[PATCH RFC 02/27] PM / Domains: Allow domain power states to be read from DT
Ulf Hansson
ulf.hansson at linaro.org
Thu Dec 10 08:53:18 PST 2015
On 17 November 2015 at 23:37, Lina Iyer <lina.iyer at linaro.org> wrote:
> From: Marc Titinger <mtitinger+renesas at baylibre.com>
>
> From: Marc Titinger <mtitinger at baylibre.com>
>
> This patch allows cluster-level idle-states to being soaked in as
> generic domain power states, in order for the domain governor to chose
> the most efficient power state compatible with the device constraints.
That was possible before this patch, although you are now making it
possible to describe this in DT and also modifying genpd to parse this
information.
Also, I don't get what this has to do with the governor. Of course
that governor needs to care about the multiple states you added in
patch1, but it should do that no matter if the information comes from
DT or not, right.
Please re-phrase this to make it bit more clear.
> Similarly, devices can register power-states into the cluster domain, in
> a manner consistent with idle-states.
I don't get this. Can you please elaborate?
>
> This is a attempt to address device-retention states for devices that
> are not hooked to runtime-pm, but feature a retention state handled by
> the same firmware that handles idle-states. For instance a L2 caches.
I guess whether devices may use runtime PM or not, they still can be
attached to a PM domain with multiple power states?
>
> With Juno, in this example the idle-state 'cluster-sleep-0 ' is known
> from each cluster generic domain, as the deepest sate.
>
> cat /sys/kernel/debug/pm_genpd/*
>
> Domain State name Enter (ns) / Exit (ns)
> -------------------------------------------------------------
> a53_pd cluster-sleep-0 1500000 / 800000
> a57_pd cluster-sleep-0 1500000 / 800000
>
> domain status pstate slaves
> /device runtime status
> -----------------------------------------------------------------------
> a53_pd on
> /devices/system/cpu/cpu0 active
> /devices/system/cpu/cpu3 suspended
> /devices/system/cpu/cpu4 suspended
> /devices/system/cpu/cpu5 suspended
> /devices/platform/D1 suspended
> a57_pd cluster-sleep-0
> /devices/system/cpu/cpu1 suspended
> /devices/system/cpu/cpu2 suspended
>
> Signed-off-by: Marc Titinger <mtitinger+renesas at baylibre.com>
> Signed-off-by: Lina Iyer <lina.iyer at linaro.org>
> [Lina: removed dependency on dynamic states, simplified initalization,
> added of_pm_genpd_init() API]
> ---
> .../devicetree/bindings/power/power_domain.txt | 63 ++++++++++
Please split the documentation of the suggested new DT bindings into a
separate patch that is preceding this one.
Also, you need to send it to the DT maintainers.
> drivers/base/power/domain.c | 128 +++++++++++++++++++++
> include/linux/pm_domain.h | 6 +
> 3 files changed, 197 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/power/power_domain.txt b/Documentation/devicetree/bindings/power/power_domain.txt
> index 025b5e7..e2f542e 100644
> --- a/Documentation/devicetree/bindings/power/power_domain.txt
> +++ b/Documentation/devicetree/bindings/power/power_domain.txt
> @@ -29,6 +29,44 @@ Optional properties:
> specified by this binding. More details about power domain specifier are
> available in the next section.
>
> +- power-states : A phandle of an idle-state that shall be soaked into a
> + generic domain power state. The power-state shall be
> + compatible with "linux,domain-state".
Why mention the Linux specific "generic power domain" here?
Let's instead try to describe this without using specific terminology
from Linux.
> +
> +==Power state==
> +
> +A PM domain power state describes an idle state of a domain and must be
> +have the following properties -
> +
> + - compatible
> + Usage: Required
> + Value type: <stringlist>
> + Definition: Must be "linux,domain-state"
Why do you need a compatible string?
You already have the phandle available, I suppose you can use that
instead of parsing for a new compatible string.
> +
> + - entry-latency-us
> + Usage: Not required if wakeup-latency-us is provided.
> + Value type: <prop-encoded-array>
> + Definition: u32 value representing worst case latency in
> + microseconds required to enter the idle state.
> + The exit-latency-us duration may be guaranteed
> + only after entry-latency-us has passed.
> +
> + - exit-latency-us
> + Usage: Not required if wakeup-latency-us is provided.
> + Value type: <prop-encoded-array>
> + Definition: u32 value representing worst case latency
> + in microseconds required to exit the idle state.
> +
> + - wakeup-latency-us:
> + Usage: Not required if entry-latency-us and exit-latency-us
> + are provided.
> + Value type: <prop-encoded-array>
> + Definition: u32 value representing maximum delay between the
> + signaling the wakeup of the domain and the domain resuming
> + regular operation.
> + If omitted, this is assumed to be equal to:
> + entry-latency-us + exit-latency-us
I think we should decide which of the two alternatives to use, we
shouldn't make it more complicated than needed.
> +
> Example:
>
> power: power-controller at 12340000 {
> @@ -55,6 +93,31 @@ Example 2:
> #power-domain-cells = <1>;
> };
>
> +Example 3:
> +
> + pm-domains {
> + a57_pd: a57_pd@ {
> + /* will have a57 platform ARM_PD_METHOD_OF_DECLARE*/
> + compatible = "arm,pd","arm,cortex-a57";
> + #power-domain-cells = <0>;
> + power-states = <&CLUSTER_SLEEP_0>;
> + };
> +
> + a53_pd: a53_pd@ {
> + /* will have a a53 platform ARM_PD_METHOD_OF_DECLARE*/
> + compatible = "arm,pd","arm,cortex-a53";
> + #power-domain-cells = <0>;
> + power-states = <&CLUSTER_SLEEP_0>;
> + };
> +
> + CLUSTER_SLEEP_0: power-state at 0 {
> + compatible = "pm-domain,power-state";
> + entry-latency-us = <1000>;
> + exit-latency-us = <2000>;
> + };
I think we should also cover the case when power-controller has
"#power-domain-cells = <[n>0]>".
Perhaps extending the first example is then better than adding a new one!?
> + };
> +
> +
> The nodes above define two power controllers: 'parent' and 'child'.
> Domains created by the 'child' power controller are subdomains of '0' power
> domain provided by the 'parent' power controller.
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 3242854..fe1be88 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -35,6 +35,7 @@
> })
>
> #define GENPD_MAX_NAME_SIZE 20
> +#define GENPD_MAX_DOMAIN_STATES 10
Instead of setting a hard limit, let's pre-parse the DTB to get the
number of power states. In that way, it should be fairly easy to
convert the below code to be more dynamic.
>
> static int pm_genpd_alloc_states_names(struct generic_pm_domain *genpd,
> const struct genpd_power_state *st,
> @@ -1515,6 +1516,105 @@ static int pm_genpd_default_restore_state(struct device *dev)
> return cb ? cb(dev) : 0;
> }
>
> +static const struct of_device_id power_state_match[] = {
> + { .compatible = "linux,domain-state" },
> + { }
> +};
> +
> +static int of_get_genpd_power_state(struct genpd_power_state *genpd_state,
> + struct device_node *state_node)
> +{
> + const struct of_device_id *match_id;
> + int err = 0;
> + u32 latency;
> +
> + match_id = of_match_node(power_state_match, state_node);
> + if (!match_id)
> + return -ENODEV;
> +
> + err = of_property_read_u32(state_node, "wakeup-latency-us", &latency);
> + if (err) {
> + u32 entry_latency, exit_latency;
> +
> + err = of_property_read_u32(state_node, "entry-latency-us",
> + &entry_latency);
> + if (err) {
> + pr_debug(" * %s missing entry-latency-us property\n",
> + state_node->full_name);
> + return -EINVAL;
> + }
> +
> + err = of_property_read_u32(state_node, "exit-latency-us",
> + &exit_latency);
> + if (err) {
> + pr_debug(" * %s missing exit-latency-us property\n",
> + state_node->full_name);
> + return -EINVAL;
> + }
> + /*
> + * If wakeup-latency-us is missing, default to entry+exit
> + * latencies as defined in idle states bindings
> + */
> + latency = entry_latency + exit_latency;
> + }
> +
> + genpd_state->power_on_latency_ns = 1000 * latency;
> +
> + err = of_property_read_u32(state_node, "entry-latency-us", &latency);
> + if (err) {
> + pr_debug(" * %s missing min-residency-us property\n",
> + state_node->full_name);
> + return -EINVAL;
> + }
> +
> + genpd_state->power_off_latency_ns = 1000 * latency;
> +
> + return 0;
> +}
> +
> +static int of_genpd_device_parse_states(struct device_node *np,
> + struct genpd_power_state *genpd_states,
> + int *state_count)
> +{
> + struct device_node *state_node;
> + int i, err = 0;
> +
> + for (i = 0;; i++) {
> + struct genpd_power_state genpd_state;
> +
> + state_node = of_parse_phandle(np, "power-states", i);
> + if (!state_node)
> + break;
> +
> + if (i == GENPD_MAX_DOMAIN_STATES) {
> + err = -ENOMEM;
> + break;
> + }
> +
> + err = of_get_genpd_power_state(&genpd_state, state_node);
> + if (err) {
> + pr_err
> + ("Parsing idle state node %s failed with err %d\n",
> + state_node->full_name, err);
> + err = -EINVAL;
> + break;
> + }
> +#ifdef CONFIG_PM_ADVANCED_DEBUG
> + genpd_state.name = kstrndup(state_node->full_name,
> + GENPD_MAX_NAME_SIZE, GFP_KERNEL);
> + if (!genpd_state.name)
> + err = -ENOMEM;
> +#endif
> + of_node_put(state_node);
> + memcpy(&genpd_states[i], &genpd_state, sizeof(genpd_state));
> +#ifdef CONFIG_PM_ADVANCED_DEBUG
> + kfree(genpd_state.name);
> +#endif
> + }
> + *state_count = i;
> + return err;
> +}
> +
> /**
> * pm_genpd_init - Initialize a generic I/O PM domain object.
> * @genpd: PM domain object to initialize.
> @@ -1596,6 +1696,34 @@ void pm_genpd_init(struct generic_pm_domain *genpd,
> }
> EXPORT_SYMBOL_GPL(pm_genpd_init);
>
> +int of_pm_genpd_init(struct device_node *dn, struct generic_pm_domain *genpd,
> + struct dev_power_governor *gov, bool is_off)
> +{
> + struct genpd_power_state states[GENPD_MAX_DOMAIN_STATES] = { { 0 } };
> + int state_count = GENPD_MAX_DOMAIN_STATES;
> + int ret;
> +
> + if (IS_ERR_OR_NULL(genpd))
> + return -EINVAL;
> +
> + ret = of_genpd_device_parse_states(dn, states, &state_count);
> + if (ret) {
> + pr_err("Error parsing genpd states for %s\n", genpd->name);
> + return ret;
> + }
> +
> + ret = genpd_alloc_states_data(genpd, states, state_count);
> + if (ret) {
> + pr_err("Failed to allocate states for %s\n", genpd->name);
> + return ret;
> + }
> +
> + pm_genpd_init(genpd, gov, is_off);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_pm_genpd_init);
> +
> #ifdef CONFIG_PM_GENERIC_DOMAINS_OF
> /*
> * Device Tree based PM domain providers.
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 11763cf..e425911 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -213,6 +213,8 @@ struct generic_pm_domain *__of_genpd_xlate_onecell(
> void *data);
>
> int genpd_dev_pm_attach(struct device *dev);
> +int of_pm_genpd_init(struct device_node *dn, struct generic_pm_domain *genpd,
> + struct dev_power_governor *gov, bool is_off);
> #else /* !CONFIG_PM_GENERIC_DOMAINS_OF */
> static inline int __of_genpd_add_provider(struct device_node *np,
> genpd_xlate_t xlate, void *data)
> @@ -234,6 +236,10 @@ static inline int genpd_dev_pm_attach(struct device *dev)
> {
> return -ENODEV;
> }
> +
> +static inline int of_pm_genpd_init(struct device_node *dn,
> + struct generic_pm_domain *genpd,
> + struct dev_power_governor *gov, bool is_off) {}
> #endif /* CONFIG_PM_GENERIC_DOMAINS_OF */
>
> static inline int of_genpd_add_provider_simple(struct device_node *np,
> --
> 2.1.4
>
Instead of commenting directly to the changes above, let me instead
raise a couple of concerns for the overall approach.
1)
The case when the power-controller node has "#power-domain-cells =
<[n>0]>", isn't covered by $subject patch. I guess we should fix
that!?
2)
I think that it needs to be the SOC PM domain driver that assigns the
initial value for "genpd->state_idx", as I stated also for patch1 when
I noticed pm_genpd_init() overrides that value.
If you share my view around this, it also means that the parsing of
the DTB for "power-states" needs to be done prior the SOC PM domain
driver assigns this initial value for "genpd->state_idx". Following
your approach in $subject patch, means that its value needs to be
updated *after* pm_genpd_init() have been called, perhaps not ideal.
Can we find a better way to deal with this? Maybe by instead of adding
the of_pm_genpd_init() API, we should provide APIs which manages the
DT parsing and the allocation of the struct genpd_power_state? Just an
idea though.
Kind regards
Uffe
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