On Wed, Jan 08, 2014 at 10:44:27AM +0800, Huacai Chen wrote:
> 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@xxxxxxxxxx>
> Signed-off-by: Hongliang Tao <taohl@xxxxxxxxxx>
> Signed-off-by: Hua Yan <yanh@xxxxxxxxxx>
> ---
> arch/mips/include/asm/mach-loongson/irq.h | 1 +
> arch/mips/include/asm/mach-loongson/loongson.h | 6 +-
> arch/mips/include/asm/smp.h | 1 +
> arch/mips/loongson/Kconfig | 1 +
> arch/mips/loongson/loongson-3/irq.c | 10 ++
> arch/mips/loongson/loongson-3/smp.c | 171 +++++++++++++++++++++++-
> 6 files changed, 185 insertions(+), 5 deletions(-)
>
> diff --git a/arch/mips/include/asm/mach-loongson/irq.h b/arch/mips/include/asm/mach-loongson/irq.h
> index d2f0e2a..620b3e9 100644
> --- a/arch/mips/include/asm/mach-loongson/irq.h
> +++ b/arch/mips/include/asm/mach-loongson/irq.h
> @@ -22,6 +22,7 @@
>
> #endif
>
> +extern void fixup_irqs(void);
> extern void loongson3_ipi_interrupt(struct pt_regs *regs);
>
> #include_next <irq.h>
> diff --git a/arch/mips/include/asm/mach-loongson/loongson.h b/arch/mips/include/asm/mach-loongson/loongson.h
> index f185907..f3fd1eb 100644
> --- a/arch/mips/include/asm/mach-loongson/loongson.h
> +++ b/arch/mips/include/asm/mach-loongson/loongson.h
> @@ -249,6 +249,9 @@ 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
> @@ -264,9 +267,6 @@ 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/Kconfig b/arch/mips/loongson/Kconfig
> index 4f3967c..f29e604 100644
> --- a/arch/mips/loongson/Kconfig
> +++ b/arch/mips/loongson/Kconfig
> @@ -77,6 +77,7 @@ config LEMOTE_MACH3A
> select SYS_HAS_CPU_LOONGSON3
> select SYS_HAS_EARLY_PRINTK
> select SYS_SUPPORTS_SMP
> + select SYS_SUPPORTS_HOTPLUG_CPU
> select SYS_SUPPORTS_64BIT_KERNEL
> select SYS_SUPPORTS_HIGHMEM
> select SYS_SUPPORTS_LITTLE_ENDIAN
> diff --git a/arch/mips/loongson/loongson-3/irq.c b/arch/mips/loongson/loongson-3/irq.c
> index d8920a8..d457366 100644
> --- a/arch/mips/loongson/loongson-3/irq.c
> +++ b/arch/mips/loongson/loongson-3/irq.c
> @@ -128,3 +128,13 @@ 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 a264bcb..059ef94 100644
> --- a/arch/mips/loongson/loongson-3/smp.c
> +++ b/arch/mips/loongson/loongson-3/smp.c
> @@ -26,10 +26,14 @@
> #include <asm/time.h>
> #include <asm/clock.h>
> #include <asm/tlbflush.h>
> +#include <asm/cacheflush.h>
> #include <loongson.h>
>
> #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)
> {
> @@ -170,8 +174,8 @@ loongson3_send_ipi_mask(const struct cpumask *mask, unsigned int action)
>
> 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]);
> @@ -184,14 +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 < loongson_sysconf.nr_cpus; i++)
> + per_cpu(core0_c0count, i) = c0count;
> + }
> }
>
> +#define MAX_LOOPS 1000
> /*
> * SMP init and finish on secondary CPUs
> */
> void 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;
>
> @@ -200,6 +214,21 @@ void loongson3_init_secondary(void)
>
> for (i = 0; i < loongson_sysconf.nr_cpus; 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++;
> + cpu_relax();
> + }
> +
> + if (i > MAX_LOOPS)
> + i = MAX_LOOPS;
> + initcount = __get_cpu_var(core0_c0count) + i;
> + write_c0_count(initcount);
> }
>
> void loongson3_smp_finish(void)
> @@ -234,6 +263,8 @@ 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;
> }
>
> /*
> @@ -267,6 +298,138 @@ void __init loongson3_cpus_done(void)
> {
> }
>
> +#ifdef CONFIG_HOTPLUG_CPU
> +
> +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)
Use static maybe?
> +{
> + __asm__ __volatile__(
> + " .set push \n"
> + " .set noreorder \n"
> + " li $t0, 0x80000000 \n" /* KSEG0 */
> + " move $t1, %0 \n" /* num of L1 entries */
> + "1: cache 0, 0($t0) \n" /* flush L1 ICache */
> + " cache 0, 1($t0) \n"
> + " cache 0, 2($t0) \n"
> + " cache 0, 3($t0) \n"
> + " cache 1, 0($t0) \n" /* flush L1 DCache */
> + " cache 1, 1($t0) \n"
> + " cache 1, 2($t0) \n"
> + " cache 1, 3($t0) \n"
> + " addiu $t0, $t0, 0x20 \n"
> + " bnez $t1, 1b \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"
> + : /* No Output */
> + : "r" (cpu_data[0].dcache.sets));
It looks better now that the cash size is not hardcoded. That said could
it be possible to use the corresponding cpu number instead of accessing
the value of cpu 0?
> +
> + __asm__ __volatile__(
> + " .set push \n"
> + " .set noreorder \n"
> + " .set mips64 \n"
> + " mfc0 $t2, $15, 1 \n"
> + " andi $t2, 0x3ff \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"
> + "1: li $a0, 0x100 \n" /* wait for init loop */
> + "2: bnez $a0, 2b \n" /* idle loop */
As you told me this loop is there to limit the mailbox access rate.
Maybe it should worth noting that in the comment instead of "idle loop".
> + " addiu $a0, -1 \n"
> + " lw $v0, 0x20($t0) \n" /* get PC via mailbox */
> + " beqz $v0, 1b \n"
> + " nop \n"
> + " ld $sp, 0x28($t0) \n" /* get SP via mailbox */
> + " ld $gp, 0x30($t0) \n" /* get GP via mailbox */
> + " ld $a1, 0x38($t0) \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 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:
> + pr_info("Disable clock for CPU#%d\n", cpu);
> + LOONGSON_CHIPCFG0 &= ~(1 << (12 + cpu));
> + break;
> + case CPU_UP_PREPARE:
> + case CPU_UP_PREPARE_FROZEN:
> + pr_info("Enable clock for CPU#%d\n", cpu);
> + LOONGSON_CHIPCFG0 |= 1 << (12 + cpu);
> + break;
> + }
> +
> + return NOTIFY_OK;
> +}
> +
> +static int 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,
> @@ -276,4 +439,8 @@ 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
>
>
--
Aurelien Jarno GPG: 1024D/F1BCDB73
aurelien@xxxxxxxxxxx http://www.aurel32.net
