Re: [PATCH 3/3] arm64: psci: Add support to call cpu_suspend with deepest C state.

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Thu, Oct 30, 2014 at 03:55:38AM +0000, Amit Daniel Kachhap wrote:
> This feature will be useful for system suspend/resume which may
> intend to invoke cpu_suspend with deepest possible C state level.

We are working on defining system states in the PSCI specification,
but it is not set in stone yet (Cc'ed Charles).

I guess you are posting this code because you have already an
implementation that supports system suspend/resume, so I am
taking an immediate action to come up with an API suitable
for that asap.

On a side note I do not necessarily like this magic idle index
logic, I prefer adding an API for that, that translates the call
into whatever is required by the back-end (ie PSCI) implementation.

Thanks,
Lorenzo

> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
> ---
>  arch/arm64/include/asm/psci.h | 2 ++
>  arch/arm64/kernel/psci.c      | 8 ++++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/psci.h b/arch/arm64/include/asm/psci.h
> index e5312ea..487e52b 100644
> --- a/arch/arm64/include/asm/psci.h
> +++ b/arch/arm64/include/asm/psci.h
> @@ -14,6 +14,8 @@
>  #ifndef __ASM_PSCI_H
>  #define __ASM_PSCI_H
>  
> +#define CPU_PSCI_IDLE_INDEX_MAX		0xff
> +
>  int psci_init(void);
>  
>  #endif /* __ASM_PSCI_H */
> diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
> index 4ebc146..a761513 100644
> --- a/arch/arm64/kernel/psci.c
> +++ b/arch/arm64/kernel/psci.c
> @@ -70,6 +70,7 @@ enum psci_function {
>  static DEFINE_PER_CPU_READ_MOSTLY(struct psci_power_state *, psci_power_state);
>  
>  static u32 psci_function_id[PSCI_FN_MAX];
> +static u32 cpu_psci_idle_state_count;
>  
>  static int psci_to_linux_errno(int errno)
>  {
> @@ -239,6 +240,8 @@ static int __maybe_unused cpu_psci_cpu_init_idle(struct device_node *cpu_node,
>  	if (!count)
>  		return -ENODEV;
>  
> +	cpu_psci_idle_state_count = count;
> +
>  	psci_states = kcalloc(count, sizeof(*psci_states), GFP_KERNEL);
>  	if (!psci_states)
>  		return -ENOMEM;
> @@ -521,6 +524,11 @@ static int __maybe_unused cpu_psci_cpu_suspend(unsigned long index)
>  {
>  	int ret;
>  	struct psci_power_state *state = __get_cpu_var(psci_power_state);
> +
> +	/* Check and select the deepest idle state */
> +	if (index == CPU_PSCI_IDLE_INDEX_MAX)
> +		index = cpu_psci_idle_state_count;
> +
>  	/*
>  	 * idle state index 0 corresponds to wfi, should never be called
>  	 * from the cpu_suspend operations.
> -- 
> 1.9.1
> 
>