[Xperia Z2 Android Development] Entropy512:
No you didn't. There isn't a single mention of HVDCP anywhere in that file, and no discussion whatsoever of QC2.0. A few of the parameters in there might be relevant to QC2.0, but they're generic and have applied to many Qualcomm PMICs including ones that pre-date QC2.0. Also, when Sony added their "special" changes to qpnp-charger, they didn't update the documentation - there's no mention there of the SOMC step charging items. (actually, I could swear I saw them somewhere in Documentation, they might be in a different file.)

Oh yeah a github link is a hell of a lot easier for people than a box.com link - especially since many firewalls block storage providers like box.com but not github - https://github.com/sonyxperiadev/ke...on/devicetree/bindings/power/qpnp-charger.txt

It took you months to figure this out? I found it within a day or two of starting, talked to Alin, got the scoop on why the Docomo variant had it and others didn't, and decided it was a bad idea to turn it on. See the date of https://gerrit.omnirom.org/#/c/12811/ - I did my QC2.0 research back in March. I still haven't actually merged it into Omni's codebase because I want to make absolutely sure our thermmanager config is up to snuff. That's just turning on HVDCP and not bumping up the charge current (which I am NOT doing...)

As far as the Nexus 6 handling much higher charge currents - Same capacity battery as the Z2 in a MUCH larger device (and I am fairly certain, significantly larger battery). It seems to me that supporting high current charging properly requires different battery optimizations that compromise capacity. (I'm having a friend run some tests on a Nexus 6 - If it does the CC/CV transition for 0.66C charge current at higher than 65% SOC, that's clear evidence its battery has been optimized to accept higher charging currents.) Edit: From my Engadget link below: "he company figures that it can increase the thickness of the electrodes to improve battery life (by as much as 28Wh/L, according to one chart) without negative effect thanks to the softer charge." - So yes, construction of the battery does indeed allow tradeoff of capacity for other properties of the battery for a given battery volume. (Although, if you read the comments on the Engadget article, the quote about thickening the electrodes is likely wrong. However see A. Dennis' comment specifically - Moving electrodes closer together improves power density (ability to accept a rapid charge/discharge rapidly) but at the cost of reduced energy density (capacity).

There's also the fact that while the Nexus 6 battery is officially "non-replaceable" - The reality is that a service center (or even a user) can do a battery swap fairly easily - I don't have time to dig up the link, but look at iFixit's teardown. The battery is really easy to get at. Meanwhile, I would never trust the waterproofing of any Z-series device that had its battery replaced, even by a service center. Waterproofing makes for a wide variety of battery management challenges not present in the Nexus 6.

Oh, and before anyone digs up my old Infuse kernel which had a stepcharging implementation that took it to a shade over 0.5C (stock was well below 0.5C) - That device had a user-replacable battery.

No it doesn't entirely reside kernel-side - the hvdcp negotitation binary is in /system. No binary, no HVDCP.

And you still insist that Docomo having it on the Z3 means it's safe. You're clearly new to Android, otherwise you'd know that the worst entities in the industry are carriers with a long track record of screwing up devices. AT&T's wacky touchscreen in the I777. AT&T's battery-life-ruining/storage-thrashing apps on the Xperia TL. Docomo burning people's hands by deploying W-CDMA before they had figured out how to make efficient transmit power amplifiers for W-CDMA handsets. Yeah, you're basing your "it's safe" arguments on the actions of a carrier that prematurely deployed technology that overheated handsets around 12 years ago - http://www.3g.co.uk/PR/Jan2003/4800.htm - http://michiyonakamoto.ulitzer.com/node/40911

As to your marketing conspiracy theories - https://www.qualcomm.com/news/snapdragon/2014/06/04/quick-charge-20-has-arrived and https://www.qualcomm.com/news/relea...ology-available-japan-through-ntt-docomo-2014 - Note a common theme here? Docomo forced ALL of their handset vendors to support QC2.0, whether it was appropriate for the hardware or not. It's kind of like how AT&T customers had the Galaxy S2 S**trocket shoved down their throats only a month after the Galaxy S2 (SGH-I777) was released - AT&T forced all of their OEMs to provide LTE-capable handsets, and for the Galaxy S2 generation, that meant a crippled Snapdragon S3-based turd of a device. As much as I hate Exynos from a software development perspective, the Snapdragon S3 was worse in every way except for LTE support.

Whatever source you're using that actually claims that charging slower than 0.5C is unhealthy is full of ****.

And I was fully aware you increased charge current from 0.5C to around 0.66-0.68C - I read the kernel source patches. You still are constantly confusing numbers since the 60% I've been talking about is the step charging threshold, not the charge current in ratio of C.

The Z3c's step charging threshold, along with the Docomo Z3's, is 60% state of charge - https://github.com/sonyxperiadev/ke...ot/dts/msm8974pro-ac-shinano_leo_dcm.dtsi#L79

The problem is, 60% is too close to the 65% threshold at which point the Z2's battery transitions from CC to CV charging according to someone who posted data from a charge cycle on G+ - http://imgur.com/Njdsyua . Compare this to Apple's stepcharging patent from four years ago - http://www.engadget.com/2011/02/20/apple-patent-application-points-to-denser-batteries-improved-ch/

Given that the Z3 hits CC/CV transition for 0.5C current at around 78% SOC, it likely hits the 0.68C CC/CV transition pretty close to the 65% SOC that the Z2 does.

The Z2 QC2.0 implementation is, based on that graph, clearly NOT performing step charging (and the kernel source confirms this - no stepping in https://github.com/AndroPlus-org/an...mmit/0603873691f74e8e7306065b7e57d303b2991b47 ) - so you're clearly stressing the battery more. You keep on saying "oh we never exceeded temperature threshold X so it's fine". There's no magic threshold at which your battery instantly breaks - the hotter it is and the faster you charge it, the faster it will degrade. Look at the Engadget link above. Look at the bottom graph of cycle life... Note the significant reduction in cycle life for "traditional" charging vs. step charging (Approximately 75-82% capacity remaining after 300 cycles for "traditional" charging at 0.45C vs. 90% remaining for stepcharging)? This setup is using traditional charging in nearly all, if not all operating regimes, but at the C-rate Apple used for the high-current "first step".

In Apple's patent, they used voltage thresholds and not state-of-charge thresholds. Also, they implemented stepcharging somewhat differently - Instead of instantly changing to a new current setting at each step, they set a maximum voltage for each step. When that step went into CV mode and current went below that of the next step, they'd increase voltage to the next step. In Apple's configuration in the patent:

0.65C up to 4.0v

0.45C up to 4.1v

0.25C up to 4.2v

(Note: That's an older battery chemisty that has a CV limit of 4.2v - Newer high-energy-density batteries such as that in the Z2/Z3 have a max of 4.35v. Either way - all patches in play here are running 0.6C or higher all the way up to 4.35v. Again, look at the cycle life impact this has in the lower graph of that link.)

Actually, high-voltage (9v or more) charging makes cable quality far less relevant. That's the real benefit of QC2.0 on the Z3, and the one part of QC2.0 that I believe is safe on the Z3.

Since the SO-03F has different hardware than other Xperia Z2 variants (download the manual at https://www.nttdocomo.co.jp/english/support/trouble/manual/download/so03f/download.html and note that the SO-03F has a TV receiver not present in international devices, whoever was claiming the Docomo and international Z2s were the same hardware number was very very wrong), I would not trust the non-Docomo Z2s to have charger circuit support components (capacitors, diodes, etc.) to be rated for the increased input voltage.