linux-kernel - [PATCH V3 3/3] OPP: Don't set OPP recursively for a parent genpd

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Date:   Thu, 16 Nov 2023 16:13:07 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Stephan Gerhold <stephan.gerhold@...nkonzept.com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V3 3/3] OPP: Don't set OPP recursively for a parent genpd

Like other frameworks (clk, regulator, etc.) genpd core too takes care
of propagation to performance state to parent genpds. The OPP core
shouldn't attempt the same, or it may result in undefined behavior.

Add checks at various places to take care of the same.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/opp/core.c | 16 +++++++++++++++-
 drivers/opp/of.c   |  7 +++++--
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/opp/core.c b/drivers/opp/core.c
index e08375ed50aa..4f1ca84d9ed0 100644
--- a/drivers/opp/core.c
+++ b/drivers/opp/core.c
@@ -2392,6 +2392,12 @@ static int _opp_attach_genpd(struct opp_table *opp_table, struct device *dev,
 		return -EINVAL;
 	}
 
+	/* Genpd core takes care of propagation to parent genpd */
+	if (opp_table->is_genpd) {
+		dev_err(dev, "%s: Operation not supported for genpds\n", __func__);
+		return -EOPNOTSUPP;
+	}
+
 	/* Checking only the first one is enough ? */
 	if (opp_table->required_devs[0])
 		return 0;
@@ -2453,8 +2459,16 @@ static int _opp_set_required_devs(struct opp_table *opp_table,
 	if (opp_table->required_devs[0])
 		return 0;
 
-	for (i = 0; i < opp_table->required_opp_count; i++)
+	for (i = 0; i < opp_table->required_opp_count; i++) {
+		/* Genpd core takes care of propagation to parent genpd */
+		if (required_devs[i] && opp_table->is_genpd &&
+		    opp_table->required_opp_tables[i]->is_genpd) {
+			dev_err(dev, "%s: Operation not supported for genpds\n", __func__);
+			return -EOPNOTSUPP;
+		}
+
 		opp_table->required_devs[i] = required_devs[i];
+	}
 
 	return 0;
 }
diff --git a/drivers/opp/of.c b/drivers/opp/of.c
index 5a7e294e56b7..f9f0b22bccbb 100644
--- a/drivers/opp/of.c
+++ b/drivers/opp/of.c
@@ -339,8 +339,11 @@ static int _link_required_opps(struct dev_pm_opp *opp, struct opp_table *opp_tab
 	 */
 	if (required_table->is_genpd && opp_table->required_opp_count == 1 &&
 	    !opp_table->required_devs[0]) {
-		if (!WARN_ON(opp->level != OPP_LEVEL_UNSET))
-			opp->level = opp->required_opps[0]->level;
+		/* Genpd core takes care of propagation to parent genpd */
+		if (!opp_table->is_genpd) {
+			if (!WARN_ON(opp->level != OPP_LEVEL_UNSET))
+				opp->level = opp->required_opps[0]->level;
+		}
 	}
 
 	return 0;
-- 
2.31.1.272.g89b43f80a514