Messages in this thread Patch in this message | | | Date | Mon, 17 Nov 2014 11:16:25 +0000 | From | Will Deacon <> | Subject | Re: [PATCH 08/11] arm: perf: add functions to parse affinity from dt |
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On Fri, Nov 07, 2014 at 04:25:33PM +0000, Mark Rutland wrote: > Depending on hardware configuration, some devices may only be accessible > from certain CPUs, may have interrupts wired up to a subset of CPUs, or > may have operations which affect subsets of CPUs. To handle these > devices it is necessary to describe this affinity information in > devicetree. > > This patch adds functions to handle parsing the CPU affinity of > properties from devicetree, based on Lorenzo's topology binding, > allowing subsets of CPUs to be associated with interrupts, hardware > ports, etc. The functions can be used to build cpumasks and also to test > whether an affinity property only targets one CPU independent of the > current configuration (e.g. when the kernel supports fewer CPUs than are > physically present). This is useful for dealing with mixed SPI/PPI > devices. > > A device may have an arbitrary number of affinity properties, the > meaning of which is device-specific and should be specified in a given > device's binding document. > > For example, an affinity property describing interrupt routing may > consist of a phandle pointing to a subtree of the topology nodes, > indicating the set of CPUs an interrupt originates from or may be taken > on. Bindings may have restrictions on the topology nodes referenced - > for describing coherency controls an affinity property may indicate a > whole cluster (including any non-CPU logic it contains) is affected by > some configuration. > > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > Cc: Grant Likely <grant.likely@linaro.org> > Cc: Rob Herring <rob.herring@kernel.org> > --- > arch/arm/kernel/perf_event_cpu.c | 127 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 127 insertions(+) > > diff --git a/arch/arm/kernel/perf_event_cpu.c b/arch/arm/kernel/perf_event_cpu.c > index ce35149..dfcaba5 100644 > --- a/arch/arm/kernel/perf_event_cpu.c > +++ b/arch/arm/kernel/perf_event_cpu.c > @@ -22,6 +22,7 @@ > #include <linux/export.h> > #include <linux/kernel.h> > #include <linux/of.h> > +#include <linux/of_device.h> > #include <linux/platform_device.h> > #include <linux/slab.h> > #include <linux/spinlock.h> > @@ -294,6 +295,132 @@ static int probe_current_pmu(struct arm_pmu *pmu) > return ret; > } > > +/* > + * Test if the node is within the topology tree. > + * Walk up to the root, keeping refcounts balanced. > + */ > +static bool is_topology_node(struct device_node *node) > +{ > + struct device_node *np, *cpu_map; > + bool ret = false; > + > + cpu_map = of_find_node_by_path("/cpus/cpu-map"); > + if (!cpu_map) > + return false; > + > + /* > + * of_get_next_parent decrements the refcount of the provided node. > + * Increment it first to keep things balanced. > + */ > + for (np = of_node_get(node); np; np = of_get_next_parent(np)) { > + if (np != cpu_map) > + continue; > + > + ret = true; > + break; > + } > + > + of_node_put(np); > + of_node_put(cpu_map); > + return ret; > +}
Wouldn't this be more at home in topology.c, or somewhere where others can make use of it?
Will
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