[RFC PATCH v2 01/15] of: add support for retrieving cpu node for a given logical cpu index
From: Rob Herring <hidden>
Date: 2013-07-17 14:50:56
Also in:
linux-devicetree, linux-pm, lkml
On 07/17/2013 09:06 AM, Sudeep.KarkadaNagesha at arm.com wrote:
From: Sudeep KarkadaNagesha <redacted> Currently different drivers requiring to access cpu device node are parsing the device tree themselves. Since the ordering in the DT need not match the logical cpu ordering, the parsing logic needs to consider that. However, this has resulted in lots of code duplication and in some cases even incorrect logic. It's better to consolidate them by adding support for getting cpu device node for a given logical cpu index in DT core library. However logical to physical index mapping can be architecture specific. This patch adds of_get_cpu_node to retrieve a cpu device node for a given logical cpu index. The default matching of the physical id to the logical cpu index can be overridden by architecture specific code. It is recommended to use these helper function only in pre-SMP/early initialisation stages to retrieve CPU device node pointers in logical ordering. Once the cpu devices are registered, it can be retrieved easily from cpu device of_node which avoids unnecessary parsing and matching. Cc: Rob Herring <redacted> Signed-off-by: Sudeep KarkadaNagesha <redacted>
One comment below, but otherwise for patches 1-4, 8 and 9: Acked-by: Rob Herring <redacted> Also, patch 3 needs to come before patch 2 or the matching will be wrong if patch 3 is not applied.
quoted hunk ↗ jump to hunk
--- drivers/of/base.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/of.h | 5 +++++ 2 files changed, 71 insertions(+)diff --git a/drivers/of/base.c b/drivers/of/base.c index 5c54279..363b8f9 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c@@ -230,6 +230,72 @@ const void *of_get_property(const struct device_node *np, const char *name, } EXPORT_SYMBOL(of_get_property); +/* + * arch_match_cpu_phys_id - Match the given logical CPU and physical id + * + * @cpu: logical index of a cpu + * @phys_id: physical identifier of a cpu + * + * CPU logical to physical index mapping is architecure specific. + * However this __weak function provides a default match of physical + * id to logical cpu index. + * + * Returns 1 if the physical identifier and the logical index correspond + * to the same cpu, 0 otherwise. + */ +int __weak arch_match_cpu_phys_id(int cpu, u64 phys_id) +{ + return (u32)phys_id == cpu; +} + +/** + * of_get_cpu_node - Get device node associated with the given logical CPU + * + * @cpu: CPU number(logical index) for which device node is required + * + * The main purpose of this function is to retrieve the device node for the + * given logical CPU index. It should be used to intialise the of_node in + * cpu device. Once of_node in cpu device is populated, all the further + * references can use that instead. + * + * CPU logical to physical index mapping is architecure specific and is built + * before booting secondary cores. This function uses arch_match_cpu_phys_id + * which can be overridden by architecture specific implementation. + * + * Returns a node pointer for the logical cpu if found, else NULL. + */ +struct device_node *of_get_cpu_node(int cpu) +{ + struct device_node *cpun, *cpus; + const u32 *cell; + u64 hwid; + int ac, prop_len; + + cpus = of_find_node_by_path("/cpus"); + if (WARN(!cpus, "Missing cpus node, bailing out\n"))
What happens on a system with no /cpus nodes? Seems like this is another case of adding new warnings to existing working systems. I'd replace all the WARN's with a single pr_warn on any errors below. For missing /cpus, I would just silently return. Rob
+ return NULL;
+
+ if (WARN_ON(of_property_read_u32(cpus, "#address-cells", &ac)))
+ ac = of_n_addr_cells(cpus);
+
+ for_each_child_of_node(cpus, cpun) {
+ if (of_node_cmp(cpun->type, "cpu"))
+ continue;
+ cell = of_get_property(cpun, "reg", &prop_len);
+ if (WARN(!cell, "%s: missing reg property\n", cpun->full_name))
+ continue;
+
+ while (prop_len) {
+ hwid = of_read_number(cell, ac);
+ prop_len -= ac;
+ if (arch_match_cpu_phys_id(cpu, hwid))
+ return cpun;
+ }
+ }
+
+ return NULL;
+}