0x28)
+#define REG_CPU_STATE_ADDR(_nr) (REG_CPU_STATE_ADDR0 + \
+ (_nr) * EDCS_CPUS_PER_CLUSTER)
+
+#define SECONDARY_RESET (1 << 1)
+#define REG_ENTRY_ADDR (S5P_VA_SYSRAM_NS + 0x1c)
+
+static arch_spinlock_t edcs_lock = __ARCH_SPIN_LOCK_UNLOCKED;
+
+static int edcs_use_count[EDCS_CPUS_PER_CLUSTER][EDCS_CLUSTERS];
+static int core_count[EDCS_CLUSTERS];
+
+static void exynos_core_power_control(unsigned int cpu, unsigned int cluster,
+ bool enable)
+{
+ unsigned int offset = cluster * MAX_CPUS_PER_CLUSTER + cpu;
+ int value = enable ? S5P_CORE_LOCAL_PWR_EN : 0;
+
+ if ((readl_relaxed(EDCS_CORE_STATUS(offset)) & 0x3) != value) {
I wonder if there is a race here.
If there is a pending powerdown which has reached the __mcpm_cpu_down()
stage, then the kernel has no way to know what is still pending. This
means that when calling exynos_power_up(cpu, cluster) after a successful
call to exynos_power_down(same cpu, cluster), there is a chance that
the CPU still gets powered down, because of the pending
exynos_core_power_control() on the outbound side.
This isn't an issue for TC2, because TC2's power controller queues
requests and services them in order, so a new powerup request cannot
race with a powerdown request in that way.
For exynos5410, it looks like the kernel needs to do that sequencing,
based on my guess about what the EDCS_CORE_STATUS() bits tell us.
I think that for correct behaviour we would need to wait for the race to
be resolved here, but only if a powerdown might be pending.
This implies that something like a call to the power_down_finish()
method (which you would need to write -- see my comments below) is
needed in exynos_core_power_up().
It might make sense to have a per-cpu flag that tracks whether a
powerdown is pending. The flag could be set after
__mcpm_cpu_going_down() is called, and cleared in the powered_up()
method (which you would need to add).
Maybe we should always just poll and wait, though. exynos_power_up()
should never be called for a CPU that the kernel thinks is already up,
so it should either be down already (in which case we will poll the
status once and then continue), or a power down is pending (in which
case we must wait, but we know the wait will terminate). This would
be simpler than tracking a "power down pending" flag for each CPU.
+ wmb();
+ writel_relaxed(value, EDCS_CORE_CONFIGURATION(offset));
+ }
+}
+
+static void exynos_core_power_up(unsigned int cpu, unsigned int cluster)
+{
+ exynos_core_power_control(cpu, cluster, true);
+}
+
+static void exynos_core_power_down(unsigned int cpu, unsigned int cluster)
+{
+ exynos_core_power_control(cpu, cluster, false);
+}
+
+void set_boot_flag(unsigned int cpu, unsigned int mode)
+{
+ writel_relaxed(mode, REG_CPU_STATE_ADDR(cpu));
+}
+
+static int exynos_power_up(unsigned int cpu, unsigned int cluster)
+{
+ pr_debug("%s: cpu %u cluster %u\n", __func__, cpu, cluster);
+ BUG_ON(cpu >= EDCS_CPUS_PER_CLUSTER || cluster >= EDCS_CLUSTERS);
+
+ local_irq_disable();
+ arch_spin_lock(&edcs_lock);
+
+ edcs_use_count[cpu][cluster]++;
+ if (edcs_use_count[cpu][cluster] == 1) {
+ ++core_count[cluster];
+ set_boot_flag(cpu, SECONDARY_RESET);
+ exynos_core_power_up(cpu, cluster);
+ } else if (edcs_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(&edcs_lock);
+ local_irq_enable();
+
+ return 0;
+}
+static void exynos_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: CORE%d on CLUSTER %d\n", __func__, cpu, cluster);
+ BUG_ON(cpu >= EDCS_CPUS_PER_CLUSTER || cluster >= EDCS_CLUSTERS);
+
+ __mcpm_cpu_going_down(cpu, cluster);
+
+ arch_spin_lock(&edcs_lock);
+ BUG_ON(__mcpm_cluster_state(cluster) != CLUSTER_UP);
+ edcs_use_count[cpu][cluster]--;
+ if (edcs_use_count[cpu][cluster] == 0) {
+ --core_count[cluster];
+ if (core_count[cluster] == 0)
+ last_man = true;
+ } else if (edcs_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 (!skip_wfi)
+ gic_cpu_if_down();
+
+ if (last_man && __mcpm_outbound_enter_critical(cpu, cluster)) {
+ arch_spin_unlock(&edcs_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.
+ *
+ * Note: fp is preserved to the stack explicitly prior doing
+ * this since adding it to the clobber list is incompatible
+ * with having CONFIG_FRAME_POINTER=y.
+ */
+ asm volatile(
+ "str fp, [sp, #-4]!\n\t"
+ "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\n\t"
+ "ldr fp, [sp], #4"
The v7_exit_coherency_flush() macro is now in linux-next, so
you can now use it to replace these sequences.
This can be replaced by v7_exit_coherency_flush(all).
+ : : : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
+ "r9", "r10", "lr", "memory");
+
+ cci_disable_port_by_cpu(mpidr);
+
+ __mcpm_outbound_leave_critical(cluster, CLUSTER_DOWN);
+
+ } else {
+ arch_spin_unlock(&edcs_lock);
+ /*
+ * We need to disable and flush only the L1 cache.
+ * Let's do it in the safest possible way as above.
+ */
+ asm volatile(
+ "str fp, [sp, #-4]!\n\t"
+ "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\n\t"
+ "ldr fp, [sp], #4"
v7_exit_coherency_flush(louis) should work here.
arch/arm/mach-vexpress/tc2_pm.c (in linux-next) shows how to use it.
+ : : : "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
+ "r9", "r10", "lr", "memory");
+
+ }
+ __mcpm_cpu_down(cpu, cluster);
+
+ if (!skip_wfi) {
+ exynos_core_power_down(cpu, cluster);
+ wfi();
+ }
+}
+
+static const struct mcpm_platform_ops exynos_power_ops = {
+ .power_up = exynos_power_up,
+ .power_down = exynos_power_down,
+};
The new mcpm_power_down_finish() call is also present in linux-next now,
so it should get merged into v3.13.
One effect of this is that you should provide a power_down_finish()
method in your mcpm_platform_ops, to provide the kernel with a way to
check that a CPU has finished powering down. This would usually involve
checking some status bits in the power controller. See the comments for
mcpm_power_down_finish() in arch/arm/include/asm/mcpm.h for details.
No platform backend for power_down_finish() is merged yet. The most
recent patch for TC2 was posted here -- I need to follow up on it.
http://lists.infradead.org/pipermail/linux-arm-kernel/2013-October/201619.html
[PATCH v3 3/3] ARM: vexpress/TC2: Implement MCPM power_down_finish()
This may look quite different for exynos5410.
Cheers
---Dave
Thanks Dave.
I'm working on this problem.
Best regards,
Tarek Dakhran.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/