linux-kernel - Re: [PATCH] MIPS: Loongson64: Switch to SYNC

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Message-ID: <CAAhV-H7_QjjemjFYMGRBQck5gKRWhTMqvjXF=prcAGNam-MKGg@mail.gmail.com>
Date: Sun, 14 Jul 2024 10:54:24 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Jiaxun Yang <jiaxun.yang@...goat.com>
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>, linux-mips@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: Loongson64: Switch to SYNC_R4K

On Sun, Jul 14, 2024 at 10:41 AM Jiaxun Yang <jiaxun.yang@...goat.com> wrote:
>
> Nowadays SYNC_R4K is performing better than Loongson64's
> custom sync mechanism.
Loongson64's preciseness is significantly better than SYNC_R4K.

Huacai

>
> Switch to SYNC_R4K to improve performance and reduce code
> duplication.
>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
> ---
> Last minute for 6.11 :-)
> ---
>  arch/mips/Kconfig           |  1 +
>  arch/mips/include/asm/smp.h |  1 -
>  arch/mips/loongson64/smp.c  | 35 ++---------------------------------
>  3 files changed, 3 insertions(+), 34 deletions(-)
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 1236ea122061..e163059dd4d3 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -478,6 +478,7 @@ config MACH_LOONGSON64
>         select BOARD_SCACHE
>         select CSRC_R4K
>         select CEVT_R4K
> +       select SYNC_R4K
>         select FORCE_PCI
>         select ISA
>         select I8259
> diff --git a/arch/mips/include/asm/smp.h b/arch/mips/include/asm/smp.h
> index bc2c240f414b..2427d76f953f 100644
> --- a/arch/mips/include/asm/smp.h
> +++ b/arch/mips/include/asm/smp.h
> @@ -50,7 +50,6 @@ extern int __cpu_logical_map[NR_CPUS];
>  #define SMP_CALL_FUNCTION      0x2
>  /* Octeon - Tell another core to flush its icache */
>  #define SMP_ICACHE_FLUSH       0x4
> -#define SMP_ASK_C0COUNT                0x8
>
>  /* Mask of CPUs which are currently definitely operating coherently */
>  extern cpumask_t cpu_coherent_mask;
> diff --git a/arch/mips/loongson64/smp.c b/arch/mips/loongson64/smp.c
> index 66d049cdcf14..147acd972a07 100644
> --- a/arch/mips/loongson64/smp.c
> +++ b/arch/mips/loongson64/smp.c
> @@ -33,7 +33,6 @@ static void __iomem *ipi_clear0_regs[16];
>  static void __iomem *ipi_status0_regs[16];
>  static void __iomem *ipi_en0_regs[16];
>  static void __iomem *ipi_mailbox_buf[16];
> -static uint32_t core0_c0count[NR_CPUS];
>
>  static u32 (*ipi_read_clear)(int cpu);
>  static void (*ipi_write_action)(int cpu, u32 action);
> @@ -382,11 +381,10 @@ loongson3_send_ipi_mask(const struct cpumask *mask, unsigned int action)
>                 ipi_write_action(cpu_logical_map(i), (u32)action);
>  }
>
> -
>  static irqreturn_t loongson3_ipi_interrupt(int irq, void *dev_id)
>  {
> -       int i, cpu = smp_processor_id();
> -       unsigned int action, c0count;
> +       int cpu = smp_processor_id();
> +       unsigned int action;
>
>         action = ipi_read_clear(cpu);
>
> @@ -399,26 +397,14 @@ static irqreturn_t loongson3_ipi_interrupt(int irq, void *dev_id)
>                 irq_exit();
>         }
>
> -       if (action & SMP_ASK_C0COUNT) {
> -               BUG_ON(cpu != 0);
> -               c0count = read_c0_count();
> -               c0count = c0count ? c0count : 1;
> -               for (i = 1; i < nr_cpu_ids; i++)
> -                       core0_c0count[i] = c0count;
> -               nudge_writes(); /* Let others see the result ASAP */
> -       }
> -
>         return IRQ_HANDLED;
>  }
>
> -#define MAX_LOOPS 800
>  /*
>   * SMP init and finish on secondary CPUs
>   */
>  static 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;
> @@ -432,23 +418,6 @@ static void loongson3_init_secondary(void)
>                      cpu_logical_map(cpu) % loongson_sysconf.cores_per_package);
>         cpu_data[cpu].package =
>                 cpu_logical_map(cpu) / loongson_sysconf.cores_per_package;
> -
> -       i = 0;
> -       core0_c0count[cpu] = 0;
> -       loongson3_send_ipi_single(0, SMP_ASK_C0COUNT);
> -       while (!core0_c0count[cpu]) {
> -               i++;
> -               cpu_relax();
> -       }
> -
> -       if (i > MAX_LOOPS)
> -               i = MAX_LOOPS;
> -       if (cpu_data[cpu].package)
> -               initcount = core0_c0count[cpu] + i;
> -       else /* Local access is faster for loops */
> -               initcount = core0_c0count[cpu] + i/2;
> -
> -       write_c0_count(initcount);
>  }
>
>  static void loongson3_smp_finish(void)
>
> ---
> base-commit: 0b58e108042b0ed28a71cd7edf5175999955b233
> change-id: 20240714-loongson64-cevt-r4k-eb74d4ad984c
>
> Best regards,
> --
> Jiaxun Yang <jiaxun.yang@...goat.com>
>