[PATCH v3 2/3] opp/of: Allow empty opp-table with opp-shared

From: Nicola Mazzucato <nicola.mazzucato@arm.com>
To: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org,
	devicetree@vger.kernel.org, sudeep.holla@arm.com,
	rjw@rjwysocki.net, vireshk@kernel.org, robh+dt@kernel.org,
	sboyd@kernel.org, nm@ti.com, daniel.lezcano@linaro.org
Cc: morten.rasmussen@arm.com, chris.redpath@arm.com,
	nicola.mazzucato@arm.com
Subject: [PATCH v3 2/3] opp/of: Allow empty opp-table with opp-shared
Date: Mon,  2 Nov 2020 12:01:14 +0000	[thread overview]
Message-ID: <20201102120115.29993-3-nicola.mazzucato@arm.com> (raw)
In-Reply-To: <20201102120115.29993-1-nicola.mazzucato@arm.com>

The opp binding now allows to have an empty opp table and shared-opp to
merely describe a hw connection among devices (f/v lines).

When initialising an opp table, allow such case by:
- treating some errors as warnings
- do not mark empty tables as shared
- don't fail on empty table

Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
---
 drivers/opp/of.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/opp/of.c b/drivers/opp/of.c
index 874b58756220..b0230490bb31 100644
--- a/drivers/opp/of.c
+++ b/drivers/opp/of.c
@@ -157,6 +157,11 @@ static void _opp_table_free_required_tables(struct opp_table *opp_table)
 /*
  * Populate all devices and opp tables which are part of "required-opps" list.
  * Checking only the first OPP node should be enough.
+ *
+ * Corner case: empty opp table and opp-shared found. In this case we set
+ * unconditionally the opp table access to exclusive, as the opp-shared property
+ * is used purely to describe hw connections. Such information will be retrieved
+ * via dev_pm_opp_of_get_sharing_cpus().
  */
 static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
 					     struct device *dev,
@@ -169,7 +174,9 @@ static void _opp_table_alloc_required_tables(struct opp_table *opp_table,
 	/* Traversing the first OPP node is all we need */
 	np = of_get_next_available_child(opp_np, NULL);
 	if (!np) {
-		dev_err(dev, "Empty OPP table\n");
+		dev_warn(dev, "Empty OPP table\n");
+
+		opp_table->shared_opp = OPP_TABLE_ACCESS_EXCLUSIVE;
 		return;
 	}
 
@@ -377,7 +384,9 @@ int dev_pm_opp_of_find_icc_paths(struct device *dev,
 	struct icc_path **paths;
 
 	ret = _bandwidth_supported(dev, opp_table);
-	if (ret <= 0)
+	if (ret == -EINVAL)
+		return 0; /* Empty OPP table is a valid corner-case, let's not fail */
+	else if (ret <= 0)
 		return ret;
 
 	ret = 0;
-- 
2.27.0

