linux-kernel - Re: [PATCH] wifi: iwlwifi: mvm: enable thermal zone only when firmware is loaded

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Date:   Thu, 13 Jul 2023 11:41:00 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Harry Austen <hpausten@...tonmail.com>,
        linux-wireless@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Gregory Greenman <gregory.greenman@...el.com>,
        Kalle Valo <kvalo@...nel.org>,
        Johannes Berg <johannes.berg@...el.com>,
        Miri Korenblit <miriam.rachel.korenblit@...el.com>,
        Avraham Stern <avraham.stern@...el.com>,
        Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH] wifi: iwlwifi: mvm: enable thermal zone only when
 firmware is loaded

On 10/07/2023 12:47, Harry Austen wrote:
> In iwl_mvm_thermal_zone_register(), when registering a thermal zone, the
> thermal subsystem will evaluate its temperature.
> But iwl_mvm_tzone_get_temp() fails at this time because
> iwl_mvm_firmware_running() returns false.
> And that's why many users report that they see
> "thermal thermal_zoneX: failed to read out thermal zone (-61)"
> message during wifi driver probing.
> 
> This patch attempts to fix this by delaying enabling of the thermal zone
> until after the firmware has been loaded/initialized. It also gets
> disabled when going into suspend.

Thanks for taking care of this bug.

The thermal zone will be accessible from userspace and can be enabled 
manually. The resulting temperature read error will be the same in this 
case.

IMO, it is cleaner to actually [un]register the thermal zone when the 
firmware is [un]loaded

> Signed-off-by: Harry Austen <hpausten@...tonmail.com>
> ---
>   .../net/wireless/intel/iwlwifi/mvm/mac80211.c  | 18 ++++++++++++++++++
>   drivers/net/wireless/intel/iwlwifi/mvm/tt.c    |  9 +--------
>   2 files changed, 19 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c b/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
> index ce7905faa08f..a47d29a64dd4 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c
> @@ -1187,6 +1187,17 @@ int iwl_mvm_mac_start(struct ieee80211_hw *hw)
> 
>   	mutex_unlock(&mvm->mutex);
> 
> +#ifdef CONFIG_THERMAL
> +	/* Needs to be done outside of mutex guarded section to prevent deadlock, since enabling
> +	 * the thermal zone calls the .get_temp() callback, which attempts to acquire the mutex.
> +	 */
> +	if (!ret) {
> +		ret = thermal_zone_device_enable(mvm->tz_device.tzone);
> +		if (ret)
> +			IWL_DEBUG_TEMP(mvm, "Failed to enable thermal zone (err = %d)\n", ret);
> +	}
> +#endif
> +
>   	iwl_mvm_mei_set_sw_rfkill_state(mvm);
> 
>   	return ret;
> @@ -1282,6 +1293,7 @@ void __iwl_mvm_mac_stop(struct iwl_mvm *mvm)
>   void iwl_mvm_mac_stop(struct ieee80211_hw *hw)
>   {
>   	struct iwl_mvm *mvm = IWL_MAC80211_GET_MVM(hw);
> +	int ret;
> 
>   	flush_work(&mvm->async_handlers_wk);
>   	flush_work(&mvm->add_stream_wk);
> @@ -1307,6 +1319,12 @@ void iwl_mvm_mac_stop(struct ieee80211_hw *hw)
> 
>   	iwl_mvm_mei_set_sw_rfkill_state(mvm);
> 
> +#ifdef CONFIG_THERMAL
> +	ret = thermal_zone_device_disable(mvm->tz_device.tzone);
> +	if (ret)
> +		IWL_DEBUG_TEMP(mvm, "Failed to disable thermal zone (err = %d)\n", ret);
> +#endif
> +
>   	mutex_lock(&mvm->mutex);
>   	__iwl_mvm_mac_stop(mvm);
>   	mutex_unlock(&mvm->mutex);
> diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/tt.c b/drivers/net/wireless/intel/iwlwifi/mvm/tt.c
> index 157e96fa23c1..964d2d011c6b 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mvm/tt.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mvm/tt.c
> @@ -680,7 +680,7 @@ static  struct thermal_zone_device_ops tzone_ops = {
> 
>   static void iwl_mvm_thermal_zone_register(struct iwl_mvm *mvm)
>   {
> -	int i, ret;
> +	int i;
>   	char name[16];
>   	static atomic_t counter = ATOMIC_INIT(0);
> 
> @@ -707,13 +707,6 @@ static void iwl_mvm_thermal_zone_register(struct iwl_mvm *mvm)
>   		return;
>   	}
> 
> -	ret = thermal_zone_device_enable(mvm->tz_device.tzone);
> -	if (ret) {
> -		IWL_DEBUG_TEMP(mvm, "Failed to enable thermal zone\n");
> -		thermal_zone_device_unregister(mvm->tz_device.tzone);
> -		return;
> -	}
> -
>   	/* 0 is a valid temperature,
>   	 * so initialize the array with S16_MIN which invalid temperature
>   	 */
> --
> 2.41.0
> 
> 

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