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SubjectRe: [PATCH v8 09/13] cpufreq: amd-pstate: add driver working mode switch support
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On 12/19/2022 00:40, Perry Yuan wrote:
> From: Perry Yuan <Perry.Yuan@amd.com>
>
> While amd-pstate driver was loaded with specific driver mode, it will
> need to check which mode is enabled for the pstate driver,add this sysfs
> entry to show the current status
>
> $ cat /sys/devices/system/cpu/amd-pstate/status
> active
>
> Meanwhile, user can switch the pstate driver mode with writing mode
> string to sysfs entry as below.
>
> Enable passive mode:
> $ sudo bash -c "echo passive > /sys/devices/system/cpu/amd-pstate/status"
>
> Enable active mode (EPP driver mode):
> $ sudo bash -c "echo active > /sys/devices/system/cpu/amd-pstate/status"
>
> Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
> ---
> drivers/cpufreq/amd-pstate.c | 128 +++++++++++++++++++++++++++++++++++
> 1 file changed, 128 insertions(+)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index fc12d35bc7bd..e8996e937e63 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -64,6 +64,7 @@ static struct cpufreq_driver amd_pstate_driver;
> static struct cpufreq_driver amd_pstate_epp_driver;
> static struct amd_cpudata **all_cpu_data;
> static int cppc_state = AMD_PSTATE_DISABLE;
> +struct kobject *amd_pstate_kobj;
>
> static inline int get_mode_idx_from_str(const char *str, size_t size)
> {
> @@ -90,6 +91,8 @@ static struct amd_pstate_params global_params;
> static DEFINE_MUTEX(amd_pstate_limits_lock);
> static DEFINE_MUTEX(amd_pstate_driver_lock);
>
> +static DEFINE_SPINLOCK(cppc_notify_lock);
> +
> static s16 amd_pstate_get_epp(struct amd_cpudata *cpudata, u64 cppc_req_cached)
> {
> u64 epp;
> @@ -644,6 +647,8 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
> policy->driver_data = cpudata;
>
> amd_pstate_boost_init(cpudata);
> + if (!default_pstate_driver->adjust_perf)
> + default_pstate_driver->adjust_perf = amd_pstate_adjust_perf;
>
> return 0;
>
> @@ -784,12 +789,106 @@ static ssize_t show_energy_performance_preference(
> return sysfs_emit(buf, "%s\n", energy_perf_strings[preference]);
> }
>
> +static ssize_t amd_pstate_show_status(char *buf)
> +{
> + if (!default_pstate_driver)
> + return sysfs_emit(buf, "off\n");
> +
> + return sysfs_emit(buf, "%s\n", default_pstate_driver == &amd_pstate_epp_driver ?
> + "active" : "passive");

Didn't you introduce const strings for this in an earlier patch from the
series?

How about using the indices from that rather than hardcoding /another/
string.

Also keep in mind guided mode will be coming so
"case ? true_val : false_val"

So perhaps you should just have have some if cases so you don't have to
switch the whole thing out.

> +}
> +
> +static void amd_pstate_driver_cleanup(void)
> +{
> + unsigned int cpu;
> +
> + cpus_read_lock();
> + for_each_online_cpu(cpu) {
> + if (all_cpu_data[cpu]) {
> + spin_lock(&cppc_notify_lock);
> + kfree(all_cpu_data[cpu]);
> + WRITE_ONCE(all_cpu_data[cpu], NULL);
> + spin_unlock(&cppc_notify_lock);
> + }
> + }
> + cpus_read_unlock();
> +
> + default_pstate_driver = NULL;
> +}
> +
> +static int amd_pstate_update_status(const char *buf, size_t size)
> +{

Rather than looking at each size for each case, how about you just look
at the boundaries once? Something like this:

if (size > 7 || size < 3)
return -EINVAL;

Then you should be able to run strncmp for each of your cases.

> + if (size == 3 && !strncmp(buf, "off", size)) {

This seems like another case that would be good to use the const strings
you already introduced for state machine checking.

> + if (!default_pstate_driver)
> + return -EINVAL;
> +
> + if (cppc_state == AMD_PSTATE_ACTIVE)
> + return -EBUSY;
> +
> + cpufreq_unregister_driver(default_pstate_driver);
> + amd_pstate_driver_cleanup();
> + return 0;
> + }
> +
> + if (size == 6 && !strncmp(buf, "active", size)) {

This seems like another case that would be good to use the const strings
you already introduced for state machine checking.

> + if (default_pstate_driver) {
> + if (default_pstate_driver == &amd_pstate_epp_driver)
> + return 0;
> + cpufreq_unregister_driver(default_pstate_driver);
> + default_pstate_driver = &amd_pstate_epp_driver;
> + cppc_state = AMD_PSTATE_ACTIVE;
> + }
> +
> + return cpufreq_register_driver(default_pstate_driver);
> + }
> +
> + if (size == 7 && !strncmp(buf, "passive", size)) {

This seems like another case that would be good to use the const strings
you already introduced for state machine checking.

> + if (default_pstate_driver) {
> + if (default_pstate_driver == &amd_pstate_driver)
> + return 0;
> + cpufreq_unregister_driver(default_pstate_driver);
> + cppc_state = AMD_PSTATE_PASSIVE;
> + default_pstate_driver = &amd_pstate_driver;
> + }
> +
> + return cpufreq_register_driver(default_pstate_driver);
> + }
> +
> + return -EINVAL;
> +}
> +
> +static ssize_t show_status(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + ssize_t ret;
> +
> + mutex_lock(&amd_pstate_driver_lock);
> + ret = amd_pstate_show_status(buf);
> + mutex_unlock(&amd_pstate_driver_lock);
> +
> + return ret;
> +}
> +
> +static ssize_t store_status(struct kobject *a, struct kobj_attribute *b,
> + const char *buf, size_t count)
> +{
> + char *p = memchr(buf, '\n', count);
> + int ret;
> +
> + mutex_lock(&amd_pstate_driver_lock);
> + ret = amd_pstate_update_status(buf, p ? p - buf : count);
> + mutex_unlock(&amd_pstate_driver_lock);
> +
> + return ret < 0 ? ret : count;
> +}
> +
> cpufreq_freq_attr_ro(amd_pstate_max_freq);
> cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
>
> cpufreq_freq_attr_ro(amd_pstate_highest_perf);
> cpufreq_freq_attr_rw(energy_performance_preference);
> cpufreq_freq_attr_ro(energy_performance_available_preferences);
> +define_one_global_rw(status);
>
> static struct freq_attr *amd_pstate_attr[] = {
> &amd_pstate_max_freq,
> @@ -807,6 +906,15 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
> NULL,
> };
>
> +static struct attribute *pstate_global_attributes[] = {
> + &status.attr,
> + NULL
> +};
> +
> +static const struct attribute_group amd_pstate_global_attr_group = {
> + .attrs = pstate_global_attributes,
> +};
> +
> static inline void update_boost_state(void)
> {
> u64 misc_en;
> @@ -1228,6 +1336,26 @@ static int __init amd_pstate_init(void)
> if (ret)
> pr_err("failed to register with return %d\n", ret);
>
> + amd_pstate_kobj = kobject_create_and_add("amd-pstate", &cpu_subsys.dev_root->kobj);
> + if (!amd_pstate_kobj) {
> + ret = -EINVAL;
> + pr_err("global sysfs registration failed.\n");
> + goto kobject_free;
> + }
> +
> + ret = sysfs_create_group(amd_pstate_kobj, &amd_pstate_global_attr_group);
> + if (ret) {
> + pr_err("sysfs attribute export failed with error %d.\n", ret);
> + goto global_attr_free;
> + }
> +
> + return ret;
> +
> +global_attr_free:
> + kobject_put(amd_pstate_kobj);
> +kobject_free:
> + kfree(cpudata);
> + cpufreq_unregister_driver(default_pstate_driver);
> return ret;
> }
> device_initcall(amd_pstate_init);

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