[PATCHv3 1/1] coresight: Do not default to CPU0 for missing CPU phandle

[Sai Prakash Ranjan]

Coresight platform support assumes that a missing "cpu" phandle
defaults to CPU0. This could be problematic and unnecessarily binds
components to CPU0, where they may not be. Let us make the DT binding
rules a bit stricter by not defaulting to CPU0 for missing "cpu"
affinity information.

Also in coresight etm and cpu-debug drivers, abort the probe
for such cases.

Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
---
 .../bindings/arm/coresight-cpu-debug.txt         |  4 ++--
 .../devicetree/bindings/arm/coresight.txt        |  8 +++++---
 .../hwtracing/coresight/coresight-cpu-debug.c    |  3 +++
 drivers/hwtracing/coresight/coresight-etm3x.c    |  3 +++
 drivers/hwtracing/coresight/coresight-etm4x.c    |  3 +++
 drivers/hwtracing/coresight/coresight-platform.c | 16 ++++++++--------
 6 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt b/Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt
index 298291211ea4..f1de3247c1b7 100644
--- a/Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt
+++ b/Documentation/devicetree/bindings/arm/coresight-cpu-debug.txt
@@ -26,8 +26,8 @@ Required properties:
 		processor core is clocked by the internal CPU clock, so it
 		is enabled with CPU clock by default.
 
-- cpu : the CPU phandle the debug module is affined to. When omitted
-	the module is considered to belong to CPU0.
+- cpu : the CPU phandle the debug module is affined to. Do not assume it
+        to default to CPU0 if omitted.
 
 Optional properties:
 
diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt
index 8a88ddebc1a2..fcc3bacfd8bc 100644
--- a/Documentation/devicetree/bindings/arm/coresight.txt
+++ b/Documentation/devicetree/bindings/arm/coresight.txt
@@ -59,6 +59,11 @@ its hardware characteristcs.
 
 	* port or ports: see "Graph bindings for Coresight" below.
 
+* Additional required property for Embedded Trace Macrocell (version 3.x and
+  version 4.x):
+	* cpu: the cpu phandle this ETM/PTM is affined to. Do not
+	  assume it to default to CPU0 if omitted.
+
 * Additional required properties for System Trace Macrocells (STM):
 	* reg: along with the physical base address and length of the register
 	  set as described above, another entry is required to describe the
@@ -87,9 +92,6 @@ its hardware characteristcs.
 	* arm,cp14: must be present if the system accesses ETM/PTM management
 	  registers via co-processor 14.
 
-	* cpu: the cpu phandle this ETM/PTM is affined to. When omitted the
-	  source is considered to belong to CPU0.
-
 * Optional property for TMC:
 
 	* arm,buffer-size: size of contiguous buffer space for TMC ETR
diff --git a/drivers/hwtracing/coresight/coresight-cpu-debug.c b/drivers/hwtracing/coresight/coresight-cpu-debug.c
index 07a1367c733f..58bfd6319f65 100644
--- a/drivers/hwtracing/coresight/coresight-cpu-debug.c
+++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c
@@ -579,6 +579,9 @@ static int debug_probe(struct amba_device *adev, const struct amba_id *id)
 		return -ENOMEM;
 
 	drvdata->cpu = coresight_get_cpu(dev);
+	if (drvdata->cpu < 0)
+		return drvdata->cpu;
+
 	if (per_cpu(debug_drvdata, drvdata->cpu)) {
 		dev_err(dev, "CPU%d drvdata has already been initialized\n",
 			drvdata->cpu);
diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
index 225c2982e4fe..e2cb6873c3f2 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x.c
@@ -816,6 +816,9 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
 	}
 
 	drvdata->cpu = coresight_get_cpu(dev);
+	if (drvdata->cpu < 0)
+		return drvdata->cpu;
+
 	desc.name  = devm_kasprintf(dev, GFP_KERNEL, "etm%d", drvdata->cpu);
 	if (!desc.name)
 		return -ENOMEM;
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index 7fe266194ab5..7bcac8896fc1 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -1101,6 +1101,9 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 	spin_lock_init(&drvdata->spinlock);
 
 	drvdata->cpu = coresight_get_cpu(dev);
+	if (drvdata->cpu < 0)
+		return drvdata->cpu;
+
 	desc.name = devm_kasprintf(dev, GFP_KERNEL, "etm%d", drvdata->cpu);
 	if (!desc.name)
 		return -ENOMEM;
diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
index 3c5ceda8db24..4990da2c13e9 100644
--- a/drivers/hwtracing/coresight/coresight-platform.c
+++ b/drivers/hwtracing/coresight/coresight-platform.c
@@ -159,16 +159,16 @@ static int of_coresight_get_cpu(struct device *dev)
 	struct device_node *dn;
 
 	if (!dev->of_node)
-		return 0;
+		return -ENODEV;
+
 	dn = of_parse_phandle(dev->of_node, "cpu", 0);
-	/* Affinity defaults to CPU0 */
 	if (!dn)
-		return 0;
+		return -ENODEV;
+
 	cpu = of_cpu_node_to_id(dn);
 	of_node_put(dn);
 
-	/* Affinity to CPU0 if no cpu nodes are found */
-	return (cpu < 0) ? 0 : cpu;
+	return cpu;
 }
 
 /*
@@ -734,14 +734,14 @@ static int acpi_coresight_get_cpu(struct device *dev)
 	struct acpi_device *adev = ACPI_COMPANION(dev);
 
 	if (!adev)
-		return 0;
+		return -ENODEV;
 	status = acpi_get_parent(adev->handle, &cpu_handle);
 	if (ACPI_FAILURE(status))
-		return 0;
+		return -ENODEV;
 
 	cpu = acpi_handle_to_logical_cpuid(cpu_handle);
 	if (cpu >= nr_cpu_ids)
-		return 0;
+		return -ENODEV;
 	return cpu;
 }
 
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