@@ -225,8 +225,11 @@ or in Section 3.4
:export:
-4. Example driver
------------------
+4. Examples
+-----------
+
+4.1 Example driver with EM registration
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The CPUFreq framework supports dedicated callback for registering
the EM for a given CPU(s) 'policy' object: cpufreq_driver::register_em().
@@ -280,3 +283,49 @@ EM framework::
39 static struct cpufreq_driver foo_cpufreq_driver = {
40 .register_em = foo_cpufreq_register_em,
41 };
+
+
+4.2 Example driver with EM modification
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+This section provides a simple example of a thermal driver modifying the EM.
+The driver implements a foo_mod_power() function to be provided to the
+EM framework. The driver is woken up periodically to check the temperature
+and modify the EM data if needed::
+
+ -> drivers/thermal/foo_thermal.c
+
+ 01 static int foo_mod_power(struct device *dev, unsigned long freq,
+ 02 unsigned long *power, void *priv)
+ 03 {
+ 04 struct foo_context *ctx = priv;
+ 05
+ 06 /* Estimate power for the given frequency and temperature */
+ 07 *power = foo_estimate_power(dev, freq, ctx->temperature);
+ 08 if (*power >= EM_MAX_POWER);
+ 09 return -EINVAL;
+ 10
+ 11 return 0;
+ 12 }
+ 13
+ 14 /*
+ 15 * Function called periodically to check the temperature and
+ 16 * update the EM if needed
+ 17 */
+ 18 static void foo_thermal_em_update(struct foo_context *ctx)
+ 19 {
+ 20 struct em_data_callback em_cb = EM_UPDATE_CB(mod_power);
+ 21 struct cpufreq_policy *policy = ctx->policy;
+ 22 struct device *cpu_dev;
+ 23
+ 24 cpu_dev = get_cpu_device(cpumask_first(policy->cpus));
+ 25
+ 26 ctx->temperature = foo_get_temp(cpu_dev, ctx);
+ 27 if (ctx->temperature < FOO_EM_UPDATE_TEMP_THRESHOLD)
+ 28 return;
+ 29
+ 30 /* Update EM for the CPUs' performance domain */
+ 31 ret = em_dev_update_perf_domain(cpu_dev, &em_cb, ctx);
+ 32 if (ret)
+ 33 pr_warn("foo_thermal: EM update failed\n");
+ 34 }
The Energy Model (EM) support runtime modifications. Add description with example driver code which updates EM. Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> --- Documentation/power/energy-model.rst | 53 ++++++++++++++++++++++++++-- 1 file changed, 51 insertions(+), 2 deletions(-)