netdev - Re: [PATCH] wilc1000: Allow setting power_save before driver is initialized

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Date:   Wed, 15 Dec 2021 22:37:47 -0700
From:   David Mosberger-Tang <davidm@...uge.net>
To:     Ajay.Kathat@...rochip.com
Cc:     Claudiu.Beznea@...rochip.com, kvalo@...eaurora.org,
        davem@...emloft.net, kuba@...nel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] wilc1000: Allow setting power_save before driver is
 initialized

On Wed, 2021-12-15 at 13:01 +0000, Ajay.Kathat@...rochip.com wrote:
> On 13/12/21 02:50, David Mosberger-Tang wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > Unfortunately, this patch doesn't seem to be sufficient.  From what I
> > can tell, if power-save mode is turned on before a station is
> > associated with an access-point, there is no actual power savings.  If
> > I issue the command after the station is associated, it works perfectly
> > fine.
> > 
> > Ajay, does this make sense to you?
>   <snip>
> Power-save mode is allowed to be enabled irrespective of station 
> association state. Before association, the power consumption should be 
> less with PSM enabled compared to PSM disabled. The WLAN automatic power 
> save delivery gets enabled after the association with AP.
> 
> To check the power measurement before association,  test without 
> wpa_supplicant.
> 
> 
> Steps:
> - load the module
> - ifconfig wlan0 up
> - iw dev wlan0 set power_save off (check the pwr measurement after PS 
> mode disabled)
> - iw dev wlan0 set power_save on (check the pwr measurement after PS 
> mode enable)

It appears wpa_supplicant consistently renders PSM ineffective:

                                (current draw, 1 min avg):
------------------------------  --------------------------
- base case (no module loaded): 16.8 mA
- module loaded & PSM on      : 16.8 mA
- wpa_supplicant started      : 19.6 mA
- PSM on                      : 19.6 mA (no change)
- PSM off                     : 19.6 mA (no change)
- PSM on                      : 15.4 mA

What's strange is when I try this sequence a couple of times in a row,
the device gets into a state where after starting wpa_supplicant, no
amount of PSM on/off commands will get it to enter power-savings mode
any more.  When in that state, only removing wilc1000-spi.ko and adding
it back gets it out of that state.  A power-cycle does not.  Very
confusing.

  --david