[PATCH] ARM: imx: disable cpu in .cpu_kill hook

[robherring2@gmail.com (Rob Herring)]

On 01/14/2013 07:09 AM, Shawn Guo wrote:
> It's buggy to disable the cpu that is being hot-unplugged in .cpu_die
> hook which runs on the cpu itself.  Instead, it should be done in
> .cpu_kill which runs on the thread (another cpu) that asks for shutting
> down the cpu.  Move imx_enable_cpu(cpu, false) call into .cpu_kill
> hook, and leave the cpu to be hot-unplugged in WFI with a recovery call
> cpu_leave_lowpower(), so that we can get a more stable cpu hot-plug
> operation.
> 
> Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
> ---
>  arch/arm/mach-imx/common.h  |    1 +
>  arch/arm/mach-imx/hotplug.c |   31 +++++++++++++++++++++++++++----
>  arch/arm/mach-imx/platsmp.c |    1 +
>  3 files changed, 29 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/mach-imx/common.h b/arch/arm/mach-imx/common.h
> index 7191ab4..fa36fb8 100644
> --- a/arch/arm/mach-imx/common.h
> +++ b/arch/arm/mach-imx/common.h
> @@ -142,6 +142,7 @@ extern int imx6q_set_lpm(enum mxc_cpu_pwr_mode mode);
>  extern void imx6q_clock_map_io(void);
>  
>  extern void imx_cpu_die(unsigned int cpu);
> +extern int imx_cpu_kill(unsigned int cpu);
>  
>  #ifdef CONFIG_PM
>  extern void imx6q_pm_init(void);
> diff --git a/arch/arm/mach-imx/hotplug.c b/arch/arm/mach-imx/hotplug.c
> index 3dec962..a9b4096 100644
> --- a/arch/arm/mach-imx/hotplug.c
> +++ b/arch/arm/mach-imx/hotplug.c
> @@ -38,6 +38,22 @@ static inline void cpu_enter_lowpower(void)
>  	  : "cc");
>  }
>  
> +static inline void cpu_leave_lowpower(void)
> +{
> +	unsigned int v;
> +
> +	asm volatile(
> +		"mrc	p15, 0, %0, c1, c0, 0\n"
> +	"	orr	%0, %0, %1\n"
> +	"	mcr	p15, 0, %0, c1, c0, 0\n"

Can't you do:

set_cr(get_cr() | CR_C);

> +	"	mrc	p15, 0, %0, c1, c0, 1\n"
> +	"	orr	%0, %0, %2\n"
> +	"	mcr	p15, 0, %0, c1, c0, 1\n"

Setting or clearing the SMP bit is showing up in multiple places
(big.LITTLE series, Tegra cpuidle). I did inline versions of
set_auxcr/get_auxcr for highbank cpuidle. We should be make those common.

Rob

> +	  : "=&r" (v)
> +	  : "Ir" (CR_C), "Ir" (0x40)
> +	  : "cc");
> +}
> +
>  /*
>   * platform-specific code to shutdown a CPU
>   *
> @@ -45,10 +61,17 @@ static inline void cpu_enter_lowpower(void)
>   */
>  void imx_cpu_die(unsigned int cpu)
>  {
> +	static int spurious;
> +
>  	cpu_enter_lowpower();
> -	imx_enable_cpu(cpu, false);
> +	cpu_do_idle();
> +	cpu_leave_lowpower();
>  
> -	/* spin here until hardware takes it down */
> -	while (1)
> -		;
> +	pr_warn("CPU%u: %u spurious wakeup calls\n", cpu, ++spurious);
> +}
> +
> +int imx_cpu_kill(unsigned int cpu)
> +{
> +	imx_enable_cpu(cpu, false);
> +	return 1;
>  }
> diff --git a/arch/arm/mach-imx/platsmp.c b/arch/arm/mach-imx/platsmp.c
> index 3777b80..66fae88 100644
> --- a/arch/arm/mach-imx/platsmp.c
> +++ b/arch/arm/mach-imx/platsmp.c
> @@ -92,5 +92,6 @@ struct smp_operations  imx_smp_ops __initdata = {
>  	.smp_boot_secondary	= imx_boot_secondary,
>  #ifdef CONFIG_HOTPLUG_CPU
>  	.cpu_die		= imx_cpu_die,
> +	.cpu_kill		= imx_cpu_kill,
>  #endif
>  };
>