Re: [Ksummit-discuss] [TECH TOPIC] mobile phones

[Sebastian Reichel <sebastian.reichel@collabora.co.uk>]

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Hi,

On Tue, Jun 27, 2017 at 12:18:36AM -0700, Tony Lindgren wrote:
> > Does ofonod support the modems in an useful way?
> 
> No idea, I've only used qmicli so far.

There is a qmi plugin for ofono, but I also just used qmi utils [0]
so far.

[0] https://packages.debian.org/sid/libqmi-utils

> > Is GSM connected directly to the audio, or does it need real-time
> > task, similar to N900?
> 
> The audio mixer is on CPCAP PMIC, and I think mdm6600 modem audio needs
> help from the Linux kernel on the applications processor as it probably
> goes to it first then to CPCAP PMIC. I guess it's possible that mdm6600
> audio goes directly to CPCAP PMIC too.
> 
> I believe LTE modem is connected to the second SPI interface on the
> CPCAP PMIC and can use it directly for audio depending on how Linux
> kernel configures the PMIC secondary interface device access. What
> seems to be a similar PMIC for the CPCAP internal devices is documented
> in MC13783UG.pdf on NXP site so that might be worth looking at for
> the audio overview.

GSM audio is connected to the audio codec using digital audio
interface. The audio data normally does not flow through the CPU
(but as far as I can see it could be routed that way, if desired).
So no need for any low latency stuff on CPU side. Actually no need
to do anything except for proper setup of modem & audio codec :)

> > It looks like nice machine. OTOH N950 looks like a nice machine, too,
> > and N900 is actually nicer because of the resistive touch, battery,
> > and friendly bootloader...
> 
> Sure, my n950 just got so worn down I was afraid I don't have any
> replacement. And we need some kind of potential community upgrade for
> n900/n9/n950 anyways while waiting for better devices :)

I think Droid4 and N950 are almost on par regarding to mainline
support. N900 is has better hardware support in mainline - actually
once your camera bits land it reached basically 100% with just the
GPU missing. OTOH it's quite slow and has only 256MB of memory.

-- Sebastian

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