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

[Harry Austen <hpausten@protonmail.com>]

On Sun Jul 16, 2023 at 2:45 PM BST, Zhang, Rui wrote:
> On Thu, 2023-07-13 at 11:41 +0200, Daniel Lezcano wrote:
> > 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
>
> Currently, I see that the mode is checked only in
> __thermal_zone_device_update().
>
> should we limit the userspace access for disabled thermal zone? For
> example, return failure when reading 'temp' sysfs attribute.

Ah okay thanks for checking. Yes, agree that is probably a more sensible behaviour.

>
> >  and can be enabled
> > manually.
>
> maybe we should have a .change_mode() callback and return failure when
> enabling the thermal zone with wifi firmware unloaded.
>
> >  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
>
> Austen,
> may I know how often is this wifi firmware loaded/unloaded?

Personally, I have only ever seen the firmware loaded once on boot and never unloaded. That was the reason for my patch;
I was trying to reduce the number of kernel warning/error log messages on my system during boot. As far as I can tell,
the ieee80211_ops stop() callback is only called in drv_stop(), which for example can be called via ieee80211_suspend().

>
> thanks,
> rui
> >
> > > Signed-off-by: Harry Austen <hpausten@protonmail.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
> > >
> > >
> >

Thanks for the review! :)
Harry