[PATCH v4 03/15] ARM: mcpm: introduce helpers for platform coherency exit/setup

[Olof Johansson]

Hi,

Just two nits below. One could be fixed incrementally, the other is
a longer-term potential cleanup.

On Tue, Feb 05, 2013 at 12:22:00AM -0500, Nicolas Pitre wrote:

> diff --git a/arch/arm/include/asm/mcpm_entry.h b/arch/arm/include/asm/mcpm_entry.h
> index 3286d5eb91..e76652209d 100644
> --- a/arch/arm/include/asm/mcpm_entry.h
> +++ b/arch/arm/include/asm/mcpm_entry.h
> @@ -15,8 +15,37 @@
>  #define MAX_CPUS_PER_CLUSTER	4
>  #define MAX_NR_CLUSTERS		2
>  
> +/* Definitions for mcpm_sync_struct */
> +#define CPU_DOWN		0x11
> +#define CPU_COMING_UP		0x12
> +#define CPU_UP			0x13
> +#define CPU_GOING_DOWN		0x14
> +
> +#define CLUSTER_DOWN		0x21
> +#define CLUSTER_UP		0x22
> +#define CLUSTER_GOING_DOWN	0x23
> +
> +#define INBOUND_NOT_COMING_UP	0x31
> +#define INBOUND_COMING_UP	0x32
> +
> +/* This is a complete guess. */
> +#define __CACHE_WRITEBACK_ORDER	6
> +#define __CACHE_WRITEBACK_GRANULE (1 << __CACHE_WRITEBACK_ORDER)

Something a little more educational could be useful here. It needs to
be the max writeback/line size of the supported platforms of the binary
kernel, i.e. if someone builds an SoC with 128-byte L2 cache lines this
guess will break.

> +/* Offsets for the mcpm_sync_struct members, for use in asm: */
> +#define MCPM_SYNC_CLUSTER_CPUS	0
> +#define MCPM_SYNC_CPU_SIZE	__CACHE_WRITEBACK_GRANULE
> +#define MCPM_SYNC_CLUSTER_CLUSTER \
> +	(MCPM_SYNC_CLUSTER_CPUS + MCPM_SYNC_CPU_SIZE * MAX_CPUS_PER_CLUSTER)
> +#define MCPM_SYNC_CLUSTER_INBOUND \
> +	(MCPM_SYNC_CLUSTER_CLUSTER + __CACHE_WRITEBACK_GRANULE)
> +#define MCPM_SYNC_CLUSTER_SIZE \
> +	(MCPM_SYNC_CLUSTER_INBOUND + __CACHE_WRITEBACK_GRANULE)
> +
>  #ifndef __ASSEMBLY__
>  
> +#include <linux/types.h>
> +
>  /*
>   * Platform specific code should use this symbol to set up secondary
>   * entry location for processors to use when released from reset.
> @@ -123,5 +152,39 @@ struct mcpm_platform_ops {
>   */
>  int __init mcpm_platform_register(const struct mcpm_platform_ops *ops);
>  
> +/* Synchronisation structures for coordinating safe cluster setup/teardown: */
> +
> +/*
> + * When modifying this structure, make sure you update the MCPM_SYNC_ defines
> + * to match.
> + */

It would be nice to introduce something like arch/powerpc/kernel/asm-offsets.c
on ARM to generate the ASM-side automatically from the C struct instead for
this and other cases, but that's unrelated to this addition.

> +struct mcpm_sync_struct {
> +	/* individual CPU states */
> +	struct {
> +		volatile s8 cpu __aligned(__CACHE_WRITEBACK_GRANULE);
> +	} cpus[MAX_CPUS_PER_CLUSTER];
> +
> +	/* cluster state */
> +	volatile s8 cluster __aligned(__CACHE_WRITEBACK_GRANULE);
> +
> +	/* inbound-side state */
> +	volatile s8 inbound __aligned(__CACHE_WRITEBACK_GRANULE);
> +};


-Olof