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Message-ID: <CAPDyKFrTQ0jy_u_oPN3kAXkd+FYMpHmStuU2pm8FHLa_OvXzBA@mail.gmail.com>
Date: Wed, 4 Aug 2021 13:39:55 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Rajendra Nayak <rnayak@...eaurora.org>,
Viresh Kumar <viresh.kumar@...aro.org>
Cc: Bjorn Andersson <bjorn.andersson@...aro.org>,
Linux PM <linux-pm@...r.kernel.org>,
DTML <devicetree@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-arm-msm <linux-arm-msm@...r.kernel.org>,
Stephen Boyd <swboyd@...omium.org>,
Roja Rani Yarubandi <rojay@...eaurora.org>,
Stephan Gerhold <stephan@...hold.net>
Subject: Re: [PATCH v5 1/2] PM / Domains: Add support for 'required-opps' to
set default perf state
On Wed, 4 Aug 2021 at 13:08, Rajendra Nayak <rnayak@...eaurora.org> wrote:
>
>
> On 8/3/2021 10:08 AM, Rajendra Nayak wrote:
> >
> > On 8/2/2021 6:29 PM, Ulf Hansson wrote:
> >> On Tue, 20 Jul 2021 at 09:12, Rajendra Nayak <rnayak@...eaurora.org> wrote:
> >>>
> >>> Some devices within power domains with performance states do not
> >>> support DVFS, but still need to vote on a default/static state
> >>> while they are active. They can express this using the 'required-opps'
> >>> property in device tree, which points to the phandle of the OPP
> >>> supported by the corresponding power-domains.
> >>>
> >>> Add support to parse this information from DT and then set the
> >>> specified performance state during attach and drop it on detach.
> >>> runtime suspend/resume callbacks already have logic to drop/set
> >>> the vote as needed and should take care of dropping the default
> >>> perf state vote on runtime suspend and restore it back on runtime
> >>> resume.
> >>>
> >>> Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
> >>> ---
> >>> drivers/base/power/domain.c | 28 +++++++++++++++++++++++++---
> >>> include/linux/pm_domain.h | 1 +
> >>> 2 files changed, 26 insertions(+), 3 deletions(-)
> >>>
> >>> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> >>> index a934c67..f454031 100644
> >>> --- a/drivers/base/power/domain.c
> >>> +++ b/drivers/base/power/domain.c
> >>> @@ -2598,6 +2598,12 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off)
> >>>
> >>> dev_dbg(dev, "removing from PM domain %s\n", pd->name);
> >>>
> >>> + /* Drop the default performance state */
> >>> + if (dev_gpd_data(dev)->default_pstate) {
> >>> + dev_pm_genpd_set_performance_state(dev, 0);
> >>> + dev_gpd_data(dev)->default_pstate = 0;
> >>> + }
> >>> +
> >>> for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {
> >>> ret = genpd_remove_device(pd, dev);
> >>> if (ret != -EAGAIN)
> >>> @@ -2635,9 +2641,10 @@ static void genpd_dev_pm_sync(struct device *dev)
> >>> static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
> >>> unsigned int index, bool power_on)
> >>> {
> >>> + struct device_node *np;
> >>> struct of_phandle_args pd_args;
> >>> struct generic_pm_domain *pd;
> >>> - int ret;
> >>> + int ret, pstate;
> >>>
> >>> ret = of_parse_phandle_with_args(dev->of_node, "power-domains",
> >>> "#power-domain-cells", index, &pd_args);
> >>> @@ -2675,10 +2682,25 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
> >>> genpd_unlock(pd);
> >>> }
> >>>
> >>> - if (ret)
> >>> + if (ret) {
> >>> genpd_remove_device(pd, dev);
> >>> + return -EPROBE_DEFER;
> >>> + }
> >>> +
> >>> + /* Set the default performance state */
> >>> + np = base_dev->of_node;
> >>
> >> Please use dev->of_node instead (it is set to the same of_node as
> >> base_dev by the callers of __genpd_dev_pm_attach) as it's more
> >> consistent with existing code.
> >>
> >>> + if (of_parse_phandle(np, "required-opps", index)) {
> >>> + pstate = of_get_required_opp_performance_state(np, index);
> >>> + if (pstate < 0) {
> >>> + ret = pstate;
> >>> + dev_err(dev, "failed to set required performance state for power-domain %s: %d\n",
> >>> + pd->name, ret);
> >>> + }
> >>> + dev_pm_genpd_set_performance_state(dev, pstate);
> >>> + dev_gpd_data(dev)->default_pstate = pstate;
> >>
> >> This doesn't look entirely correct to me. If we fail to translate a
> >> required opp to a performance state, we shouldn't try to set it.
> >
> > yeah, that does not seem right at all :(
> >
> >> Perhaps it's also easier to call
> >> of_get_required_opp_performance_state() unconditionally of whether a
> >> "required-opps" specifier exists. If it fails with the translation,
> >> then we just skip setting a default state and continue with returning
> >> 1.
> >>
> >> Would that work?
>
> Looks like calling of_get_required_opp_performance_state() unconditionally
> makes it spit out a pr_err() in case the node is missing "required-opps" property,
> so I posted a v6 [1] with the check in place and adding the missing else
> condition.
I see.
Viresh, would it make sense to remove that print? I mean, the
required-opps property could be considered as optional and it seems a
bit silly that a pre-parsing of the property is needed to figure that
out.
>
> [1] https://lore.kernel.org/patchwork/project/lkml/list/?series=510727
Kind regards
Uffe
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