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[PATCH V10 12/13] MIPS: Loongson 3: Add CPU hotplug support

To: Ralf Baechle <ralf@linux-mips.org>
Subject: [PATCH V10 12/13] MIPS: Loongson 3: Add CPU hotplug support
From: Huacai Chen <chenhc@lemote.com>
Date: Mon, 15 Apr 2013 20:47:07 +0800
Cc: John Crispin <john@phrozen.org>, linux-mips@linux-mips.org, Fuxin Zhang <zhangfx@lemote.com>, Zhangjin Wu <wuzhangjin@gmail.com>, Huacai Chen <chenhc@lemote.com>, Hongliang Tao <taohl@lemote.com>, Hua Yan <yanh@lemote.com>
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Tips of Loongson's CPU hotplug:
1, To fully shutdown a core in Loongson 3, the target core should go to
   CKSEG1 and flush all L1 cache entries at first. Then, another core
   (usually Core 0) can safely disable the clock of the target core. So
   play_dead() call loongson3_play_dead() via CKSEG1 (both uncached and
   unmmaped).
2, The default clocksource of Loongson is MIPS. Since clock source is a
   global device, timekeeping need the CP0' Count registers of each core
   be synchronous. Thus, when a core is up, we use a SMP_ASK_C0COUNT IPI
   to ask Core-0's Count.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Hongliang Tao <taohl@lemote.com>
Signed-off-by: Hua Yan <yanh@lemote.com>
---
 arch/mips/Kconfig                              |    1 +
 arch/mips/include/asm/mach-loongson/loongson.h |    6 +-
 arch/mips/include/asm/smp.h                    |    1 +
 arch/mips/loongson/loongson-3/irq.c            |   10 ++
 arch/mips/loongson/loongson-3/smp.c            |  176 +++++++++++++++++++++++-
 5 files changed, 189 insertions(+), 5 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index da0bad2..7fe8a4e 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -272,6 +272,7 @@ config LASAT
 config MACH_LOONGSON
        bool "Loongson family of machines"
        select SYS_SUPPORTS_ZBOOT
+       select SYS_SUPPORTS_HOTPLUG_CPU
        help
          This enables the support of Loongson family of machines.
 
diff --git a/arch/mips/include/asm/mach-loongson/loongson.h 
b/arch/mips/include/asm/mach-loongson/loongson.h
index 40b4892..d4bae71 100644
--- a/arch/mips/include/asm/mach-loongson/loongson.h
+++ b/arch/mips/include/asm/mach-loongson/loongson.h
@@ -247,6 +247,9 @@ static inline void do_perfcnt_IRQ(void)
 #define LOONGSON_PXARB_CFG             LOONGSON_REG(LOONGSON_REGBASE + 0x68)
 #define LOONGSON_PXARB_STATUS          LOONGSON_REG(LOONGSON_REGBASE + 0x6c)
 
+/* Chip Config */
+#define LOONGSON_CHIPCFG0              LOONGSON_REG(LOONGSON_REGBASE + 0x80)
+
 /* pcimap */
 
 #define LOONGSON_PCIMAP_PCIMAP_LO0     0x0000003f
@@ -262,9 +265,6 @@ static inline void do_perfcnt_IRQ(void)
 #ifdef CONFIG_CPU_SUPPORTS_CPUFREQ
 #include <linux/cpufreq.h>
 extern struct cpufreq_frequency_table loongson2_clockmod_table[];
-
-/* Chip Config */
-#define LOONGSON_CHIPCFG0              LOONGSON_REG(LOONGSON_REGBASE + 0x80)
 #endif
 
 /*
diff --git a/arch/mips/include/asm/smp.h b/arch/mips/include/asm/smp.h
index eb60087..efa02ac 100644
--- a/arch/mips/include/asm/smp.h
+++ b/arch/mips/include/asm/smp.h
@@ -42,6 +42,7 @@ extern int __cpu_logical_map[NR_CPUS];
 #define SMP_ICACHE_FLUSH       0x4
 /* Used by kexec crashdump to save all cpu's state */
 #define SMP_DUMP               0x8
+#define SMP_ASK_C0COUNT                0x10
 
 extern volatile cpumask_t cpu_callin_map;
 
diff --git a/arch/mips/loongson/loongson-3/irq.c 
b/arch/mips/loongson/loongson-3/irq.c
index 27aef31..83f84e6 100644
--- a/arch/mips/loongson/loongson-3/irq.c
+++ b/arch/mips/loongson/loongson-3/irq.c
@@ -85,3 +85,13 @@ void __init mach_init_irq(void)
 
        set_c0_status(STATUSF_IP2 | STATUSF_IP6);
 }
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+void fixup_irqs(void)
+{
+       irq_cpu_offline();
+       clear_c0_status(ST0_IM);
+}
+
+#endif
diff --git a/arch/mips/loongson/loongson-3/smp.c 
b/arch/mips/loongson/loongson-3/smp.c
index cb996d5..a402e3d 100644
--- a/arch/mips/loongson/loongson-3/smp.c
+++ b/arch/mips/loongson/loongson-3/smp.c
@@ -30,6 +30,9 @@
 
 #include "smp.h"
 
+DEFINE_PER_CPU(int, cpu_state);
+DEFINE_PER_CPU(uint32_t, core0_c0count);
+
 /* read a 64bit value from ipi register */
 uint64_t loongson3_ipi_read64(void * addr)
 {
@@ -169,8 +172,8 @@ static void loongson3_send_ipi_mask(const struct cpumask 
*mask, unsigned int act
 
 void loongson3_ipi_interrupt(struct pt_regs *regs)
 {
-       int cpu = smp_processor_id();
-       unsigned int action;
+       int i, cpu = smp_processor_id();
+       unsigned int action, c0count;
 
        /* Load the ipi register to figure out what we're supposed to do */
        action = loongson3_ipi_read32(ipi_status0_regs[cpu]);
@@ -185,14 +188,24 @@ void loongson3_ipi_interrupt(struct pt_regs *regs)
        if (action & SMP_CALL_FUNCTION) {
                smp_call_function_interrupt();
        }
+
+       if (action & SMP_ASK_C0COUNT) {
+               BUG_ON(cpu != 0);
+               c0count = read_c0_count();
+               for (i=1; i < nr_cpus_loongson; i++)
+                       per_cpu(core0_c0count, i) = c0count;
+       }
 }
 
+#define MAX_LOOPS 1200
 /*
  * SMP init and finish on secondary CPUs
  */
 void __cpuinit loongson3_init_secondary(void)
 {
        int i;
+       uint32_t initcount;
+       unsigned int cpu = smp_processor_id();
        unsigned int imask = STATUSF_IP7 | STATUSF_IP6 |
                             STATUSF_IP3 | STATUSF_IP2;
 
@@ -202,6 +215,19 @@ void __cpuinit loongson3_init_secondary(void)
        for (i = 0; i < nr_cpus_loongson; i++) {
                loongson3_ipi_write32(0xffffffff, ipi_en0_regs[i]);
        }
+
+       per_cpu(cpu_state, cpu) = CPU_ONLINE;
+
+       i = 0;
+       __get_cpu_var(core0_c0count) = 0;
+       loongson3_send_ipi_single(0, SMP_ASK_C0COUNT);
+       while (!__get_cpu_var(core0_c0count))
+               i++;
+
+       if (i > MAX_LOOPS)
+               i = MAX_LOOPS;
+       initcount = __get_cpu_var(core0_c0count) + i;
+       write_c0_count(initcount);
 }
 
 void __cpuinit loongson3_smp_finish(void)
@@ -235,6 +261,8 @@ void __init loongson3_smp_setup(void)
 
 void __init loongson3_prepare_cpus(unsigned int max_cpus)
 {
+       init_cpu_present(cpu_possible_mask);
+       per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
 }
 
 /*
@@ -268,6 +296,146 @@ void __init loongson3_cpus_done(void)
 {
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+
+extern void fixup_irqs(void);
+extern void (*flush_cache_all)(void);
+
+static int loongson3_cpu_disable(void)
+{
+       unsigned long flags;
+       unsigned int cpu = smp_processor_id();
+
+       if (cpu == 0)
+               return -EBUSY;
+
+       set_cpu_online(cpu, false);
+       cpu_clear(cpu, cpu_callin_map);
+       local_irq_save(flags);
+       fixup_irqs();
+       local_irq_restore(flags);
+       flush_cache_all();
+       local_flush_tlb_all();
+
+       return 0;
+}
+
+
+static void loongson3_cpu_die(unsigned int cpu)
+{
+       while (per_cpu(cpu_state, cpu) != CPU_DEAD)
+               cpu_relax();
+
+       mb();
+}
+
+/* To shutdown a core in Loongson 3, the target core should go to CKSEG1 and
+ * flush all L1 entries at first. Then, another core (usually Core 0) can
+ * safely disable the clock of the target core. loongson3_play_dead() is
+ * called via CKSEG1 (uncached and unmmaped) */
+void loongson3_play_dead(int *state_addr)
+{
+       __asm__ __volatile__(
+               "      .set push                         \n"
+               "      .set noreorder                    \n"
+               "      li $t0, 0x80000000                \n" /* KSEG0 */
+               "      li $t1, 512                       \n" /* num of L1 
entries */
+               "flush_loop:                             \n" /* flush L1 */
+               "      cache 0, 0($t0)                   \n" /* ICache */
+               "      cache 0, 1($t0)                   \n"
+               "      cache 0, 2($t0)                   \n"
+               "      cache 0, 3($t0)                   \n"
+               "      cache 1, 0($t0)                   \n" /* DCache */
+               "      cache 1, 1($t0)                   \n"
+               "      cache 1, 2($t0)                   \n"
+               "      cache 1, 3($t0)                   \n"
+               "      addiu $t0, $t0, 0x20              \n"
+               "      bnez  $t1, flush_loop             \n"
+               "      addiu $t1, $t1, -1                \n"
+               "      li    $t0, 0x7                    \n" /* *state_addr = 
CPU_DEAD; */
+               "      sw    $t0, 0($a0)                 \n"
+               "      sync                              \n"
+               "      cache 21, 0($a0)                  \n" /* flush entry of 
*state_addr */
+               "      .set pop                          \n");
+
+       __asm__ __volatile__(
+               "      .set push                         \n"
+               "      .set noreorder                    \n"
+               "      .set mips64                       \n"
+               "      mfc0  $t2, $15, 1                 \n"
+               "      andi  $t2, 0x3ff                  \n"
+               "      .set mips3                        \n"
+               "      dli   $t0, 0x900000003ff01000     \n"
+               "      andi  $t3, $t2, 0x3               \n"
+               "      sll   $t3, 8                      \n"  /* get cpu id */
+               "      or    $t0, $t0, $t3               \n"
+               "      andi  $t1, $t2, 0xc               \n"
+               "      dsll  $t1, 42                     \n"  /* get node id */
+               "      or    $t0, $t0, $t1               \n"
+               "wait_for_init:                          \n"
+               "      li    $a0, 0x100                  \n"
+               "idle_loop:                              \n"
+               "      bnez  $a0, idle_loop              \n"
+               "      addiu $a0, -1                     \n"
+               "      lw    $v0, 0x20($t0)              \n"  /* get PC via 
mailbox */
+               "      nop                               \n"
+               "      beqz  $v0, wait_for_init          \n"
+               "      nop                               \n"
+               "      ld    $sp, 0x28($t0)              \n"  /* get SP via 
mailbox */
+               "      nop                               \n"
+               "      ld    $gp, 0x30($t0)              \n"  /* get GP via 
mailbox */
+               "      nop                               \n"
+               "      ld    $a1, 0x38($t0)              \n"
+               "      nop                               \n"
+               "      jr  $v0                           \n"  /* jump to 
initial PC */
+               "      nop                               \n"
+               "      .set pop                          \n");
+}
+
+void play_dead(void)
+{
+       int *state_addr;
+       unsigned int cpu = smp_processor_id();
+       void (*play_dead_at_ckseg1)(int *);
+
+       idle_task_exit();
+       play_dead_at_ckseg1 = (void *)CKSEG1ADDR((unsigned 
long)loongson3_play_dead);
+       state_addr = &per_cpu(cpu_state, cpu);
+       mb();
+       play_dead_at_ckseg1(state_addr);
+}
+
+#define CPU_POST_DEAD_FROZEN   (CPU_POST_DEAD | CPU_TASKS_FROZEN)
+static int __cpuinit loongson3_cpu_callback(struct notifier_block *nfb,
+       unsigned long action, void *hcpu)
+{
+       unsigned int cpu = (unsigned long)hcpu;
+
+       switch (action) {
+       case CPU_POST_DEAD:
+       case CPU_POST_DEAD_FROZEN:
+               printk(KERN_INFO "Disable clock for CPU#%d\n", cpu);
+               LOONGSON_CHIPCFG0 &= ~(1 << (12 + cpu));
+               break;
+       case CPU_UP_PREPARE:
+       case CPU_UP_PREPARE_FROZEN:
+               printk(KERN_INFO "Enable clock for CPU#%d\n", cpu);
+               LOONGSON_CHIPCFG0 |= 1 << (12 + cpu);
+               break;
+       }
+
+       return NOTIFY_OK;
+}
+
+static int __cpuinit register_loongson3_notifier(void)
+{
+       hotcpu_notifier(loongson3_cpu_callback, 0);
+       return 0;
+}
+early_initcall(register_loongson3_notifier);
+
+#endif
+
 struct plat_smp_ops loongson3_smp_ops = {
        .send_ipi_single = loongson3_send_ipi_single,
        .send_ipi_mask = loongson3_send_ipi_mask,
@@ -277,4 +445,8 @@ struct plat_smp_ops loongson3_smp_ops = {
        .boot_secondary = loongson3_boot_secondary,
        .smp_setup = loongson3_smp_setup,
        .prepare_cpus = loongson3_prepare_cpus,
+#ifdef CONFIG_HOTPLUG_CPU
+       .cpu_disable = loongson3_cpu_disable,
+       .cpu_die = loongson3_cpu_die,
+#endif
 };
-- 
1.7.7.3


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