linux-kernel - [RFC] PM: domains: Skip disabling unused domains if provider has sync

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Date:   Fri, 27 Jan 2023 01:40:13 +0200
From:   Abel Vesa <abel.vesa@...aro.org>
To:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        linux-pm@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>
Subject: [RFC] PM: domains: Skip disabling unused domains if provider has sync_state

Currently, there are cases when a domain needs to remain enabled until
the consumer driver probes. Sometimes such consumer drivers may be built
as modules. Since the genpd_power_off_unused is called too early for
such consumer driver modules to get a chance to probe, the domain, since
it is unused, will get disabled. On the other hand, the best time for
an unused domain to be disabled is on the provider's sync_state
callback. So, if the provider has registered a sync_state callback,
assume the unused domains for that provider will be disabled on its
sync_state callback.

Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
---

This approach has been applied for unused clocks as well.
With this patch merged in, all the providers that have sync_state
callback registered will leave the domains enabled unless the provider's
sync_state callback explicitly disables them. So those providers will
need to add the disabling part to their sync_state callback. On the
other hand, the platforms that have cases where domains need to remain
enabled (even if unused) until the consumer driver probes, will be able,
with this patch in, to run without the pd_ignore_unused kernel argument,
which seems to be the case for most Qualcomm platforms, at this moment.

 drivers/base/power/domain.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 84662d338188..8e72e8e38c77 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1099,7 +1099,8 @@ static int __init genpd_power_off_unused(void)
 	mutex_lock(&gpd_list_lock);

 	list_for_each_entry(genpd, &gpd_list, gpd_list_node)
-		genpd_queue_power_off_work(genpd);
+		if (!dev_has_sync_state(genpd->provider->dev))
+			genpd_queue_power_off_work(genpd);

 	mutex_unlock(&gpd_list_lock);

-- 
2.34.1