linux-kernel - Re: [PATCH] wilc1000: Allow setting power

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Date:   Thu, 23 Dec 2021 10:08:00 -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 Thu, 2021-12-23 at 14:02 +0000, Ajay.Kathat@...rochip.com wrote:
> 
> I verified with wpa_supplicant and it seems the power save mode is 
> working fine. Tested multiple times with wpa_supplicant running. I 
> didn't observe any issue in entering or exiting the power-save mode with 
> wpa_supplicant.
> 
> Try to verify without wpa_supplicant in your setup to observe if we are 
> seeing this same results in that case.

It doesn't help me if it works without wpa_supplicant.  I need a
reliable way to have power-savings mode in effect when using
wpa_supplicant.

> With wpa_supplicant, the current consumption is less when PS mode is 
> enabled but it would be more compared to without wpa_supplicant.

That's not what I'm talking about though.  The problem is that it seems
to be rather erratic whether issuing the iw power_save command makes a
difference in power-consumption.

I fixed my setup so I can directly measure power consumed rather than
just current (power factor matters).  Again, this is for the entire
device (not just WILC1000).

What I find that when power-saving mode is working as expected, the
device uses an average of 1.1W.  When power-saving mode is not working,
power consumption is about 1.4W, or about 300mW higher.

I tried again *without* the patch applied and, as expected, the patch
doesn't really affect this behavior.

After playing with this for a while, I think I found two sequences that
reliably reproduce the difference.

First, on a freshly booted system and with wilc1000-spi autoloaded by
the kernel, try this sequence (copy & paste the commands):

   /usr/sbin/wpa_supplicant -Bs -iwlan0 -c/etc/wpa_supplicant.conf
   sleep 10
   iw dev wlan0 set power_save on

The above yields a power consumption of 1.4W reliably.  The "sleep 10"
doesn't matter here; the behavior is the same with or without it.  I
tried waiting up to 120 seconds with no difference.

Second, on a freshly booted system and with wilc1000-spi autoloaded by
the kernel, try this sequence (copy & paste the commands):

   /usr/sbin/wpa_supplicant -Bs -iwlan0 -c/etc/wpa_supplicant.conf
   sleep 10
   rmmod wilc1000-spi
   modprobe wilc1000-spi
   sleep 10
   iw dev wlan0 set power_save on

The above yields a power consumption of 1.1W reliably.

Can you reproduce this, or, if not, share the power consumption you see
for the two cases?

  --david