[PATCH v4 14/15] ARM: Enable selection of SMP operations at boot time

[Nicolas Pitre]

On Tue, 5 Feb 2013, Nicolas Pitre wrote:

> From: Jon Medhurst <tixy at linaro.org>
> 
> Add a new 'smp_init' hook to machine_desc so platforms can specify a
> function to be used to setup smp ops instead of having a statically
> defined value.
> 
> Signed-off-by: Jon Medhurst <tixy at linaro.org>
> Signed-off-by: Nicolas Pitre <nicolas.pitre at linaro.org>
> Reviewed-by: Santosh Shilimkar <santosh.shilimkar at ti.com>

I've slightly amended this patch to make its usage more flexible, please 
see below.

> diff --git a/arch/arm/include/asm/mach/arch.h b/arch/arm/include/asm/mach/arch.h
> index 917d4fcfd9..3d01c6d6c3 100644
> --- a/arch/arm/include/asm/mach/arch.h
> +++ b/arch/arm/include/asm/mach/arch.h
> @@ -17,8 +17,10 @@ struct pt_regs;
>  struct smp_operations;
>  #ifdef CONFIG_SMP
>  #define smp_ops(ops) (&(ops))
> +#define smp_init_ops(ops) (&(ops))
>  #else
>  #define smp_ops(ops) (struct smp_operations *)NULL
> +#define smp_init_ops(ops) (void (*)(void))NULL
>  #endif
>  
>  struct machine_desc {
> @@ -42,6 +44,7 @@ struct machine_desc {
>  	unsigned char		reserve_lp2 :1;	/* never has lp2	*/
>  	char			restart_mode;	/* default restart mode	*/
>  	struct smp_operations	*smp;		/* SMP operations	*/
> +	void			(*smp_init)(void);
>  	void			(*fixup)(struct tag *, char **,
>  					 struct meminfo *);
>  	void			(*reserve)(void);/* reserve mem blocks	*/
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 3f6cbb2e3e..41edca8582 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -768,7 +768,10 @@ void __init setup_arch(char **cmdline_p)
>  	arm_dt_init_cpu_maps();
>  #ifdef CONFIG_SMP
>  	if (is_smp()) {
> -		smp_set_ops(mdesc->smp);
> +		if(mdesc->smp_init)
> +			(*mdesc->smp_init)();
> +		else
> +			smp_set_ops(mdesc->smp);
>  		smp_init_cpus();
>  	}
>  #endif

I've amended it with the following changes to deal with an issue 
highlighted by Tixy.  If the runtime hook does not initialize the smp 
ops, the core may continue with a default.  That should let MCPM, PSCI 
and Xen play well together.

diff --git a/arch/arm/include/asm/mach/arch.h b/arch/arm/include/asm/mach/arch.h
index c01bf53b85..af8c54c6c6 100644
--- a/arch/arm/include/asm/mach/arch.h
+++ b/arch/arm/include/asm/mach/arch.h
@@ -19,7 +19,7 @@ struct smp_operations;
 #define smp_init_ops(ops) (&(ops))
 #else
 #define smp_ops(ops) (struct smp_operations *)NULL
-#define smp_init_ops(ops) (void (*)(void))NULL
+#define smp_init_ops(ops) (bool (*)(void))NULL
 #endif
 
 struct machine_desc {
@@ -43,7 +43,7 @@ struct machine_desc {
 	unsigned char		reserve_lp2 :1;	/* never has lp2	*/
 	char			restart_mode;	/* default restart mode	*/
 	struct smp_operations	*smp;		/* SMP operations	*/
-	void			(*smp_init)(void);
+	bool			(*smp_init)(void);
 	void			(*fixup)(struct tag *, char **,
 					 struct meminfo *);
 	void			(*reserve)(void);/* reserve mem blocks	*/
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index e69c580c6f..cf4b08c0f9 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -768,9 +768,7 @@ void __init setup_arch(char **cmdline_p)
 	arm_dt_init_cpu_maps();
 #ifdef CONFIG_SMP
 	if (is_smp()) {
-		if (mdesc->smp_init)
-			mdesc->smp_init();
-		else
+		if (!mdesc->smp_init || !mdesc->smp_init())
 			smp_set_ops(mdesc->smp);
 		smp_init_cpus();
 	}


Nicolas