Re: [PATCH v2 2/6] of: Add helper for mapping device node to logical CPU number

From: Suzuki K Poulose
Date: Tue Jul 25 2017 - 05:27:40 EST


On 24/07/17 17:42, Sudeep Holla wrote:


On 24/07/17 11:29, Suzuki K Poulose wrote:
Add a helper to map a device node to a logical CPU number to avoid
duplication. Currently this is open coded in different places (e.g
gic-v3, coresight). The helper tries to map device node to a "possible"
logical CPU id, which may not be online yet. It is the responsibility
of the user to make sure that the CPU is online. The helper uses
of_get_cpu_node() which uses arch specific backends to match the phyiscal
ids.

Cc: Rob Herring <robh+dt@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
---
drivers/of/base.c | 26 ++++++++++++++++++++++++++
include/linux/of_device.h | 7 +++++++
2 files changed, 33 insertions(+)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 686628d..639af23 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -420,6 +420,32 @@ struct device_node *of_get_cpu_node(int cpu, unsigned int *thread)
EXPORT_SYMBOL(of_get_cpu_node);

/**
+ * of_device_node_get_cpu: Get the logical CPU number for a given device_node
+ *
+ * @cpu_node: Pointer to the device_node for CPU.
+ *
+ * Returns the logical CPU number of the given CPU device_node.
+ * Returns >= nr_cpu_ids if CPU is not found.
+ */
+int of_device_node_get_cpu(struct device_node *cpu_node)
+{
+ int cpu, thread;
+ bool found = false;
+ struct device_node *np;
+
+ for_each_possible_cpu(cpu) {
+ np = of_get_cpu_node(cpu, &thread);

Ideally, we should be able to use of_cpu_device_node_get instead of
of_get_cpu_node which parses the device tree. Not sure if that's the
case here too.

Sorry for following up on this so late. I had a patch in my tree
for-a-while to address that. Just posted it[1] now seeing this patch now.

You can move to of_cpu_device_node_get if all users of this function are
called after CPU's are registered. Otherwise, you can keep it as is for
now and it can be changed once [1] lands.

As you mentioned offline, since GIC uses this, we need to stick to of_get_cpu_node.
In fact, I started off with the of_cpu_device_node_get() and switched to the former.

It would be really nice to have your patch, which streamlines the interface and we
could switch to that.

Cheers
Suzuki