Re: [PATCH 02/21] ARM: shmobile: Convert to hotplug state machine

Geert Uytterhoeven
2016-09-06T18:05:41Z

Hi Sebastian,

CC linux-renesas-soc

On Tue, Sep 6, 2016 at 7:04 PM, Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
> Install the callbacks via the state machine.

Please describe why this is desirable.

> Cc: Simon Horman <horms@verge.net.au>
> Cc: Magnus Damm <magnus.damm@gmail.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-sh@vger.kernel.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> arch/arm/mach-shmobile/platsmp-scu.c | 26 ++++++++------------------
> include/linux/cpuhotplug.h | 1 +
> 2 files changed, 9 insertions(+), 18 deletions(-)
>
> diff --git a/arch/arm/mach-shmobile/platsmp-scu.c b/arch/arm/mach-shmobile/platsmp-scu.c
> index 8d478f1da265..d1ecaf37d142 100644
> --- a/arch/arm/mach-shmobile/platsmp-scu.c
> +++ b/arch/arm/mach-shmobile/platsmp-scu.c
> @@ -21,26 +21,14 @@
> static phys_addr_t shmobile_scu_base_phys;
> static void __iomem *shmobile_scu_base;
>
> -static int shmobile_smp_scu_notifier_call(struct notifier_block *nfb,
> - unsigned long action, void *hcpu)
> +static int shmobile_scu_cpu_prepare(unsigned int cpu)
> {
> - unsigned int cpu = (long)hcpu;
> -
> - switch (action) {
> - case CPU_UP_PREPARE:
> - /* For this particular CPU register SCU SMP boot vector */
> - shmobile_smp_hook(cpu, virt_to_phys(shmobile_boot_scu),
> - shmobile_scu_base_phys);
> - break;
> - };
> -
> - return NOTIFY_OK;
> + /* For this particular CPU register SCU SMP boot vector */
> + shmobile_smp_hook(cpu, virt_to_phys(shmobile_boot_scu),
> + shmobile_scu_base_phys);
> + return 0;
> }
>
> -static struct notifier_block shmobile_smp_scu_notifier = {
> - .notifier_call = shmobile_smp_scu_notifier_call,
> -};
> -
> void __init shmobile_smp_scu_prepare_cpus(phys_addr_t scu_base_phys,
> unsigned int max_cpus)
> {
> @@ -54,7 +42,9 @@ void __init shmobile_smp_scu_prepare_cpus(phys_addr_t scu_base_phys,
> scu_power_mode(shmobile_scu_base, SCU_PM_NORMAL);
>
> /* Use CPU notifier for reset vector control */
> - register_cpu_notifier(&shmobile_smp_scu_notifier);
> + cpuhp_setup_state_nocalls(CPUHP_ARM_SHMOBILE_SCU_PREPARE,
> + "arm/shmobile-scu:prepare",
> + shmobile_scu_cpu_prepare, NULL);
> }
>
> #ifdef CONFIG_HOTPLUG_CPU
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 0da071ff36d2..008eed0c0787 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -35,6 +35,7 @@ enum cpuhp_state {
> CPUHP_POWERPC_PMAC_PREPARE,
> CPUHP_POWERPC_MMU_CTX_PREPARE,
> CPUHP_NOTIFY_PREPARE,
> + CPUHP_ARM_SHMOBILE_SCU_PREPARE,
> CPUHP_TIMERS_DEAD,
> CPUHP_BRINGUP_CPU,
> CPUHP_AP_IDLE_DEAD,

What's the rationale behind adding all these numbers and always
iterating over all
of them, even though most/all of them cannot be used at the same time
(e.g. CPUHP_SH_SH3X_PREPARE is for SuperH, while
CPUHP_ARM_SHMOBILE_SCU_PREPARE is for ARM)?

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds