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Message-ID: <CAPDyKFpFn60O7W71v7b3fsCtmS520=GG0AQhs3GpdarVE+W--A@mail.gmail.com>
Date: Thu, 13 Dec 2018 16:53:44 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Kevin Hilman <khilman@...nel.org>, Pavel Machek <pavel@....cz>,
Len Brown <len.brown@...el.com>,
Linux PM <linux-pm@...r.kernel.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>,
Rajendra Nayak <rnayak@...eaurora.org>,
Niklas Cassel <niklas.cassel@...aro.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 6/6] PM / Domains: Propagate performance state updates
On Wed, 12 Dec 2018 at 11:58, Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> This commit updates genpd core to start propagating performance state
> updates to master domains that have their set_performance_state()
> callback set.
I would appreciate some more words of what happens during the
propagation. For example, how OPP tables are used and how mapping
between performance states are done from a sub-domain to a
master-domain. At least a high level description would be nice, I
think.
>
> Currently a genpd only handles the performance state requirements from
> the devices under its control. This commit extends that to also handle
> the performance state requirement(s) put on the master genpd by its
> sub-domains. There is a separate value required for each master that
> the genpd has and so a new field is added to the struct gpd_link
> (link->performance_state), which represents the link between a genpd and
> its master. The struct gpd_link also got another field
> prev_performance_state, which is used by genpd core as a temporary
> variable during transitions.
>
> Tested-by: Rajendra Nayak <rnayak@...eaurora.org>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> drivers/base/power/domain.c | 105 ++++++++++++++++++++++++++++++------
> include/linux/pm_domain.h | 4 ++
> 2 files changed, 94 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 32ecbefbd191..5e0479b2e976 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -239,24 +239,90 @@ static void genpd_update_accounting(struct generic_pm_domain *genpd)
> static inline void genpd_update_accounting(struct generic_pm_domain *genpd) {}
> #endif
>
> +static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
> + unsigned int state, int depth);
> +
> static int _genpd_set_performance_state(struct generic_pm_domain *genpd,
> - unsigned int state)
> + unsigned int state, int depth)
> {
> + struct generic_pm_domain *master;
> + struct gpd_link *link;
> + unsigned int master_state;
> int ret;
>
> + /* Propagate to masters of genpd */
> + list_for_each_entry(link, &genpd->slave_links, slave_node) {
> + master = link->master;
> +
> + if (!master->set_performance_state)
> + continue;
> +
> + if (unlikely(!state)) {
> + master_state = 0;
> + } else {
> + /* Find master's performance state */
> + master_state = dev_pm_opp_xlate_performance_state(genpd->opp_table,
> + master->opp_table, state);
> + if (unlikely(!master_state)) {
> + ret = -EINVAL;
> + goto err;
> + }
> + }
According to my comment for patch3, the above can be simplified.
Moreover, the "unlikely" thingy above is a bit questionable, as we
can't really know what is "unlikely" here.
> +
> + genpd_lock_nested(master, depth + 1);
> +
> + link->prev_performance_state = link->performance_state;
> + link->performance_state = master_state;
> + ret = _genpd_reeval_performance_state(master, master_state,
> + depth + 1);
> + if (ret)
> + link->performance_state = link->prev_performance_state;
> +
> + genpd_unlock(master);
> +
> + if (ret)
> + goto err;
> + }
> +
> ret = genpd->set_performance_state(genpd, state);
> if (ret)
> - return ret;
> + goto err;
>
> genpd->performance_state = state;
> return 0;
> +
> +err:
> + /* Encountered an error, lets rollback */
> + list_for_each_entry_continue_reverse(link, &genpd->slave_links,
> + slave_node) {
> + master = link->master;
> +
> + if (!master->set_performance_state)
> + continue;
> +
> + genpd_lock_nested(master, depth + 1);
> +
> + master_state = link->prev_performance_state;
> + link->performance_state = master_state;
> +
> + if (_genpd_reeval_performance_state(master, master_state,
> + depth + 1)) {
> + pr_err("%s: Failed to roll back to %d performance state\n",
> + master->name, master_state);
> + }
> +
> + genpd_unlock(master);
> + }
> +
> + return ret;
> }
>
> static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
> - unsigned int state)
> + unsigned int state, int depth)
> {
> struct generic_pm_domain_data *pd_data;
> struct pm_domain_data *pdd;
> + struct gpd_link *link;
>
> /* New requested state is same as Max requested state */
> if (state == genpd->performance_state)
> @@ -274,21 +340,30 @@ static int _genpd_reeval_performance_state(struct generic_pm_domain *genpd,
> state = pd_data->performance_state;
> }
>
> - if (state == genpd->performance_state)
> - return 0;
> -
> /*
> - * We aren't propagating performance state changes of a subdomain to its
> - * masters as we don't have hardware that needs it. Over that, the
> - * performance states of subdomain and its masters may not have
> - * one-to-one mapping and would require additional information. We can
> - * get back to this once we have hardware that needs it. For that
> - * reason, we don't have to consider performance state of the subdomains
> - * of genpd here.
> + * Traverse all sub-domains within the domain. This can be
> + * done without any additional locking as the link->performance_state
> + * field is protected by the master genpd->lock, which is already taken.
> + *
> + * Also note that link->performance_state (subdomain's performance state
> + * requirement to master domain) is different from
> + * link->slave->performance_state (current performance state requirement
> + * of the devices/sub-domains of the subdomain) and so can have a
> + * different value.
> + *
> + * Note that we also take vote from powered-off sub-domains into account
> + * as the same is done for devices right now.
> */
> + list_for_each_entry(link, &genpd->master_links, master_node) {
> + if (link->performance_state > state)
> + state = link->performance_state;
> + }
> +
> + if (state == genpd->performance_state)
> + return 0;
>
> update_state:
> - return _genpd_set_performance_state(genpd, state);
> + return _genpd_set_performance_state(genpd, state, depth);
Instead of calling _genpd_set_performance_state() from here, I suggest
to let the caller do it. Simply return the aggregated new state, if it
needs to be updated - and zero if no update is needed.
Why? I think it may clarify and simplify the code, in regards to the
actual set/propagation of state changes. Another side-effect, is that
you should be able to avoid the forward declaration of
_genpd_reeval_performance_state(), which I think is nice as well.
I guess changing this, should already be done in patch 5, so patch 6
can build on it.
> }
>
> /**
> @@ -332,7 +407,7 @@ int dev_pm_genpd_set_performance_state(struct device *dev, unsigned int state)
> prev = gpd_data->performance_state;
> gpd_data->performance_state = state;
>
> - ret = _genpd_reeval_performance_state(genpd, state);
> + ret = _genpd_reeval_performance_state(genpd, state, 0);
> if (ret)
> gpd_data->performance_state = prev;
>
> diff --git a/include/linux/pm_domain.h b/include/linux/pm_domain.h
> index 9ad101362aef..dd364abb649a 100644
> --- a/include/linux/pm_domain.h
> +++ b/include/linux/pm_domain.h
> @@ -136,6 +136,10 @@ struct gpd_link {
> struct list_head master_node;
> struct generic_pm_domain *slave;
> struct list_head slave_node;
> +
> + /* Sub-domain's per-master domain performance state */
> + unsigned int performance_state;
> + unsigned int prev_performance_state;
Probably a leftover from the earlier versions, please remove.
> };
>
> struct gpd_timing_data {
> --
> 2.19.1.568.g152ad8e3369a
>
Kind regards
Uffe
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