Messages in this thread Patch in this message | | | From | Lukasz Luba <> | Subject | [PATCH 16/17] Documentation: EM: Add example with driver modifying the EM | Date | Tue, 14 Mar 2023 10:33:56 +0000 |
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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(-)
diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst index 64c2462dc9a6..a6ceeeb72868 100644 --- a/Documentation/power/energy-model.rst +++ b/Documentation/power/energy-model.rst @@ -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 } -- 2.17.1
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