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Subject[PATCH v1 2/3] arch_topology: Handle inconsistent binding of CPU raw capacity
Date
There have a corner case is if we use below DT binding:

cpu0: cpu@0 {
compatible = "arm,cortex-a53";
device_type = "cpu";
reg = <0x0 0x0>;
enable-method = "psci";
};

cpu1: cpu@1 {
compatible = "arm,cortex-a53";
device_type = "cpu";
reg = <0x0 0x1>;
enable-method = "psci";
capacity-dmips-mhz = <1024>;
};

In this case, CPU0 node misses to bind "capacity-dmips-mhz" property,
and CPU1 node binds the property, this means the CPU raw capacity
binding is inconsistent across all CPUs.

This patch introduces an extra flag 'cap_property_miss' to indicate that
any previous CPU nodes miss binding for "capacity-dmips-mhz" property,
and any new CPU node contains the property, it detects the inconsistent
binding, and sets 'cap_parsing_failed' to true and frees raw capacity
array.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
drivers/base/arch_topology.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index b81777ae6425..0687576e880b 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -294,6 +294,7 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
struct clk *cpu_clk;
int ret;
u32 cpu_capacity;
+ static bool cap_property_miss;

if (cap_parsing_failed)
return false;
@@ -301,6 +302,20 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
ret = of_property_read_u32(cpu_node, "capacity-dmips-mhz",
&cpu_capacity);
if (!ret) {
+ /*
+ * A previous CPU node misses binding for CPU raw capacity and
+ * current CPU node finds its property "capacity-dmips-mhz",
+ * thus the DT binding for "capacity-dmips-mhz" is inconsistent
+ * across all CPUs. Set 'cap_parsing_failed' flag and drop the
+ * CPU raw capacity values.
+ */
+ if (cap_property_miss) {
+ pr_err("cpu_capacity: binding %pOF raw capacity\n",
+ cpu_node);
+ pr_err("cpu_capacity: partial information: fallback to 1024 for all CPUs\n");
+ goto parsing_failure;
+ }
+
if (!raw_capacity) {
raw_capacity = kcalloc(num_possible_cpus(),
sizeof(*raw_capacity),
@@ -331,12 +346,18 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
pr_err("cpu_capacity: missing %pOF raw capacity\n",
cpu_node);
pr_err("cpu_capacity: partial information: fallback to 1024 for all CPUs\n");
- cap_parsing_failed = true;
- free_raw_capacity();
+ goto parsing_failure;
+ } else {
+ cap_property_miss = true;
}
}

return !ret;
+
+parsing_failure:
+ cap_parsing_failed = true;
+ free_raw_capacity();
+ return !ret;
}

#ifdef CONFIG_CPU_FREQ
--
2.25.1
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