netdev - Re: [PATCH 3/3] thermal: intel: hfi: Enable interface only when required

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Date: Wed, 31 Jan 2024 17:48:08 -0800
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
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>,
	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>,
	netdev@...r.kernel.org
Subject: Re: [PATCH 3/3] thermal: intel: hfi: Enable interface only when
 required

On Wed, Jan 31, 2024 at 01:05:35PM +0100, Stanislaw Gruszka 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.

I'd rephrase as:

Enable and disable HFI when a user space handler is running and listening
to thermal netlink events (e.g., intel-speed-select, Intel Low Power
daemon). When the user space handlers exit or remove subscription, disable
HFI.

> 
> Summary of changes:
> 
> - When CPU is online, instead of blindly enabling HFI by calling
> hfi_enable(), check if the thermal netlink group has any listener.
> This will make sure that HFI is not enabled by default during boot
> time.

s/by calling hfi_enable()//

> 
> - Register a netlink notifier.
> 
> - In the notifier process reason code NETLINK_CHANGE and

s/notifier/notifier,/

> NETLINK_URELEASE. If thermal netlink group has any listener enable
> HFI on all packages. If there are no listener disable HFI on all
> packages.
> 
> - Actual processing to enable/disable matches what is done in
> suspend/resume callbacks. So, create two functions hfi_do_enable()

s/So,//

> 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 | 82 +++++++++++++++++++++++++++----
>  1 file changed, 73 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/thermal/intel/intel_hfi.c b/drivers/thermal/intel/intel_hfi.c
> index 3b04c6ec4fca..50601f75f6dc 100644
> --- a/drivers/thermal/intel/intel_hfi.c
> +++ b/drivers/thermal/intel/intel_hfi.c
> @@ -30,6 +30,7 @@
>  #include <linux/kernel.h>
>  #include <linux/math.h>
>  #include <linux/mutex.h>
> +#include <linux/netlink.h>
>  #include <linux/percpu-defs.h>
>  #include <linux/printk.h>
>  #include <linux/processor.h>
> @@ -480,7 +481,8 @@ void intel_hfi_online(unsigned int cpu)
>  	/* Enable this HFI instance if this is its first online CPU. */
>  	if (cpumask_weight(hfi_instance->cpus) == 1) {
>  		hfi_set_hw_table(hfi_instance);
> -		hfi_enable();
> +		if (thermal_group_has_listeners(THERMAL_GENL_EVENT_GROUP))
> +			hfi_enable();

You could avoid the extra level of indentation if you did:
	if (cpumask_weight() == 1 && has_listeners())

You would need to also update the comment.

My two cents.