[PATCH] cpuidle: psci: Allow PM domain to be initialized even if no OSI mode

From: Ulf Hansson <ulf.hansson@linaro.org>
To: Sudeep Holla <sudeep.holla@arm.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>,
	linux-pm@vger.kernel.org
Cc: "Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Lina Iyer <ilina@codeaurora.org>,
	Lukasz Luba <lukasz.luba@arm.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Stephen Boyd <sboyd@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Benjamin Gaignard <benjamin.gaignard@st.com>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH] cpuidle: psci: Allow PM domain to be initialized even if no OSI mode
Date: Fri, 14 Aug 2020 14:34:36 +0200	[thread overview]
Message-ID: <20200814123436.61851-1-ulf.hansson@linaro.org> (raw)

If the PSCI OSI mode isn't supported or fails to be enabled, the PM domain
topology with the genpd providers isn't initialized. This is perfectly fine
from cpuidle-psci point of view.

However, since the PM domain topology in the DTS files is a description of
the HW, no matter of whether the PSCI OSI mode is supported or not, other
consumers besides the CPUs may rely on it.

Therefore, let's always allow the initialization of the PM domain topology
to succeed, independently of whether the PSCI OSI mode is supported.
Consequentially we need to track if we succeed to enable the OSI mode, as
to know when a domain idlestate can be selected.

Note that, CPU devices are still not being attached to the PM domain
topology, unless the PSCI OSI mode is supported.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
 drivers/cpuidle/cpuidle-psci-domain.c | 49 +++++++++++++--------------
 1 file changed, 24 insertions(+), 25 deletions(-)

diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
index b6e9649ab0da..55653c110e3a 100644
--- a/drivers/cpuidle/cpuidle-psci-domain.c
+++ b/drivers/cpuidle/cpuidle-psci-domain.c
@@ -28,6 +28,7 @@ struct psci_pd_provider {
 
 static LIST_HEAD(psci_pd_providers);
 static bool psci_pd_allow_domain_state;
+static bool psci_osi_mode_enabled;
 
 static int psci_pd_power_off(struct generic_pm_domain *pd)
 {
@@ -37,7 +38,7 @@ static int psci_pd_power_off(struct generic_pm_domain *pd)
 	if (!state->data)
 		return 0;
 
-	if (!psci_pd_allow_domain_state)
+	if (!psci_pd_allow_domain_state || !psci_osi_mode_enabled)
 		return -EBUSY;
 
 	/* OSI mode is enabled, set the corresponding domain state. */
@@ -190,7 +191,7 @@ static void psci_pd_remove(void)
 	}
 }
 
-static int psci_pd_init_topology(struct device_node *np, bool add)
+static int psci_pd_init_topology(struct device_node *np)
 {
 	struct device_node *node;
 	struct of_phandle_args child, parent;
@@ -203,9 +204,7 @@ static int psci_pd_init_topology(struct device_node *np, bool add)
 
 		child.np = node;
 		child.args_count = 0;
-
-		ret = add ? of_genpd_add_subdomain(&parent, &child) :
-			of_genpd_remove_subdomain(&parent, &child);
+		ret = of_genpd_add_subdomain(&parent, &child);
 		of_node_put(parent.np);
 		if (ret) {
 			of_node_put(node);
@@ -216,14 +215,21 @@ static int psci_pd_init_topology(struct device_node *np, bool add)
 	return 0;
 }
 
-static int psci_pd_add_topology(struct device_node *np)
+static void psci_pd_try_set_osi_mode(void)
 {
-	return psci_pd_init_topology(np, true);
-}
+	int ret;
 
-static void psci_pd_remove_topology(struct device_node *np)
-{
-	psci_pd_init_topology(np, false);
+	if (!psci_has_osi_support())
+		return;
+
+	/* Try to enable OSI mode. */
+	ret = psci_set_osi_mode();
+	if (ret) {
+		pr_warn("failed to enable OSI mode: %d\n", ret);
+		return;
+	}
+
+	psci_osi_mode_enabled = true;
 }
 
 static void psci_cpuidle_domain_sync_state(struct device *dev)
@@ -249,10 +255,6 @@ static int psci_cpuidle_domain_probe(struct platform_device *pdev)
 	if (!np)
 		return -ENODEV;
 
-	/* Currently limit the hierarchical topology to be used in OSI mode. */
-	if (!psci_has_osi_support())
-		return 0;
-
 	/*
 	 * Parse child nodes for the "#power-domain-cells" property and
 	 * initialize a genpd/genpd-of-provider pair when it's found.
@@ -273,17 +275,15 @@ static int psci_cpuidle_domain_probe(struct platform_device *pdev)
 		return 0;
 
 	/* Link genpd masters/subdomains to model the CPU topology. */
-	ret = psci_pd_add_topology(np);
+	ret = psci_pd_init_topology(np);
 	if (ret)
 		goto remove_pd;
 
-	/* Try to enable OSI mode. */
-	ret = psci_set_osi_mode();
-	if (ret) {
-		pr_warn("failed to enable OSI mode: %d\n", ret);
-		psci_pd_remove_topology(np);
-		goto remove_pd;
-	}
+	/*
+	 * If OSI mode isn't supported, the topology isn't used by CPUs, but
+	 * it may still be used by other consumers. Leave it initialized.
+	 */
+	psci_pd_try_set_osi_mode();
 
 	pr_info("Initialized CPU PM domain topology\n");
 	return 0;
@@ -291,8 +291,7 @@ static int psci_cpuidle_domain_probe(struct platform_device *pdev)
 put_node:
 	of_node_put(node);
 remove_pd:
-	if (pd_count)
-		psci_pd_remove();
+	psci_pd_remove();
 	pr_err("failed to create CPU PM domains ret=%d\n", ret);
 	return ret;
 }
-- 
2.25.1

