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Message-ID: <CAJZ5v0jr4Z=ffm9E+eR7p7rQwbCWEP=YHxNbR9VAEwb8-3e3GA@mail.gmail.com>
Date: Tue, 13 Feb 2024 14:59:10 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>
Cc: linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
Daniel Lezcano <daniel.lezcano@...aro.org>, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Jiri Pirko <jiri@...nulli.us>, Johannes Berg <johannes@...solutions.net>,
Florian Westphal <fw@...len.de>, netdev@...r.kernel.org
Subject: Re: [PATCH v4 3/3] thermal: intel: hfi: Enable interface only when required
On Mon, Feb 12, 2024 at 5:16 PM Stanislaw Gruszka
<stanislaw.gruszka@...ux.intel.com> wrote:
>
> Enable and disable hardware feedback interface (HFI) when user space
> handler is present. For example, enable HFI, when intel-speed-select or
> Intel Low Power daemon is running and subscribing to thermal netlink
> events. When user space handlers exit or remove subscription for
> thermal netlink events, disable HFI.
>
> Summary of changes:
>
> - Register a thermal genetlink notifier
>
> - In the notifier, process THERMAL_NOTIFY_BIND and THERMAL_NOTIFY_UNBIND
> reason codes to count number of thermal event group netlink multicast
> clients. If thermal netlink group has any listener enable HFI on all
> packages. If there are no listener disable HFI on all packages.
>
> - When CPU is online, instead of blindly enabling HFI, check if
> the thermal netlink group has any listener. This will make sure that
> HFI is not enabled by default during boot time.
>
> - Actual processing to enable/disable matches what is done in
> suspend/resume callbacks. Create two functions hfi_do_enable()
> and hfi_do_disable(), which can be called from the netlink notifier
> callback and suspend/resume callbacks.
>
> Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka@...ux.intel.com>
> ---
> drivers/thermal/intel/intel_hfi.c | 95 +++++++++++++++++++++++++++----
> 1 file changed, 85 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c
> index 3b04c6ec4fca..5e1e2b5269b7 100644
> --- a/drivers/thermal/intel/intel_hfi.c
> +++ b/drivers/thermal/intel/intel_hfi.c
> @@ -159,6 +159,7 @@ struct hfi_cpu_info {
> static DEFINE_PER_CPU(struct hfi_cpu_info, hfi_cpu_info) = { .index = -1 };
>
> static int max_hfi_instances;
> +static int hfi_thermal_clients_num;
> static struct hfi_instance *hfi_instances;
>
> static struct hfi_features hfi_features;
> @@ -477,8 +478,11 @@ void intel_hfi_online(unsigned int cpu)
> enable:
> cpumask_set_cpu(cpu, hfi_instance->cpus);
>
> - /* Enable this HFI instance if this is its first online CPU. */
> - if (cpumask_weight(hfi_instance->cpus) == 1) {
> + /*
> + * Enable this HFI instance if this is its first online CPU and
> + * there are user-space clients of thermal events.
> + */
> + if (cpumask_weight(hfi_instance->cpus) == 1 && hfi_thermal_clients_num > 0) {
> hfi_set_hw_table(hfi_instance);
> hfi_enable();
> }
> @@ -573,28 +577,93 @@ static __init int hfi_parse_features(void)
> return 0;
> }
>
> -static void hfi_do_enable(void)
> +/*
> + * HFI enable/disable run in non-concurrent manner on boot CPU in syscore
> + * callbacks or under protection of hfi_instance_lock.
> + */
In the comment above I would say "If concurrency is not prevented by
other means, the HFI enable/disable routines must be called under
hfi_instance_lock." and I would retain the comments below (they don't
hurt IMO).
> +static void hfi_do_enable(void *ptr)
I would call this hfi_enable_instance().
> +{
> + struct hfi_instance *hfi_instance = ptr;
Why is this variable needed ro even useful? prt can be passed
directly to hfi_set_hw_table().
> +
> + hfi_set_hw_table(hfi_instance);
> + hfi_enable();
> +}
> +
> +static void hfi_do_disable(void *ptr)
And I'd call this hfi_disable_instance().
> +{
> + hfi_disable();
> +}
> +
> +static void hfi_syscore_resume(void)
> {
> /* This code runs only on the boot CPU. */
> struct hfi_cpu_info *info = &per_cpu(hfi_cpu_info, 0);
> struct hfi_instance *hfi_instance = info->hfi_instance;
>
> - /* No locking needed. There is no concurrency with CPU online. */
> - hfi_set_hw_table(hfi_instance);
> - hfi_enable();
> + if (hfi_thermal_clients_num > 0)
> + hfi_do_enable(hfi_instance);
> }
>
> -static int hfi_do_disable(void)
> +static int hfi_syscore_suspend(void)
> {
> - /* No locking needed. There is no concurrency with CPU offline. */
> hfi_disable();
>
> return 0;
> }
>
> static struct syscore_ops hfi_pm_ops = {
> - .resume = hfi_do_enable,
> - .suspend = hfi_do_disable,
> + .resume = hfi_syscore_resume,
> + .suspend = hfi_syscore_suspend,
> +};
> +
> +static int hfi_thermal_notify(struct notifier_block *nb, unsigned long state,
> + void *_notify)
> +{
> + struct thermal_genl_notify *notify = _notify;
> + struct hfi_instance *hfi_instance;
> + smp_call_func_t func;
> + unsigned int cpu;
> + int i;
> +
> + if (notify->mcgrp != THERMAL_GENL_EVENT_GROUP)
> + return NOTIFY_DONE;
> +
> + if (state != THERMAL_NOTIFY_BIND && state != THERMAL_NOTIFY_UNBIND)
> + return NOTIFY_DONE;
> +
> + mutex_lock(&hfi_instance_lock);
> +
> + switch (state) {
> + case THERMAL_NOTIFY_BIND:
> + hfi_thermal_clients_num++;
> + break;
> +
> + case THERMAL_NOTIFY_UNBIND:
> + hfi_thermal_clients_num--;
> + break;
> + }
> +
> + if (hfi_thermal_clients_num > 0)
> + func = hfi_do_enable;
> + else
> + func = hfi_do_disable;
> +
> + for (i = 0; i < max_hfi_instances; i++) {
> + hfi_instance = &hfi_instances[i];
> + if (cpumask_empty(hfi_instance->cpus))
> + continue;
> +
> + cpu = cpumask_any(hfi_instance->cpus);
> + smp_call_function_single(cpu, func, hfi_instance, true);
> + }
> +
> + mutex_unlock(&hfi_instance_lock);
So AFAICS, one instance can be enabled multiple times because of this.
I guess that's OK? In any case, it would be kind of nice to leave a
note regarding it somewhere here.
> +
> + return NOTIFY_OK;
> +}
> +
> +static struct notifier_block hfi_thermal_nb = {
> + .notifier_call = hfi_thermal_notify,
> };
>
> void __init intel_hfi_init(void)
> @@ -628,10 +697,16 @@ void __init intel_hfi_init(void)
> if (!hfi_updates_wq)
> goto err_nomem;
>
> + if (thermal_genl_register_notifier(&hfi_thermal_nb))
> + goto err_nl_notif;
Is it possible for any clients to be there before the notifier is
registered? If not, it would be good to add a comment about it.
> +
> register_syscore_ops(&hfi_pm_ops);
>
> return;
>
> +err_nl_notif:
> + destroy_workqueue(hfi_updates_wq);
> +
> err_nomem:
> for (j = 0; j < i; ++j) {
> hfi_instance = &hfi_instances[j];
> --
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