[RFC PATCH v2 1/1] drivers: cpuidle: cpuidle-arm: heterogeneous systems extension
Lorenzo Pieralisi
lorenzo.pieralisi at arm.com
Thu Apr 16 09:10:17 PDT 2015
Some ARM systems (eg big.LITTLE ones) can be composed of CPUs having
different hardware power management configurations and in the context
of CPUidle, different idle states. The generic ARM CPUidle driver
treats all possible CPUs as equal and initializes a common idle driver
through DT idle states for all possible CPUs.
Current driver cannot manage systems where CPUs are heterogeneous
and therefore can have different idle states.
This patch augments the generic ARM CPUidle driver, by adding code that
at boot initializes CPUidle drivers by going through the
cpu_possible_mask and through DT parsing detects the cpus sharing the
same idle states, thus creating the CPUidle drivers cpumasks.
The drivers are then initialized through the DT idle states interface,
that parses and initializes the DT idle states for the cpus set in the
drivers cpumasks.
This patch instantiates a static array of idle drivers, some of which
can turn out to be unused (eg platforms with uniform idle states
on all possible CPUs), and relies on the config option
CPU_IDLE_MULTIPLE_DRIVERS to be selected by default; this can cause a
little memory overhead, but at the same time allows supporting most of
the current and future ARM platforms through a single generic CPUidle
driver.
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Cc: Howard Chen <howard.chen at linaro.org>
Cc: Rob Herring <robh+dt at kernel.org>
Cc: Kevin Hilman <khilman at linaro.org>
Cc: Sudeep Holla <sudeep.holla at arm.com>
Cc: Lina Iyer <lina.iyer at linaro.org>
Cc: Daniel Lezcano <daniel.lezcano at linaro.org>
Cc: Grant Likely <grant.likely at linaro.org>
Cc: Mathieu Poirier <mathieu.poirier at linaro.org>
Cc: Mark Rutland <mark.rutland at arm.com>
---
drivers/cpuidle/Kconfig.arm | 1 +
drivers/cpuidle/cpuidle-arm.c | 176 ++++++++++++++++++++++++++++++++++++------
2 files changed, 152 insertions(+), 25 deletions(-)
diff --git a/drivers/cpuidle/Kconfig.arm b/drivers/cpuidle/Kconfig.arm
index 21340e0..90c6553 100644
--- a/drivers/cpuidle/Kconfig.arm
+++ b/drivers/cpuidle/Kconfig.arm
@@ -3,6 +3,7 @@
#
config ARM_CPUIDLE
bool "Generic ARM/ARM64 CPU idle Driver"
+ select CPU_IDLE_MULTIPLE_DRIVERS
select DT_IDLE_STATES
help
Select this to enable generic cpuidle driver for ARM.
diff --git a/drivers/cpuidle/cpuidle-arm.c b/drivers/cpuidle/cpuidle-arm.c
index 545069d..251fa2a 100644
--- a/drivers/cpuidle/cpuidle-arm.c
+++ b/drivers/cpuidle/cpuidle-arm.c
@@ -14,6 +14,7 @@
#include <linux/cpuidle.h>
#include <linux/cpumask.h>
#include <linux/cpu_pm.h>
+#include <linux/of_device.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
@@ -58,23 +59,27 @@ static int arm_enter_idle_state(struct cpuidle_device *dev,
return ret ? -1 : idx;
}
-static struct cpuidle_driver arm_idle_driver = {
- .name = "arm_idle",
- .owner = THIS_MODULE,
- /*
- * State at index 0 is standby wfi and considered standard
- * on all ARM platforms. If in some platforms simple wfi
- * can't be used as "state 0", DT bindings must be implemented
- * to work around this issue and allow installing a special
- * handler for idle state index 0.
- */
- .states[0] = {
- .enter = arm_enter_idle_state,
- .exit_latency = 1,
- .target_residency = 1,
- .power_usage = UINT_MAX,
- .name = "WFI",
- .desc = "ARM WFI",
+#define ARM_CPUIDLE_MAX_DRIVERS 2
+
+static struct cpuidle_driver arm_idle_drivers[ARM_CPUIDLE_MAX_DRIVERS] = {
+ [0 ... ARM_CPUIDLE_MAX_DRIVERS - 1] = {
+ .name = "arm_idle",
+ .owner = THIS_MODULE,
+ /*
+ * State at index 0 is standby wfi and considered standard
+ * on all ARM platforms. If in some platforms simple wfi
+ * can't be used as "state 0", DT bindings must be implemented
+ * to work around this issue and allow installing a special
+ * handler for idle state index 0.
+ */
+ .states[0] = {
+ .enter = arm_enter_idle_state,
+ .exit_latency = 1,
+ .target_residency = 1,
+ .power_usage = UINT_MAX,
+ .name = "WFI",
+ .desc = "ARM WFI",
+ }
}
};
@@ -85,17 +90,68 @@ static const struct of_device_id arm_idle_state_match[] __initconst = {
};
/*
- * arm_idle_init
+ * Compare idle states phandle properties
*
- * Registers the arm specific cpuidle driver with the cpuidle
- * framework. It relies on core code to parse the idle states
- * and initialize them using driver data structures accordingly.
+ * Return true if properties are valid and equal, false otherwise
*/
-static int __init arm_idle_init(void)
+static bool __init idle_states_cmp(struct property *states1,
+ struct property *states2)
+{
+ /*
+ * NB: Implemented through code from drivers/of/unittest.c
+ * Function is generic and can be moved to generic OF code
+ * if needed
+ */
+ return states1 && states2 &&
+ (states1->length == states2->length) &&
+ states1->value && states2->value &&
+ !memcmp(states1->value, states2->value, states1->length);
+}
+
+static int __init arm_idle_init_driver(struct cpuidle_driver *drv)
{
- int cpu, ret;
- struct cpuidle_driver *drv = &arm_idle_driver;
+ int ret, cpu;
struct cpuidle_device *dev;
+ struct property *curr_idle_states, *idle_states = NULL;
+ struct device_node *cpu_node;
+
+ for_each_cpu(cpu, drv->cpumask) {
+ cpu_node = of_cpu_device_node_get(cpu);
+ curr_idle_states = of_find_property(cpu_node,
+ "cpu-idle-states", NULL);
+ of_node_put(cpu_node);
+
+ /*
+ * Stash the first valid idle states phandle in the cpumask.
+ * If curr_idle_states is NULL assigning it to idle_states
+ * is harmless and it is managed by idle states comparison
+ * code. Keep track of first valid phandle so that
+ * subsequent cpus can compare against it.
+ */
+ if (!idle_states)
+ idle_states = curr_idle_states;
+
+ /*
+ * If idle states phandles are not equal, remove the
+ * cpu from the driver mask since a CPUidle driver
+ * is only capable of managing uniform idle states.
+ *
+ * Comparison works also when idle_states and
+ * curr_idle_states are the same property, since
+ * they can be == NULL so the cpu must be removed from
+ * the driver mask in that case too (ie cpu has no idle
+ * states).
+ */
+ if (!idle_states_cmp(idle_states, curr_idle_states))
+ cpumask_clear_cpu(cpu, drv->cpumask);
+ }
+
+ /*
+ * If there are no valid states for this driver we rely on arch
+ * default idle behaviour, bail out
+ */
+ if (!idle_states)
+ return -ENODEV;
/*
* Initialize idle states data, starting at index 1.
@@ -117,7 +173,7 @@ static int __init arm_idle_init(void)
* Call arch CPU operations in order to initialize
* idle states suspend back-end specific data
*/
- for_each_possible_cpu(cpu) {
+ for_each_cpu(cpu, drv->cpumask) {
ret = arm_cpuidle_init(cpu);
/*
@@ -157,7 +213,77 @@ out_fail:
}
cpuidle_unregister_driver(drv);
+ return ret;
+}
+
+/*
+ * arm_idle_init
+ *
+ * Registers the arm specific cpuidle driver(s) with the cpuidle
+ * framework. It relies on core code to parse the idle states
+ * and initialize them using driver data structures accordingly.
+ */
+static int __init arm_idle_init(void)
+{
+ int i, ret = -ENODEV;
+ struct cpuidle_driver *drv;
+ cpumask_var_t tmpmask;
+
+ /*
+ * These drivers require DT idle states to be present.
+ * If no idle states are detected there is no reason to
+ * proceed any further hence we return early.
+ */
+ if (!of_find_node_by_name(NULL, "idle-states"))
+ return -ENODEV;
+
+ if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL))
+ return -ENOMEM;
+
+ /*
+ * We need to vet idle states to create CPUidle drivers
+ * that share a common set of them. Create a tmp mask
+ * that we use to keep track of initialized cpus.
+ * Start off by initializing the mask with all possible
+ * cpus, we clear it as we go, till either all cpus
+ * have a CPUidle driver initialized or there are some
+ * CPUs that have no idle states or a parsing error
+ * occurs.
+ */
+ cpumask_copy(tmpmask, cpu_possible_mask);
+
+ for (i = 0; !cpumask_empty(tmpmask); i++) {
+ if (i == ARM_CPUIDLE_MAX_DRIVERS) {
+ pr_warn("number of drivers exceeding static allocation\n");
+ break;
+ }
+
+ drv = &arm_idle_drivers[i];
+ drv->cpumask = kzalloc(cpumask_size(), GFP_KERNEL);
+ if (!drv->cpumask) {
+ ret = -ENOMEM;
+ break;
+ }
+ /*
+ * Force driver mask, arm_idle_init_driver()
+ * will tweak it by vetting idle states.
+ */
+ cpumask_copy(drv->cpumask, tmpmask);
+
+ ret = arm_idle_init_driver(drv);
+ if (ret) {
+ kfree(drv->cpumask);
+ break;
+ }
+ /*
+ * Remove the cpus that were part of the registered
+ * driver from the mask of cpus to be initialized
+ * and restart.
+ */
+ cpumask_andnot(tmpmask, tmpmask, drv->cpumask);
+ }
+ free_cpumask_var(tmpmask);
return ret;
}
device_initcall(arm_idle_init);
--
2.2.1
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