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SubjectRe: [PATCH v8 1/6] MIPS: JZ4780: Introduce SMP support.
Hi Zhou,

Le mer. 20 mai 2020 à 15:23, Zhou Yanjie <zhouyanjie@wanyeetech.com> a
écrit :
> Hi Paul,
>
> On 2020年05月20日 03:41, Paul Cercueil wrote:
>> Hi Zhou,
>>
>> Le mar. 19 mai 2020 à 22:35, 周琰杰 (Zhou Yanjie)
>> <zhouyanjie@wanyeetech.com> a écrit :
>>> Forward port smp support from kernel 3.18.3 of CI20_linux
>>> to upstream kernel 5.6.
>>>
>>> Tested-by: H. Nikolaus Schaller <hns@goldelico.com>
>>> Tested-by: Paul Boddie <paul@boddie.org.uk>
>>> Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
>>> Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
>>> ---
>>>
>>> Notes:
>>> v1->v2:
>>> 1.Remove unnecessary "plat_irq_dispatch(void)" in irq-ingenic.c.
>>> 2.Add a timeout check for "jz4780_boot_secondary()" to avoid a
>>> dead loop.
>>> 3.Replace hard code in smp.c with macro.
>>>
>>> v2->v3:
>>> 1.Remove unnecessary "extern void (*r4k_blast_dcache)(void)" in
>>> smp.c.
>>> 2.Use "for_each_of_cpu_node" instead "for_each_compatible_node"
>>> in smp.c.
>>> 3.Use "of_cpu_node_to_id" instead "of_property_read_u32_index"
>>> in smp.c.
>>> 4.Move LCR related operations to jz4780-cgu.c.
>>>
>>> v3->v4:
>>> Rebase on top of kernel 5.6-rc1.
>>>
>>> v4->v5:
>>> 1.Splitting changes involving "jz4780-cgu.c" into separate
>>> commit.
>>> 2.Use "request_irq()" replace "setup_irq()".
>>>
>>> v5->v6:
>>> In order to have a kernel that works on multiple SoCs at the
>>> same
>>> time, use "IS_ENABLED()" replace "#ifdef".
>>>
>>> v6->v7:
>>> 1.SMP has be decoupled from the SoC version.
>>> 2.Add mailboxes 3 and 4 for XBurst.
>>> 3.Adjust code in "jz4780_smp_prepare_cpus()".
>>> 4."jz4780_smp_init()" has be marked "__init".
>>>
>>> v7->v8:
>>> No change.
>>>
>>> arch/mips/include/asm/mach-jz4740/smp.h | 87 +++++++++++
>>> arch/mips/jz4740/Kconfig | 2 +
>>> arch/mips/jz4740/Makefile | 5 +
>>> arch/mips/jz4740/prom.c | 4 +
>>> arch/mips/jz4740/smp-entry.S | 57 +++++++
>>> arch/mips/jz4740/smp.c | 258
>>> ++++++++++++++++++++++++++++++++
>>> arch/mips/kernel/idle.c | 35 ++++-
>>> 7 files changed, 447 insertions(+), 1 deletion(-)
>>> create mode 100644 arch/mips/include/asm/mach-jz4740/smp.h
>>> create mode 100644 arch/mips/jz4740/smp-entry.S
>>> create mode 100644 arch/mips/jz4740/smp.c
>>>
>>> diff --git a/arch/mips/include/asm/mach-jz4740/smp.h
>>> b/arch/mips/include/asm/mach-jz4740/smp.h
>>> new file mode 100644
>>> index 00000000..86f660f
>>> --- /dev/null
>>> +++ b/arch/mips/include/asm/mach-jz4740/smp.h
>>> @@ -0,0 +1,87 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>>> +/*
>>> + * Copyright (C) 2013, Paul Burton <paul.burton@imgtec.com>
>>> + * JZ4780 SMP definitions
>>> + */
>>> +
>>> +#ifndef __MIPS_ASM_MACH_JZ4740_SMP_H__
>>> +#define __MIPS_ASM_MACH_JZ4740_SMP_H__
>>> +
>>> +#define read_c0_corectrl() __read_32bit_c0_register($12, 2)
>>> +#define write_c0_corectrl(val) __write_32bit_c0_register($12, 2,
>>> val)
>>> +
>>> +#define read_c0_corestatus() __read_32bit_c0_register($12, 3)
>>> +#define write_c0_corestatus(val) __write_32bit_c0_register($12, 3,
>>> val)
>>> +
>>> +#define read_c0_reim() __read_32bit_c0_register($12, 4)
>>> +#define write_c0_reim(val) __write_32bit_c0_register($12, 4, val)
>>> +
>>> +#define read_c0_mailbox0() __read_32bit_c0_register($20, 0)
>>> +#define write_c0_mailbox0(val) __write_32bit_c0_register($20, 0,
>>> val)
>>> +
>>> +#define read_c0_mailbox1() __read_32bit_c0_register($20, 1)
>>> +#define write_c0_mailbox1(val) __write_32bit_c0_register($20, 1,
>>> val)
>>> +
>>> +#define read_c0_mailbox2() __read_32bit_c0_register($20, 2)
>>> +#define write_c0_mailbox2(val) __write_32bit_c0_register($20, 2,
>>> val)
>>> +
>>> +#define read_c0_mailbox3() __read_32bit_c0_register($20, 3)
>>> +#define write_c0_mailbox3(val) __write_32bit_c0_register($20, 3,
>>> val)
>>> +
>>> +#define smp_clr_pending(mask) do { \
>>> + unsigned int stat; \
>>> + stat = read_c0_corestatus(); \
>>> + stat &= ~((mask) & 0xff); \
>>> + write_c0_corestatus(stat); \
>>> + } while (0)
>>> +
>>> +/*
>>> + * Core Control register
>>> + */
>>> +#define CORECTRL_SLEEP1M_SHIFT 17
>>> +#define CORECTRL_SLEEP1M (_ULCAST_(0x1) <<
>>> CORECTRL_SLEEP1M_SHIFT)
>>> +#define CORECTRL_SLEEP0M_SHIFT 16
>>> +#define CORECTRL_SLEEP0M (_ULCAST_(0x1) <<
>>> CORECTRL_SLEEP0M_SHIFT)
>>> +#define CORECTRL_RPC1_SHIFT 9
>>> +#define CORECTRL_RPC1 (_ULCAST_(0x1) << CORECTRL_RPC1_SHIFT)
>>> +#define CORECTRL_RPC0_SHIFT 8
>>> +#define CORECTRL_RPC0 (_ULCAST_(0x1) << CORECTRL_RPC0_SHIFT)
>>> +#define CORECTRL_SWRST1_SHIFT 1
>>> +#define CORECTRL_SWRST1 (_ULCAST_(0x1) <<
>>> CORECTRL_SWRST1_SHIFT)
>>> +#define CORECTRL_SWRST0_SHIFT 0
>>> +#define CORECTRL_SWRST0 (_ULCAST_(0x1) <<
>>> CORECTRL_SWRST0_SHIFT)
>>> +
>>> +/*
>>> + * Core Status register
>>> + */
>>> +#define CORESTATUS_SLEEP1_SHIFT 17
>>> +#define CORESTATUS_SLEEP1 (_ULCAST_(0x1) <<
>>> CORESTATUS_SLEEP1_SHIFT)
>>> +#define CORESTATUS_SLEEP0_SHIFT 16
>>> +#define CORESTATUS_SLEEP0 (_ULCAST_(0x1) <<
>>> CORESTATUS_SLEEP0_SHIFT)
>>> +#define CORESTATUS_IRQ1P_SHIFT 9
>>> +#define CORESTATUS_IRQ1P (_ULCAST_(0x1) <<
>>> CORESTATUS_IRQ1P_SHIFT)
>>> +#define CORESTATUS_IRQ0P_SHIFT 8
>>> +#define CORESTATUS_IRQ0P (_ULCAST_(0x1) <<
>>> CORESTATUS_IRQ8P_SHIFT)
>>> +#define CORESTATUS_MIRQ1P_SHIFT 1
>>> +#define CORESTATUS_MIRQ1P (_ULCAST_(0x1) <<
>>> CORESTATUS_MIRQ1P_SHIFT)
>>> +#define CORESTATUS_MIRQ0P_SHIFT 0
>>> +#define CORESTATUS_MIRQ0P (_ULCAST_(0x1) <<
>>> CORESTATUS_MIRQ0P_SHIFT)
>>> +
>>> +/*
>>> + * Reset Entry & IRQ Mask register
>>> + */
>>> +#define REIM_ENTRY_SHIFT 16
>>> +#define REIM_ENTRY (_ULCAST_(0xffff) << REIM_ENTRY_SHIFT)
>>> +#define REIM_IRQ1M_SHIFT 9
>>> +#define REIM_IRQ1M (_ULCAST_(0x1) << REIM_IRQ1M_SHIFT)
>>> +#define REIM_IRQ0M_SHIFT 8
>>> +#define REIM_IRQ0M (_ULCAST_(0x1) << REIM_IRQ0M_SHIFT)
>>> +#define REIM_MBOXIRQ1M_SHIFT 1
>>> +#define REIM_MBOXIRQ1M (_ULCAST_(0x1) <<
>>> REIM_MBOXIRQ1M_SHIFT)
>>> +#define REIM_MBOXIRQ0M_SHIFT 0
>>> +#define REIM_MBOXIRQ0M (_ULCAST_(0x1) <<
>>> REIM_MBOXIRQ0M_SHIFT)
>>> +
>>> +extern void jz4780_smp_init(void);
>>> +extern void jz4780_secondary_cpu_entry(void);
>>> +
>>> +#endif /* __MIPS_ASM_MACH_JZ4740_SMP_H__ */
>>> diff --git a/arch/mips/jz4740/Kconfig b/arch/mips/jz4740/Kconfig
>>> index 412d2fa..2b88557 100644
>>> --- a/arch/mips/jz4740/Kconfig
>>> +++ b/arch/mips/jz4740/Kconfig
>>> @@ -34,9 +34,11 @@ config MACH_JZ4770
>>>
>>> config MACH_JZ4780
>>> bool
>>> + select GENERIC_CLOCKEVENTS_BROADCAST if SMP
>>> select MIPS_CPU_SCACHE
>>> select SYS_HAS_CPU_MIPS32_R2
>>> select SYS_SUPPORTS_HIGHMEM
>>> + select SYS_SUPPORTS_SMP
>>>
>>> config MACH_X1000
>>> bool
>>> diff --git a/arch/mips/jz4740/Makefile b/arch/mips/jz4740/Makefile
>>> index 6de14c0..0a0f024 100644
>>> --- a/arch/mips/jz4740/Makefile
>>> +++ b/arch/mips/jz4740/Makefile
>>> @@ -12,3 +12,8 @@ CFLAGS_setup.o =
>>> -I$(src)/../../../scripts/dtc/libfdt
>>> # PM support
>>>
>>> obj-$(CONFIG_PM) += pm.o
>>> +
>>> +# SMP support
>>> +
>>> +obj-$(CONFIG_SMP) += smp.o
>>> +obj-$(CONFIG_SMP) += smp-entry.o
>>> diff --git a/arch/mips/jz4740/prom.c b/arch/mips/jz4740/prom.c
>>> index ff4555c..4acf5c2c 100644
>>> --- a/arch/mips/jz4740/prom.c
>>> +++ b/arch/mips/jz4740/prom.c
>>> @@ -8,10 +8,14 @@
>>>
>>> #include <asm/bootinfo.h>
>>> #include <asm/fw/fw.h>
>>> +#include <asm/mach-jz4740/smp.h>
>>>
>>> void __init prom_init(void)
>>> {
>>> fw_init_cmdline();
>>> +
>>> + if (IS_ENABLED(CONFIG_SMP))
>>> + jz4780_smp_init();
>>> }
>>>
>>> void __init prom_free_prom_memory(void)
>>> diff --git a/arch/mips/jz4740/smp-entry.S
>>> b/arch/mips/jz4740/smp-entry.S
>>> new file mode 100644
>>> index 00000000..20049a3
>>> --- /dev/null
>>> +++ b/arch/mips/jz4740/smp-entry.S
>>> @@ -0,0 +1,57 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>>> +/*
>>> + * Copyright (C) 2013, Paul Burton <paul.burton@imgtec.com>
>>> + * JZ4780 SMP entry point
>>> + */
>>> +
>>> +#include <asm/addrspace.h>
>>> +#include <asm/asm.h>
>>> +#include <asm/asmmacro.h>
>>> +#include <asm/cacheops.h>
>>> +#include <asm/mipsregs.h>
>>> +
>>> +#define CACHE_SIZE (32 * 1024)
>>> +#define CACHE_LINESIZE 32
>>> +
>>> +.extern jz4780_cpu_entry_sp
>>> +.extern jz4780_cpu_entry_gp
>>> +
>>> +.section .text.smp-entry
>>> +.balign 0x10000
>>> +.set noreorder
>>> +LEAF(jz4780_secondary_cpu_entry)
>>> + mtc0 zero, CP0_CAUSE
>>> +
>>> + li t0, ST0_CU0
>>> + mtc0 t0, CP0_STATUS
>>> +
>>> + /* cache setup */
>>> + li t0, KSEG0
>>> + ori t1, t0, CACHE_SIZE
>>> + mtc0 zero, CP0_TAGLO, 0
>>> +1: cache Index_Store_Tag_I, 0(t0)
>>> + cache Index_Store_Tag_D, 0(t0)
>>> + bne t0, t1, 1b
>>> + addiu t0, t0, CACHE_LINESIZE
>>> +
>>> + /* kseg0 cache attribute */
>>> + mfc0 t0, CP0_CONFIG, 0
>>> + ori t0, t0, CONF_CM_CACHABLE_NONCOHERENT
>>> + mtc0 t0, CP0_CONFIG, 0
>>> +
>>> + /* pagemask */
>>> + mtc0 zero, CP0_PAGEMASK, 0
>>> +
>>> + /* retrieve sp */
>>> + la t0, jz4780_cpu_entry_sp
>>> + lw sp, 0(t0)
>>> +
>>> + /* retrieve gp */
>>> + la t0, jz4780_cpu_entry_gp
>>> + lw gp, 0(t0)
>>> +
>>> + /* jump to the kernel in kseg0 */
>>> + la t0, smp_bootstrap
>>> + jr t0
>>> + nop
>>> + END(jz4780_secondary_cpu_entry)
>>> diff --git a/arch/mips/jz4740/smp.c b/arch/mips/jz4740/smp.c
>>> new file mode 100644
>>> index 00000000..d95d22a
>>> --- /dev/null
>>> +++ b/arch/mips/jz4740/smp.c
>>> @@ -0,0 +1,258 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Copyright (C) 2013, Paul Burton <paul.burton@imgtec.com>
>>> + * JZ4780 SMP
>>> + */
>>> +
>>> +#include <linux/clk.h>
>>> +#include <linux/delay.h>
>>> +#include <linux/interrupt.h>
>>> +#include <linux/of.h>
>>> +#include <linux/sched.h>
>>> +#include <linux/sched/task_stack.h>
>>> +#include <linux/smp.h>
>>> +#include <linux/tick.h>
>>> +#include <asm/mach-jz4740/smp.h>
>>> +#include <asm/smp-ops.h>
>>> +
>>> +static struct clk *cpu_clock_gates[CONFIG_NR_CPUS] = { NULL };
>>> +
>>> +u32 jz4780_cpu_entry_sp;
>>> +u32 jz4780_cpu_entry_gp;
>>> +
>>> +static struct cpumask cpu_running;
>>
>> This cpumask is written, but never read anywhere. Since it's static,
>> I believe it's dead code.
>>
>
> Sure, I will remove it.
>
>>> +
>>> +static DEFINE_SPINLOCK(smp_lock);
>>> +
>>> +static irqreturn_t mbox_handler(int irq, void *dev_id)
>>> +{
>>> + int cpu = smp_processor_id();
>>> + u32 action, status;
>>> +
>>> + spin_lock(&smp_lock);
>>> +
>>> + switch (cpu) {
>>> + case 0:
>>> + action = read_c0_mailbox0();
>>> + write_c0_mailbox0(0);
>>> + break;
>>> + case 1:
>>> + action = read_c0_mailbox1();
>>> + write_c0_mailbox1(0);
>>> + break;
>>> + case 2:
>>> + action = read_c0_mailbox2();
>>> + write_c0_mailbox2(0);
>>> + break;
>>> + case 3:
>>> + action = read_c0_mailbox3();
>>> + write_c0_mailbox3(0);
>>> + break;
>>> + default:
>>> + panic("unhandled cpu %d!", cpu);
>>> + }
>>> +
>>> + /* clear pending mailbox interrupt */
>>> + status = read_c0_corestatus();
>>> + status &= ~(CORESTATUS_MIRQ0P << cpu);
>>> + write_c0_corestatus(status);
>>> +
>>> + spin_unlock(&smp_lock);
>>> +
>>> + if (action & SMP_RESCHEDULE_YOURSELF)
>>> + scheduler_ipi();
>>> + if (action & SMP_CALL_FUNCTION)
>>> + generic_smp_call_function_interrupt();
>>> +
>>> + return IRQ_HANDLED;
>>> +}
>>> +
>>> +static void jz4780_smp_setup(void)
>>> +{
>>> + u32 addr, reim;
>>> + int cpu;
>>> +
>>> + reim = read_c0_reim();
>>> +
>>> + for (cpu = 0; cpu < NR_CPUS; cpu++) {
>>> + __cpu_number_map[cpu] = cpu;
>>> + __cpu_logical_map[cpu] = cpu;
>>> + set_cpu_possible(cpu, true);
>>
>> I assume if you do that, you will have num_possible_cpus() ==
>> NR_CPUS, which is not what you want.
>>
>> Correct me if I'm wrong, but I think you would need to call
>> set_cpu_possible() for each CPU node found.
>>
>
> Yes, the current way is indeed a little problem, it will cause
> num_possible_cpus() == NR_CPUS, I will try to find a better way.

You can do:

for_each_of_cpu_node(cpu_node) {
cpu = of_cpu_node_to_id(cpu_node);
__cpu_number_map[cpu] = cpu;
__cpu_logical_map[cpu] = cpu;
set_cpu_possible(cpu, true);
}


>>> + }
>>> +
>>> + /* mask mailbox interrupts for this core */
>>> + reim &= ~REIM_MBOXIRQ0M;
>>> + write_c0_reim(reim);
>>> +
>>> + /* clear mailboxes & pending mailbox IRQs */
>>> + write_c0_mailbox0(0);
>>> + write_c0_mailbox1(0);
>>
>> Write mailbox2/3 too.
>>
>
> Although the XBurst1 architecture can have up to four cores, but
> JZ4780 only has two. If we need to write all four mailboxes here, do
> we need change the function name to "xburst1_smp_setup" or other
> similar names? This seems more appropriate.

Yes, these functions are not jz4780-specific, you can rename them all.

>>> + write_c0_corestatus(0);
>>> +
>>> + /* set reset entry point */
>>> + addr = KSEG1ADDR((u32)&jz4780_secondary_cpu_entry);
>>> + WARN_ON(addr & ~REIM_ENTRY);
>>> + reim &= ~REIM_ENTRY;
>>> + reim |= addr & REIM_ENTRY;
>>> +
>>> + /* unmask mailbox interrupts for this core */
>>> + reim |= REIM_MBOXIRQ0M;
>>> + write_c0_reim(reim);
>>> + set_c0_status(STATUSF_IP3);
>>> + irq_enable_hazard();
>>> +
>>> + cpumask_set_cpu(cpu, &cpu_running);
>>> +}
>>> +
>>> +static void jz4780_smp_prepare_cpus(unsigned int max_cpus)
>>> +{
>>> + struct device_node *cpu_node;
>>> + unsigned cpu, ctrl;
>>> + int err;
>>> +
>>> + /* setup the mailbox IRQ */
>>> + err = request_irq(MIPS_CPU_IRQ_BASE + 3, mbox_handler,
>>> + IRQF_PERCPU | IRQF_NO_THREAD, "core mailbox", NULL);
>>
>> Please don't hardcode the IRQ number. Instead, it should be read
>> from devicetree, maybe from the 'cpus' node (not sure).
>>
>
> OK, I'll try to figure it out.
>
>>> + if (err)
>>> + pr_err("request_irq() on core mailbox failed\n");
>>> +
>>> + ctrl = read_c0_corectrl();
>>> +
>>> + for_each_of_cpu_node(cpu_node) {
>>> + cpu = of_cpu_node_to_id(cpu_node);
>>> + if (cpu < 0) {
>>> + pr_err("Failed to read index of %s\n",
>>> + cpu_node->full_name);
>>> + continue;
>>> + }
>>> +
>>> + /* use reset entry point from REIM register */
>>> + ctrl |= CORECTRL_RPC0 << cpu;
>>> +
>>> + cpu_clock_gates[cpu] = of_clk_get(cpu_node, 0);
>>> + if (IS_ERR(cpu_clock_gates[cpu])) {
>>> + cpu_clock_gates[cpu] = NULL;
>>> + continue;
>>> + }
>>> +
>>> + err = clk_prepare(cpu_clock_gates[cpu]);
>>> + if (err)
>>> + pr_err("Failed to prepare CPU clock gate\n");
>>
>> I'd suggest to call clk_prepare() in jz4780_boot_secondary(), since
>> you can't handle errors here. That would also avoid the static
>> cpu_clock_gates[] array which can grow quite big since its size is
>> given by NR_CPUS.
>>
>
> Sure, I will move it to jz4780_boot_secondary().
>
>>> + }
>>> +
>>> + write_c0_corectrl(ctrl);
>>> +}
>>> +
>>> +static int jz4780_boot_secondary(int cpu, struct task_struct *idle)
>>> +{
>>> + unsigned long flags;
>>> + u32 ctrl;
>>> +
>>> + spin_lock_irqsave(&smp_lock, flags);
>>> +
>>> + /* ensure the core is in reset */
>>> + ctrl = read_c0_corectrl();
>>> + ctrl |= CORECTRL_SWRST0 << cpu;
>>> + write_c0_corectrl(ctrl);
>>> +
>>> + /* ungate core clock */
>>> + if (cpu_clock_gates[cpu])
>>> + clk_enable(cpu_clock_gates[cpu]);
>>
>> You should check the return value of clk_enable().
>>
>> + break;
>
> Sure.
>
>>> +
>>> + /* set entry sp/gp register values */
>>> + jz4780_cpu_entry_sp = __KSTK_TOS(idle);
>>> + jz4780_cpu_entry_gp = (u32)task_thread_info(idle);
>>> + smp_wmb();
>>> +
>>> + /* take the core out of reset */
>>> + ctrl &= ~(CORECTRL_SWRST0 << cpu);
>>> + write_c0_corectrl(ctrl);
>>> +
>>> + cpumask_set_cpu(cpu, &cpu_running);
>>> +
>>> + spin_unlock_irqrestore(&smp_lock, flags);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static void jz4780_init_secondary(void)
>>> +{
>>> +}
>>> +
>>> +static void jz4780_smp_finish(void)
>>> +{
>>> + u32 reim;
>>> +
>>> + spin_lock(&smp_lock);
>>> +
>>> + /* unmask mailbox interrupts for this core */
>>> + reim = read_c0_reim();
>>> + reim |= REIM_MBOXIRQ0M << smp_processor_id();
>>> + write_c0_reim(reim);
>>> +
>>> + spin_unlock(&smp_lock);
>>> +
>>> + /* unmask interrupts for this core */
>>> + change_c0_status(ST0_IM, STATUSF_IP3 | STATUSF_IP2 |
>>> + STATUSF_IP1 | STATUSF_IP0);
>>> + irq_enable_hazard();
>>> +
>>> + /* force broadcast timer */
>>> + tick_broadcast_force();
>>> +}
>>> +
>>> +static void jz4780_send_ipi_single_locked(int cpu, unsigned int
>>> action)
>>> +{
>>> + u32 mbox;
>>> +
>>> + switch (cpu) {
>>> + case 0:
>>> + mbox = read_c0_mailbox0();
>>> + write_c0_mailbox0(mbox | action);
>>> + break;
>>> + case 1:
>>> + mbox = read_c0_mailbox1();
>>> + write_c0_mailbox1(mbox | action);
>>
>> Handle mailboxes 2/3 too here.
>>
>
> Same to the above, do we need to change the function to a more
> appropriate name?
>
>>> + default:
>>> + panic("unhandled cpu %d!", cpu);
>>> + }
>>> +}
>>> +
>>> +static void jz4780_send_ipi_single(int cpu, unsigned int action)
>>> +{
>>> + unsigned long flags;
>>> +
>>> + spin_lock_irqsave(&smp_lock, flags);
>>> + jz4780_send_ipi_single_locked(cpu, action);
>>> + spin_unlock_irqrestore(&smp_lock, flags);
>>> +}
>>> +
>>> +static void jz4780_send_ipi_mask(const struct cpumask *mask,
>>> + unsigned int action)
>>> +{
>>> + unsigned long flags;
>>> + int cpu;
>>> +
>>> + spin_lock_irqsave(&smp_lock, flags);
>>> +
>>> + for_each_cpu(cpu, mask)
>>> + jz4780_send_ipi_single_locked(cpu, action);
>>> +
>>> + spin_unlock_irqrestore(&smp_lock, flags);
>>> +}
>>> +
>>> +static struct plat_smp_ops jz4780_smp_ops = {
>>> + .send_ipi_single = jz4780_send_ipi_single,
>>> + .send_ipi_mask = jz4780_send_ipi_mask,
>>> + .init_secondary = jz4780_init_secondary,
>>> + .smp_finish = jz4780_smp_finish,
>>> + .boot_secondary = jz4780_boot_secondary,
>>> + .smp_setup = jz4780_smp_setup,
>>> + .prepare_cpus = jz4780_smp_prepare_cpus,
>>> +};
>>> +
>>> +void __init jz4780_smp_init(void)
>>> +{
>>> + register_smp_ops(&jz4780_smp_ops);
>>> +}
>>> diff --git a/arch/mips/kernel/idle.c b/arch/mips/kernel/idle.c
>>> index 37f8e78..d33f2d4 100644
>>> --- a/arch/mips/kernel/idle.c
>>> +++ b/arch/mips/kernel/idle.c
>>> @@ -18,6 +18,7 @@
>>> #include <asm/cpu-type.h>
>>> #include <asm/idle.h>
>>> #include <asm/mipsregs.h>
>>> +#include <asm/r4kcache.h>
>>>
>>> /*
>>> * Not all of the MIPS CPUs have the "wait" instruction available.
>>> Moreover,
>>> @@ -88,6 +89,34 @@ static void __cpuidle rm7k_wait_irqoff(void)
>>> }
>>>
>>> /*
>>> + * The Ingenic jz4780 SMP variant has to write back dirty cache
>>> lines before
>>> + * executing wait. The CPU & cache clock will be gated until we
>>> return from
>>> + * the wait, and if another core attempts to access data from our
>>> data cache
>>> + * during this time then it will lock up.
>>> + */
>>> +void jz4780_smp_wait_irqoff(void)
>>> +{
>>> + unsigned long pending = read_c0_cause() & read_c0_status() &
>>> CAUSEF_IP;
>>> +
>>> + /*
>>> + * Going to idle has a significant overhead due to the cache
>>> flush so
>>> + * try to avoid it if we'll immediately be woken again due to
>>> an IRQ.
>>> + */
>>
>> You could add a fast path here where you just call r4k_wait() if
>> num_online_cpus() < 2.
>>
>
> Please correct me if I'm wrong, if we add it here, when the number of
> CPU cores is greater than 1 (which should be the case on most
> occasions), each call to "jz4780_smp_wait_irqoff" will generate
> additional overhead (judging the number of CPUs), is it better to
> change "if (IS_ENABLED(CONFIG_SMP))" in "case CPU_XBURST" below to
> "if (IS_ENABLED(CONFIG_SMP) && (num_possible_cpus() > 1))"?

Is the number of possible CPUs already known when cpu_wait is set?

Cheers,
-Paul

> Thanks and best regards!
>
>> -Paul
>>
>>> + if (!need_resched() && !pending) {
>>> + r4k_blast_dcache();
>>> +
>>> + __asm__(
>>> + " .set push \n"
>>> + " .set mips3 \n"
>>> + " sync \n"
>>> + " wait \n"
>>> + " .set pop \n");
>>> + }
>>> +
>>> + local_irq_enable();
>>> +}
>>> +
>>> +/*
>>> * Au1 'wait' is only useful when the 32kHz counter is used as
>>> timer,
>>> * since coreclock (and the cp0 counter) stops upon executing it.
>>> Only an
>>> * interrupt can wake it, so they must be enabled before entering
>>> idle modes.
>>> @@ -172,7 +201,6 @@ void __init check_wait(void)
>>> case CPU_CAVIUM_OCTEON_PLUS:
>>> case CPU_CAVIUM_OCTEON2:
>>> case CPU_CAVIUM_OCTEON3:
>>> - case CPU_XBURST:
>>> case CPU_LOONGSON32:
>>> case CPU_XLR:
>>> case CPU_XLP:
>>> @@ -246,6 +274,11 @@ void __init check_wait(void)
>>> cpu_wait = r4k_wait;
>>> */
>>> break;
>>> + case CPU_XBURST:
>>> + if (IS_ENABLED(CONFIG_SMP))
>>> + cpu_wait = jz4780_smp_wait_irqoff;
>>> + else
>>> + cpu_wait = r4k_wait;
>>> default:
>>> break;
>>> }
>>> --
>>> 2.7.4
>>>
>>
>


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