Message-ID: <20240807180511.436bc1af@5400>
Date: Wed, 7 Aug 2024 18:05:11 -0400
From: Andres Salomon <dilinger@...ued.net>
To: Pali Rohár <pali@...nel.org>
Cc: Armin Wolf <W_Armin@....de>, linux-kernel@...r.kernel.org,
 platform-driver-x86@...r.kernel.org, Matthew Garrett <mjg59@...f.ucam.org>,
 Sebastian Reichel <sre@...nel.org>, Hans de Goede <hdegoede@...hat.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 linux-pm@...r.kernel.org, Dell.Client.Kernel@...l.com
Subject: Re: [PATCH v2 1/2] platform/x86:dell-laptop: Add knobs to change
 battery charge settings

On Wed, 7 Aug 2024 23:44:13 +0200
Pali Rohár <pali@...nel.org> wrote:

> On Wednesday 07 August 2024 17:28:32 Andres Salomon wrote:
> > On Fri, 26 Jul 2024 20:46:22 +0200
> > Armin Wolf <W_Armin@....de> wrote:
> >   
> > > Am 26.07.24 um 20:42 schrieb Armin Wolf:
> > >   
> > > > Am 26.07.24 um 06:25 schrieb Andres Salomon:
> > > >    
> > > >> On Fri, 26 Jul 2024 02:04:09 +0200
> > > >> Pali Rohár <pali@...nel.org> wrote:
> > > >>    
> > > >>> On Friday 26 July 2024 01:48:50 Armin Wolf wrote:    
> > > >>>> Am 26.07.24 um 00:15 schrieb Pali Rohár:
> > > >>>>    
> > > >>>>> On Thursday 25 July 2024 16:24:57 Andres Salomon wrote:    
> > > >>>>>> On Thu, 25 Jul 2024 01:01:58 +0200
> > > >>>>>> Pali Rohár <pali@...nel.org> wrote:
> > > >>>>>>    
> > > >>>>>>> On Wednesday 24 July 2024 18:23:18 Andres Salomon wrote:    
> > > >> [...]    
> > > >>>>>>> The issue here is: how to tell kernel that the particular
> > > >>>>>>> dell_battery_hook has to be bound with the primary battery?
> > > >>>>>>>    
> > > >>>>>> So from userspace, we've got the expectation that multiple batteries
> > > >>>>>> would show up as /sys/class/power_supply/BAT0,
> > > >>>>>> /sys/class/power_supply/BAT1,
> > > >>>>>> and so on.    
> > > >>>>> Yes, I hope so.
> > > >>>>>    
> > > >>>>>> The current BAT0 entry shows things like 'capacity' even without
> > > >>>>>> this
> > > >>>>>> patch, and we're just piggybacking off of that to add charge_type
> > > >>>>>> and
> > > >>>>>> other entries. So there shouldn't be any confusion there, agreed?    
> > > >>>>> I have not looked at the battery_hook_register() code yet (seems
> > > >>>>> that I
> > > >>>>> would have to properly read it and understand it). But does it
> > > >>>>> mean that
> > > >>>>> battery_hook_register() is adding hook just for "BAT0"?
> > > >>>>>
> > > >>>>> What I mean: cannot that hook be registered to "BAT1" too? Because if
> > > >>>>> yes then we should prevent it. Otherwise this hook which is for "Dell
> > > >>>>> Primary Battery" could be registered also for secondary battery
> > > >>>>> "BAT1".
> > > >>>>> (I hope that now it is more clear what I mean).    
> > > >>>> Hi,
> > > >>>>
> > > >>>> the battery hook is being registered to all ACPI batteries present
> > > >>>> on a given system,
> > > >>>> so you need to do some manual filtering when .add_battery() is called.    
> > > >>> Ok. So it means that the filtering based on the primary battery in
> > > >>> add_battery callback is needed.
> > > >>>    
> > > >> Thanks for the explanations. Seems simple enough to fix that, as some of
> > > >> the other drivers are checking battery->desc->name for "BAT0".
> > > >>
> > > >>
> > > >> One thing that I keep coming back to, and was reinforced as I looked at
> > > >> include/linux/power_supply.h; the generic power supply charge_type has
> > > >> values that are very close to Dells, but with different names. I could
> > > >> shoehorn them in, though, with the following mappings:
> > > >>
> > > >> POWER_SUPPLY_CHARGE_TYPE_FAST,         => "express" (aka ExpressCharge)
> > > >> POWER_SUPPLY_CHARGE_TYPE_STANDARD,     => "standard"
> > > >> POWER_SUPPLY_CHARGE_TYPE_ADAPTIVE,     => "adaptive"
> > > >> POWER_SUPPLY_CHARGE_TYPE_CUSTOM,       => "custom"
> > > >> POWER_SUPPLY_CHARGE_TYPE_LONGLIFE,     => "primarily_ac"
> > > >>
> > > >> The main difference is that Primarily AC is described and documented as
> > > >> slightly different than Long Life, but I suspect the result is roughly
> > > >> the same thing. And the naming "Fast" and "Long Life" wouldn't match the
> > > >> BIOS naming of "ExpressCharge" and "Primarily AC".
> > > >>
> > > >> Until now I've opted to match the BIOS naming, but I'm curious what
> > > >> others
> > > >> think before I send V3 of the patches.    
> > > >
> > > > I agree that POWER_SUPPLY_CHARGE_TYPE_FAST should be mapped the
> > > > ExpressCharge,
> > > > but i think that "primarily_ac" should become a official power supply
> > > > charging mode.
> > > >
> > > > The reason is that for example the wilco-charger driver also supports
> > > > such a charging mode
> > > > (currently reported as POWER_SUPPLY_CHARGE_TYPE_TRICKLE) and the
> > > > charging mode seems to be
> > > > both sufficiently different from
> > > > POWER_SUPPLY_CHARGE_TYPE_LONGLIFE/POWER_SUPPLY_CHARGE_TYPE_TRICKLE
> > > > and sufficiently generic to be supported by a wide array of devices.
> > > >
> > > > Thanks,
> > > > Armin Wolf
> > > >    
> > > I just read the documentation regarding the charge_type sysfs attribute and it states that:
> > > 
> > > Trickle:
> > > 	Extends battery lifespan, intended for users who
> > > 	primarily use their Chromebook while connected to AC.
> > > 
> > > So i think that "primarily_ac" should be mapped to POWER_SUPPLY_CHARGE_TYPE_TRICKLE.  
> > 
> > Do you think it's worth keeping around the sysfs-class-power-dell
> > file? At this point it's basically just documenting the slight naming
> > differences:
> > 
> > 
> >                 Standard:
> >                         Fully charge the battery at a moderate rate.
> >                 Fast:
> >                         Quickly charge the battery using fast-charge
> >                         technology. This is harder on the battery than
> >                         standard charging and may lower its lifespan.
> >                         The Dell BIOS calls this ExpressCharge™.
> >                 Trickle:
> >                         Users who primarily operate the system while
> >                         plugged into an external power source can extend
> >                         battery life with this mode. The Dell BIOS calls
> >                         this "Primarily AC Use".
> >                 Adaptive:
> >                         Automatically optimize battery charge rate based
> >                         on typical usage pattern.
> >                 Custom:
> >                         Use the charge_control_* properties to determine
> >                         when to start and stop charging. Advanced users
> >                         can use this to drastically extend battery life.
> > 
> >                 Access: Read, Write
> >                 Valid values:
> >                               "Standard", "Fast", "Trickle",
> >                               "Adaptive", "Custom"  
> 
> Another option could be to extend the description in sysfs-class-power
> file that "Trickle" covers "Dell's Primarily AC Use" and "Fast" covers
> "Dell's ExpressCharge".
> 
> So if somebody is going to implement charge_type for some other Laptop
> vendor then this information can help.

How's this?

@@ -378,8 +378,10 @@ Date:              July 2009
 Contact:       linux-pm@...r.kernel.org
 Description:
                Represents the type of charging currently being applied to the
-               battery. "Trickle", "Fast", and "Standard" all mean different
-               charging speeds. "Adaptive" means that the charger uses some
+               battery. "Fast" and "Standard" mean different charging speeds.
+               "Trickle" means a slow charging speed, or (depending on the
+               hardware) charging optimized for being mostly plugged into
+               wall power. "Adaptive" means that the charger uses some
                algorithm to adjust the charge rate dynamically, without
                any user configuration required. "Custom" means that the charger


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