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From: Arnd Bergmann <arnd@arndb.de>
To: Huacai Chen <chenhuacai@loongson.cn>
Cc: Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Airlie <airlied@linux.ie>, Jonathan Corbet <corbet@lwn.net>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Xuefeng Li <lixuefeng@loongson.cn>,
	Yanteng Si <siyanteng@loongson.cn>,
	Huacai Chen <chenhuacai@gmail.com>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: Re: [PATCH V3 20/22] LoongArch: Add multi-processor (SMP) support
Date: Fri, 17 Sep 2021 11:57:04 +0200	[thread overview]
Message-ID: <CAK8P3a0N=SA-E7ChrMrA5Gv6TDMzJ4_QNUN5OzpJWgzyJwcboA@mail.gmail.com> (raw)
In-Reply-To: <20210917035736.3934017-21-chenhuacai@loongson.cn>

On Fri, Sep 17, 2021 at 5:57 AM Huacai Chen <chenhuacai@loongson.cn> wrote:

> +
> +struct task_struct;
> +
> +struct plat_smp_ops {
> +       void (*send_ipi_single)(int cpu, unsigned int action);
> +       void (*send_ipi_mask)(const struct cpumask *mask, unsigned int action);
> +       void (*smp_setup)(void);
> +       void (*prepare_cpus)(unsigned int max_cpus);
> +       int (*boot_secondary)(int cpu, struct task_struct *idle);
> +       void (*init_secondary)(void);
> +       void (*smp_finish)(void);
> +#ifdef CONFIG_HOTPLUG_CPU
> +       int (*cpu_disable)(void);
> +       void (*cpu_die)(unsigned int cpu);
> +#endif
> +};


Do you foresee having more than one implementation of these in the
near future? If not, I would suggest leaving out the extra indirection
and just using direct function calls.

> +#ifdef CONFIG_SMP
> +
> +static inline void plat_smp_setup(void)
> +{
> +       extern const struct plat_smp_ops *mp_ops;       /* private */
> +
> +       mp_ops->smp_setup();
> +}
> +
> +#else /* !CONFIG_SMP */
> +
> +static inline void plat_smp_setup(void) { }
> +
> +#endif /* !CONFIG_SMP */

You could even go further and do what arch/arm64 has, making
SMP support unconditional. This obviously depends on hardware
roadmaps, but if all harfdware you support has multiple cores,
then non-SMP mode just adds complexity.

> +
> +#define MAX_CPUS 64

You CONFIG_NR_CPUS allows up to 256. I think you need to
adjust one of the numbers to match the other, or remove this
definition and just use CONFIG_NR_CPUS directly.

> +
> +static volatile void *ipi_set_regs[MAX_CPUS];
> +static volatile void *ipi_clear_regs[MAX_CPUS];
> +static volatile void *ipi_status_regs[MAX_CPUS];
> +static volatile void *ipi_en_regs[MAX_CPUS];
> +static volatile void *ipi_mailbox_buf[MAX_CPUS];

Why are these 'volatile'? If they are MMIO registers, they
should be __iomem, and accessed using readl()/writel()
 etc

       Arnd

  reply	other threads:[~2021-09-17  9:57 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17  3:57 [PATCH V3 00/22] arch: Add basic LoongArch support Huacai Chen
2021-09-17  3:57 ` [PATCH V3 01/22] Documentation: LoongArch: Add basic documentations Huacai Chen
2021-09-23 20:37   ` Pavel Machek
2021-09-24  4:07     ` Huacai Chen
2021-09-23 20:59   ` Pavel Machek
2021-09-24  4:10     ` Huacai Chen
2021-09-24  6:58       ` Pavel Machek
2021-09-24  7:31         ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 02/22] Documentation/zh_CN: Add basic LoongArch documentations Huacai Chen
2021-09-17  3:57 ` [PATCH V3 03/22] LoongArch: Add elf-related definitions Huacai Chen
2021-09-17  3:57 ` [PATCH V3 04/22] LoongArch: Add writecombine support for drm Huacai Chen
2021-09-17  3:57 ` [PATCH V3 05/22] LoongArch: Add build infrastructure Huacai Chen
2021-09-17  7:53   ` Arnd Bergmann
2021-09-18  4:35     ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 06/22] LoongArch: Add CPU definition headers Huacai Chen
2021-09-17  3:57 ` [PATCH V3 07/22] LoongArch: Add atomic/locking headers Huacai Chen
2021-09-17  3:57 ` [PATCH V3 08/22] LoongArch: Add other common headers Huacai Chen
2021-09-17  3:57 ` [PATCH V3 09/22] LoongArch: Add boot and setup routines Huacai Chen
2021-09-17  8:11   ` Arnd Bergmann
2021-09-18  4:54     ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 10/22] LoongArch: Add exception/interrupt handling Huacai Chen
2021-09-17  3:57 ` [PATCH V3 11/22] LoongArch: Add process management Huacai Chen
2021-09-17  3:57 ` [PATCH V3 12/22] LoongArch: Add memory management Huacai Chen
2021-09-17  3:57 ` [PATCH V3 13/22] LoongArch: Add system call support Huacai Chen
2021-09-17  8:24   ` Arnd Bergmann
2021-09-18  6:55     ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 14/22] LoongArch: Add signal handling support Huacai Chen
2021-09-17  8:26   ` Arnd Bergmann
2021-09-17 21:10   ` Eric W. Biederman
2021-09-18  7:12     ` Huacai Chen
2021-09-19  9:58       ` Arnd Bergmann
2021-09-20  2:36         ` Huacai Chen
2021-09-20 21:14           ` Richard Henderson
2021-09-22  2:43             ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 15/22] LoongArch: Add elf and module support Huacai Chen
2021-09-17  8:28   ` Arnd Bergmann
2021-09-18  7:14     ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 16/22] LoongArch: Add misc common routines Huacai Chen
2021-09-17  6:10   ` Christoph Hellwig
2021-09-17  6:36     ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 17/22] LoongArch: Add some library functions Huacai Chen
2021-09-17  8:33   ` Arnd Bergmann
2021-09-18  7:16     ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 18/22] LoongArch: Add PCI controller support Huacai Chen
2021-09-17  9:02   ` Arnd Bergmann
2021-09-18  7:36     ` Huacai Chen
2021-09-21 22:36       ` Bjorn Helgaas
2021-09-22 15:33         ` Arnd Bergmann
2021-09-17  3:57 ` [PATCH V3 19/22] LoongArch: Add VDSO and VSYSCALL support Huacai Chen
2021-09-17  3:57 ` [PATCH V3 20/22] LoongArch: Add multi-processor (SMP) support Huacai Chen
2021-09-17  9:57   ` Arnd Bergmann [this message]
2021-09-18  7:22     ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 21/22] LoongArch: Add Non-Uniform Memory Access (NUMA) support Huacai Chen
2021-09-17  6:15   ` Christoph Hellwig
2021-09-17  6:40     ` Huacai Chen
2021-09-17  3:57 ` [PATCH V3 22/22] LoongArch: Add Loongson-3 default config file Huacai Chen
2021-09-17  9:59 ` [PATCH V3 00/22] arch: Add basic LoongArch support Arnd Bergmann

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