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MIPS: smp-cps: hotplug support

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This patch adds support for offlining CPUs via hotplug when using the
CONFIG_MIPS_CPS SMP implementation. When a CPU is offlined one of 2
things will happen:

  - If the CPU is part of a core which implements the MT ASE and there
    is at least one other VPE online within that core then the VPE will
    be halted by settings its TCHalt bit.

  - Otherwise if supported the core will be powered down via the CPC.

  - Otherwise the CPU will hang by executing an infinite loop.

Bringing CPUs back online is then a process of either clearing the
appropriate VPEs TCHalt bit or powering up the appropriate core via the
CPC. Throughout the process the struct core_boot_config vpe_mask field
must be maintained such that mips_cps_boot_vpes will start & stop the
correct VPEs.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
This commit is contained in:
Paul Burton 2014-04-14 14:13:57 +01:00
parent 3179d37ee1
commit 1d8f1f5a78
2 changed files with 155 additions and 2 deletions
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2
arch/mips/Kconfig
View file

@ -2059,9 +2059,11 @@ config MIPS_CPS
depends on SYS_SUPPORTS_MIPS_CPS
select MIPS_CM
select MIPS_CPC
select MIPS_CPS_PM if HOTPLUG_CPU
select MIPS_GIC_IPI
select SMP
select SYNC_R4K if (CEVT_R4K || CSRC_R4K)
select SYS_SUPPORTS_HOTPLUG_CPU
select SYS_SUPPORTS_SMP
select WEAK_ORDERING
help

155
arch/mips/kernel/smp-cps.c
View file

@ -20,6 +20,7 @@
#include <asm/mips-cpc.h>
#include <asm/mips_mt.h>
#include <asm/mipsregs.h>
#include <asm/pm-cps.h>
#include <asm/smp-cps.h>
#include <asm/time.h>
#include <asm/uasm.h>
@ -194,10 +195,12 @@ static void cps_boot_secondary(int cpu, struct task_struct *idle)
atomic_or(1 << cpu_vpe_id(&cpu_data[cpu]), &core_cfg->vpe_mask);
preempt_disable();
if (!test_bit(core, core_power)) {
/* Boot a VPE on a powered down core */
boot_core(core);
return;
goto out;
}
if (core != current_cpu_data.core) {
@ -214,13 +217,15 @@ static void cps_boot_secondary(int cpu, struct task_struct *idle)
NULL, 1);
if (err)
panic("Failed to call remote CPU\n");
return;
goto out;
}
BUG_ON(!cpu_has_mipsmt);
/* Boot a VPE on this core */
mips_cps_boot_vpes();
out:
preempt_enable();
}
static void cps_init_secondary(void)
@ -250,6 +255,148 @@ static void cps_cpus_done(void)
{
}
#ifdef CONFIG_HOTPLUG_CPU
static int cps_cpu_disable(void)
{
unsigned cpu = smp_processor_id();
struct core_boot_config *core_cfg;
if (!cpu)
return -EBUSY;
if (!cps_pm_support_state(CPS_PM_POWER_GATED))
return -EINVAL;
core_cfg = &mips_cps_core_bootcfg[current_cpu_data.core];
atomic_sub(1 << cpu_vpe_id(&current_cpu_data), &core_cfg->vpe_mask);
smp_mb__after_atomic_dec();
set_cpu_online(cpu, false);
cpu_clear(cpu, cpu_callin_map);
return 0;
}
static DECLARE_COMPLETION(cpu_death_chosen);
static unsigned cpu_death_sibling;
static enum {
CPU_DEATH_HALT,
CPU_DEATH_POWER,
} cpu_death;
void play_dead(void)
{
unsigned cpu, core;
local_irq_disable();
idle_task_exit();
cpu = smp_processor_id();
cpu_death = CPU_DEATH_POWER;
if (cpu_has_mipsmt) {
core = cpu_data[cpu].core;
/* Look for another online VPE within the core */
for_each_online_cpu(cpu_death_sibling) {
if (cpu_data[cpu_death_sibling].core != core)
continue;
/*
* There is an online VPE within the core. Just halt
* this TC and leave the core alone.
*/
cpu_death = CPU_DEATH_HALT;
break;
}
}
/* This CPU has chosen its way out */
complete(&cpu_death_chosen);
if (cpu_death == CPU_DEATH_HALT) {
/* Halt this TC */
write_c0_tchalt(TCHALT_H);
instruction_hazard();
} else {
/* Power down the core */
cps_pm_enter_state(CPS_PM_POWER_GATED);
}
/* This should never be reached */
panic("Failed to offline CPU %u", cpu);
}
static void wait_for_sibling_halt(void *ptr_cpu)
{
unsigned cpu = (unsigned)ptr_cpu;
unsigned vpe_id = cpu_data[cpu].vpe_id;
unsigned halted;
unsigned long flags;
do {
local_irq_save(flags);
settc(vpe_id);
halted = read_tc_c0_tchalt();
local_irq_restore(flags);
} while (!(halted & TCHALT_H));
}
static void cps_cpu_die(unsigned int cpu)
{
unsigned core = cpu_data[cpu].core;
unsigned stat;
int err;
/* Wait for the cpu to choose its way out */
if (!wait_for_completion_timeout(&cpu_death_chosen,
msecs_to_jiffies(5000))) {
pr_err("CPU%u: didn't offline\n", cpu);
return;
}
/*
* Now wait for the CPU to actually offline. Without doing this that
* offlining may race with one or more of:
*
* - Onlining the CPU again.
* - Powering down the core if another VPE within it is offlined.
* - A sibling VPE entering a non-coherent state.
*
* In the non-MT halt case (ie. infinite loop) the CPU is doing nothing
* with which we could race, so do nothing.
*/
if (cpu_death == CPU_DEATH_POWER) {
/*
* Wait for the core to enter a powered down or clock gated
* state, the latter happening when a JTAG probe is connected
* in which case the CPC will refuse to power down the core.
*/
do {
mips_cpc_lock_other(core);
stat = read_cpc_co_stat_conf();
stat &= CPC_Cx_STAT_CONF_SEQSTATE_MSK;
mips_cpc_unlock_other();
} while (stat != CPC_Cx_STAT_CONF_SEQSTATE_D0 &&
stat != CPC_Cx_STAT_CONF_SEQSTATE_D2 &&
stat != CPC_Cx_STAT_CONF_SEQSTATE_U2);
/* Indicate the core is powered off */
bitmap_clear(core_power, core, 1);
} else if (cpu_has_mipsmt) {
/*
* Have a CPU with access to the offlined CPUs registers wait
* for its TC to halt.
*/
err = smp_call_function_single(cpu_death_sibling,
wait_for_sibling_halt,
(void *)cpu, 1);
if (err)
panic("Failed to call remote sibling CPU\n");
}
}
#endif /* CONFIG_HOTPLUG_CPU */
static struct plat_smp_ops cps_smp_ops = {
.smp_setup = cps_smp_setup,
.prepare_cpus = cps_prepare_cpus,
@ -259,6 +406,10 @@ static struct plat_smp_ops cps_smp_ops = {
.send_ipi_single = gic_send_ipi_single,
.send_ipi_mask = gic_send_ipi_mask,
.cpus_done = cps_cpus_done,
#ifdef CONFIG_HOTPLUG_CPU
.cpu_disable = cps_cpu_disable,
.cpu_die = cps_cpu_die,
#endif
};
bool mips_cps_smp_in_use(void)