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Subject: Re: [PATCH v2 4/4] ath10k: Enable sta idle power save
To: Sebastian Gottschall <s.gottschall@dd-wrt.com>,
        Kalle Valo <kvalo@codeaurora.org>, govinds@codeaurora.org
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Cc: pillair@codeaurora.org, linux-wireless@vger.kernel.org,
        ath10k@lists.infradead.org
From: Arend van Spriel <arend.vanspriel@broadcom.com>
Message-ID: <5AD9A1DF.6060007@broadcom.com> (sfid-20180420_101642_153991_0BE5244F)
Date: Fri, 20 Apr 2018 10:16:31 +0200
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On 4/20/2018 9:21 AM, Sebastian Gottschall wrote:
>
>>> Yes this is WIFI chip set level power-save(based on idleness) and not
>>> related to protocol power save. FW will turn off/scale down the
>>> resources(clock/rails) based on opportunity(when ever idle mode is
>>> detected). This power save is mostly done in disconnected state. I am
>>> not really sure when framework/user-space triggers power-save
>>> config(iw dev <devname> set power_save on/off). Then doing this from
>>> user-space will be unnecessarily toggling this config or may not be
>>> setting at disconnected state.
>> I think that 'set power_save' commands affects struct
>> ieee80211_bss_conf::ps parameter and I don't think it should be used in
>> this case. We already have ath10k_config_ps() for 802.11 level of power
>> saving.
>>
>> Arend again proposed runtime-pm with which I'm not very familiar. But
>> why would we want to disable this? Doesn't it make sense to have this
>> feature always enabled to save power? wcn3990 is a chip for a mobile
>> device anyway.
> it might be made for mobile devices but who knows how it is used by the
> market.

Reading the explanation above it does not make sense to use runtime-pm. 
That would only come into play if the host driver would actually control 
the resources being turned off/scaled down.

So this is purely reducing power-consumption of the chip. However, it 
would be good to know the consequences in terms of responsiveness to 
firmware commands for instance when requesting a scan operation. Another 
thing to consider is to provide user-space with possibility to change 
this configuration (maybe through debugfs?).

Regards,
Arend