lkml.org 
[lkml]   [2019]   [Jul]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 14/18] drivers: firmware: psci: Manage runtime PM in the idle path for CPUs
On Mon, May 13, 2019 at 09:22:56PM +0200, Ulf Hansson wrote:
> When the hierarchical CPU topology layout is used in DT, let's allow the
> CPU to be power managed through its PM domain, via deploying runtime PM
> support.
>
> To know for which idle states runtime PM reference counting is needed,
> let's store the index of deepest idle state for the CPU, in a per CPU
> variable. This allows psci_cpu_suspend_enter() to compare this index with
> the requested idle state index and then act accordingly.

I do not see why a system with two CPU CPUidle states, say CPU retention
and CPU shutdown, should not be calling runtime PM on CPU retention
entry.

The question then is what cluster/package/system states
are allowed for a given CPU idle state, to understand
what idle states can be actually entered at any hierarchy
level given the choice made for the CPU idle state.

In the case above, a CPU entering retention state should prevent
runtime PM selecting a cluster shutdown state; most likely firmware
would demote the request to cluster retention but still, we should
find a way to describe these dependencies.

Thanks,
Lorenzo

> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
>
> Changes:
> - Simplify the code by using the new per CPU struct, that stores the
> needed struct device*.
>
> ---
> drivers/firmware/psci/psci.c | 22 ++++++++++++++++++++--
> 1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index 54e23d4ed0ea..2c4157d3a616 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -20,6 +20,7 @@
> #include <linux/linkage.h>
> #include <linux/of.h>
> #include <linux/pm.h>
> +#include <linux/pm_runtime.h>
> #include <linux/printk.h>
> #include <linux/psci.h>
> #include <linux/reboot.h>
> @@ -298,6 +299,7 @@ static int __init psci_features(u32 psci_func_id)
>
> struct psci_cpuidle_data {
> u32 *psci_states;
> + u32 rpm_state_id;
> struct device *dev;
> };
>
> @@ -385,6 +387,7 @@ static int psci_dt_cpu_init_idle(struct cpuidle_driver *drv,
> goto free_mem;
>
> data->dev = dev;
> + data->rpm_state_id = drv->state_count - 1;
> }
>
> /* Idle states parsed correctly, store them in the per-cpu struct. */
> @@ -481,8 +484,11 @@ static int psci_suspend_finisher(unsigned long index)
> int psci_cpu_suspend_enter(unsigned long index)
> {
> int ret;
> - u32 *state = __this_cpu_read(psci_cpuidle_data.psci_states);
> - u32 composite_state = state[index - 1] | psci_get_domain_state();
> + struct psci_cpuidle_data *data = this_cpu_ptr(&psci_cpuidle_data);
> + u32 *states = data->psci_states;
> + struct device *dev = data->dev;
> + bool runtime_pm = (dev && data->rpm_state_id == index);
> + u32 composite_state;
>
> /*
> * idle state index 0 corresponds to wfi, should never be called
> @@ -491,11 +497,23 @@ int psci_cpu_suspend_enter(unsigned long index)
> if (WARN_ON_ONCE(!index))
> return -EINVAL;
>
> + /*
> + * Do runtime PM if we are using the hierarchical CPU toplogy, but only
> + * when cpuidle have selected the deepest idle state for the CPU.
> + */
> + if (runtime_pm)
> + pm_runtime_put_sync_suspend(dev);
> +
> + composite_state = states[index - 1] | psci_get_domain_state();
> +
> if (!psci_power_state_loses_context(composite_state))
> ret = psci_ops.cpu_suspend(composite_state, 0);
> else
> ret = cpu_suspend(index, psci_suspend_finisher);
>
> + if (runtime_pm)
> + pm_runtime_get_sync(dev);
> +
> /* Clear the domain state to start fresh when back from idle. */
> psci_set_domain_state(0);
>
> --
> 2.17.1
>

\
 
 \ /
  Last update: 2019-07-16 17:54    [W:0.324 / U:63.824 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site