Denis 'GNUtoo' Carikli писал 04.10.2012 15:07:
On Thu, 04 Oct 2012 14:53:08 +0400 Peter Zotov whitequark@whitequark.org wrote:
Denis 'GNUtoo' Carikli писал 04.10.2012 14:26:
On Thu, 4 Oct 2012 00:32:48 +0200 Peter Stuge peter@stuge.se wrote:
John Case wrote:
the real trick I am interested is isolating (or at least controlling) the interaction between the baseband processor and
the
application processor. Using a computer with a USB dongle
gives
me
that control ... would I have that same level of control if we had free software running on the baseband processor, or is
there
still additional bleeding possible simpy by virtue of being built into the computer ?
In a smartphone it's almost not possible to distinguish the "computer" from the "GSM modem" anymore, because of how the hardware is constructed, so yes.
In some yes, in some no... it depend on how the smartphone was designed:
On one end some smartphones (openmoko GTA02,golden delicious GTA04), the baseband is isolated(tough on GTA04 it has access to a GPS with no antenna(so it can't work)) . And on the other end there are smartphones with qualcomm System on a chip...where the modem and the CPU are
in
a single chip: The modem part has the audio DSP connected to it, the GPS. And the baseband uses shared RAM memory and shared NAND(if I remember well)... And I'm not sure but maybe the baseband is even needed for booting the main CPU...
There are also systems in between like the galaxy S/Neuxs S that uses shared memory but do not have other problems...
In addition to the above, there are some phones where baseband is completely submissive to the AP, namely Galaxy SII. Basically it's exactly the same as the USB dongle situation, but the dongle is integrated on the phone's PCB.
Did you check what the modem transport was(shared memory, high speed serial etc...)?
Denis.
HSIC. It's basically USB but with a slightly altered physical layer to acommodate the unusual topology. http://www.synopsys.com/dw/dwtb/hsic_usb2_device/hsic_usb2_device.html
There is no shared memory or, in fact, any other connections between BP and interfaces of the phone. Audio is transferred via the same USB, for example.
GPS technically has some relation with the BP, I'm not absolutely sure which precisely, but you can a) upload reference SiRF firmware to the GPS, thus rendering any changes Samsung put to the latter void and b) AP controls !RESET pins of both GPS and BP. It's trivial to not allow both to run simultaneously.
baseband-devel@lists.osmocom.org
-
Peter Zotov