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SubjectRe: [PATCH v10 16/27] drivers: firmware: psci: Prepare to use OS initiated suspend mode
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On 29/11/2018 18:46, Ulf Hansson wrote:
> To enable the OS initiated mode, the CPU topology needs to be described
> using the hierarchical model in DT. When used, the idle state bits for the
> CPU are created by ORing the bits for PM domain's idle state.
>
> Let's prepare the PSCI driver to deal with this, via introducing a per CPU
> variable called domain_state and by adding internal helpers to read/write
> the value of the variable.

What are the domain states ? What values can they have ?

> Cc: Lina Iyer <ilina@codeaurora.org>
> Co-developed-by: Lina Iyer <lina.iyer@linaro.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
>
> Changes in v10:
> - Use __this_cpu_read|write() rather than this_cpu_read|write().
>
> ---
> drivers/firmware/psci/psci.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 4f0cbc95e41b..8dbcdecc2ae4 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -87,8 +87,19 @@ static u32 psci_function_id[PSCI_FN_MAX];
> (PSCI_1_0_EXT_POWER_STATE_ID_MASK | \
> PSCI_1_0_EXT_POWER_STATE_TYPE_MASK)
>
> +static DEFINE_PER_CPU(u32, domain_state);
> static u32 psci_cpu_suspend_feature;
>
> +static inline u32 psci_get_domain_state(void)
> +{
> + return __this_cpu_read(domain_state);
> +}
> +
> +static inline void psci_set_domain_state(u32 state)
> +{
> + __this_cpu_write(domain_state, state);
> +}
> +
> static inline bool psci_has_ext_power_state(void)
> {
> return psci_cpu_suspend_feature &
> @@ -187,6 +198,8 @@ static int psci_cpu_on(unsigned long cpuid, unsigned long entry_point)
>
> fn = psci_function_id[PSCI_FN_CPU_ON];
> err = invoke_psci_fn(fn, cpuid, entry_point, 0);
> + /* Clear the domain state to start fresh. */
> + psci_set_domain_state(0);
> return psci_to_linux_errno(err);

I think this change is ambiguous:

- if it is a change of the state because of the cpu_on, then I was
expecting a similar change in cpu_off and the change only if
invoke_psci_fn() succeeds.

- if it is a change to take opportunity of the code path to initialize
the domain state, I suggest to remove it from there and make it very
explicit with static DEFINE_PER_CPU(u32, domain_state) = { 0 };


> }
>
> @@ -409,15 +422,17 @@ int psci_cpu_init_idle(struct cpuidle_driver *drv, unsigned int cpu)
> static int psci_suspend_finisher(unsigned long index)
> {
> u32 *state = __this_cpu_read(psci_power_state);
> + u32 composite_state = state[index - 1] | psci_get_domain_state();
>
> - return psci_ops.cpu_suspend(state[index - 1],
> - __pa_symbol(cpu_resume));
> + return psci_ops.cpu_suspend(composite_state, __pa_symbol(cpu_resume));
> }
>
> int psci_cpu_suspend_enter(unsigned long index)
> {
> int ret;
> u32 *state = __this_cpu_read(psci_power_state);
> + u32 composite_state = state[index - 1] | psci_get_domain_state();
> +
> /*
> * idle state index 0 corresponds to wfi, should never be called
> * from the cpu_suspend operations
> @@ -425,11 +440,14 @@ int psci_cpu_suspend_enter(unsigned long index)
> if (WARN_ON_ONCE(!index))
> return -EINVAL;
>
> - if (!psci_power_state_loses_context(state[index - 1]))
> - ret = psci_ops.cpu_suspend(state[index - 1], 0);
> + if (!psci_power_state_loses_context(composite_state))
> + ret = psci_ops.cpu_suspend(composite_state, 0);
> else
> ret = cpu_suspend(index, psci_suspend_finisher);
>
> + /* Clear the domain state to start fresh when back from idle. */
> + psci_set_domain_state(0);
> +
> return ret;
> }
>
>


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