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Subject[PATCH] of: base: Skip CPU nodes with non-"okay"/"disabled" status
Date
Allow fully disabling CPU nodes using status = "fail". Having no status
property at all is still interpreted as "okay" as usual.

This allows a bootloader to change the number of available CPUs (for
example when a common DTS is used for SoC variants with different numbers
of cores) without deleting the nodes altogether, which could require
additional fixups to avoid dangling phandle references.

References:
- https://www.lkml.org/lkml/2020/8/26/1237
- https://www.spinics.net/lists/devicetree-spec/msg01007.html
- https://github.com/devicetree-org/dt-schema/pull/61

Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
---
drivers/of/base.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 61de453b885c..4e9973627c8d 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -650,6 +650,32 @@ bool of_device_is_available(const struct device_node *device)
}
EXPORT_SYMBOL(of_device_is_available);

+/**
+ * __of_device_is_disabled - check if a device has status "disabled"
+ *
+ * @device: Node to check status for, with locks already held
+ *
+ * Return: True if the status property is set to "disabled",
+ * false otherwise
+ *
+ * Most callers should use __of_device_is_available() instead, this function
+ * only exists due to the special interpretation of the "disabled" status for
+ * CPU nodes.
+ */
+static bool __of_device_is_disabled(const struct device_node *device)
+{
+ const char *status;
+
+ if (!device)
+ return false;
+
+ status = __of_get_property(device, "status", NULL);
+ if (status == NULL)
+ return false;
+
+ return !strcmp(status, "disabled");
+}
+
/**
* of_device_is_big_endian - check if a device has BE registers
*
@@ -817,6 +843,9 @@ struct device_node *of_get_next_cpu_node(struct device_node *prev)
of_node_put(node);
}
for (; next; next = next->sibling) {
+ if (!__of_device_is_available(next) &&
+ !__of_device_is_disabled(next))
+ continue;
if (!(of_node_name_eq(next, "cpu") ||
__of_node_is_type(next, "cpu")))
continue;
--
2.17.1
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