linux-kernel - Re: Power management

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Message-ID: <20191104150648.GG28764@mit.edu>
Date:   Mon, 4 Nov 2019 10:06:48 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Tom Cook <tom.k.cook@...il.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: Power management - HP 15-ds0502na

On Mon, Nov 04, 2019 at 02:32:30PM +0000, Tom Cook wrote:
> s2idle sort of works - the thing appears to go to sleep and wake up
> okay - but the power savings are not really enough to make it
> worthwhile.  Putting it into s2idle state and putting it in a bag
> results in a very hot laptop - and of course that makes battery life
> not great.  I'm guessing this is the Ryzen 7 CPU idle states not being
> very well supported?

Actually, it's probably because one of the device drives isn't
properly putting that particular device into a low power state.  When
I was trying to make s2idle work on the XPS 13, there was needed patch
to make the SATA AHCI controller go into a lower power state.  This
was a patch which the Dell folks had gotten into their special
"Optimized for Dell laptops" Ubuntu kernel that was running into
resistance upstream.  I *think* that patch finally made it upstream,
but to be honest, I haven't been keeping track since I decided "life
was too short to fight and make s2idle work".

I probably should see if newer kernels have fixed some of these
issues, since the XPS13 is currently my preferred laptop, and I worry
that future models will drop suspend-to-ram, since Windows 10 is using
s2idle, and so the incentive for laptop manufacturers to support
suspend-to-ram is almost non-existent, especially now that Windows XP
and Windows 7 have moved to the great deprecation bitbucket in the
sky....  :-(

      	     	   	       		    - Ted