Re: [Ipodlinux-devel] new ipod, etc

[Bernard L. <le...@bo...>]

Hi Dani,

Its great to see some revived interested in the project.  Unfortunately
my time is fairly limited but I'm willing to try and help out where ever
possible.

Reviving the initrd may indeed be a good plan - unfortunately I don't
have any of the old code hanging around.  It should be quite easy to get
going though as there are a number of examples with the other uClinux
targets using it.  The full uClinux "distribution" build has a mechanism
to automatically build the disk image.

>From what I remember there actually isn't much more required than whats
in the head-arm-ipod.S.  Once you enable the compile option I think the
rest of the code just switches on...

As for the serial stuff doing it in the kernel may be kinda hard...
however the ipod serial driver is already working so in theory if you
just started up a console on the right tty line it would all work!  I
assume the g2 hardware has one of the UARTs IN line connected up for the
remote control.  I would assume the g3 has the OUT line for the same
UART connected up (the other UART is used for the piezo).  Unfortunately
I have no idea what pin on the connector might be used (is there a
dissection out there somewhere??).

Other thoughts; yes the CPU is speced to go up to at least 90MHz. 
Cranking it up doesn't really improve performance as the problem is more
that the memory is not fast enough.  The 96KB of on chip ram _is_ fast
enough and that does help.  The problem is getting balance right between
putting code/data in the fast ram and then splitting the workload
between the two cpu cores.

The SRAM starts at 0x28000000 the on board ram is 0x40000000.

Sorry I don't have a mbox archive and it doesnt seem the mailing list
software will spit one out...

cheers,
bern.

On Mon, 2003-10-20 at 18:53, PALFFY Daniel wrote:
> Hi,
> 
> It seems like the ipodlinux development has slowed down a bit last
> months... I think it would be nice to accelerate it, since I'll reveive my
> new g3 ipod this week.
> 
> I really want to get the kernel running on the new ipods and i will try to
> do it to my best knowledge, but since I haven't done much low level kernel
> programming, any help would be appreciated.
> 
> I think the first two steps would be to revive initrd support and to look
> if one of the new remote pins was connected to a serial output (I can
> easily imagine a bigger remote with an LCD display as a future accessory).
> 
> About the initrd part: Bern, do you have any of the early versions running
> from initrd? The CVS tree at sourceforge doesn't seem to contain anything
> except the stub in head-arm-ipod.S.
> 
> About the serial ports: What should I try to get some 01010101 out on the
> serial port that I can look for with a scope? If I could boot to an initrd
> it would be easy, but I haven't ever tried kernel space serial
> programming... Or should I write a short assembly routine and boot to it
> directly?
> 
> And some other thoughts:
> 
> The current code sets the processor speed to 75MHz, but, according to the
> specs it should support 90. This increment should help somewhat in vorbis
> and mp3 decoding.
> 
> Also, the 96Kb of on-chip SRAM could help. The current development of
> tremor to support DSPs is trying to reduce memory footprint - so if we
> could squeeze as much of the critical code into SRAM as possible might
> help a lot, especially because the main memory seems slooowwww if it only
> has a 16 bit bus. The slight overhead in CPU cycles should not matter,
> someone on the tremor development list claimed that a 30-40 MHz ARM should
> be able to decode vorbis if it had enough fast RAM. By the way, I couldn't
> find much about the memory map of the iPods. Where is the SRAM memory
> located?
> 
> Thanks in advance for any help.
> 
> PS: does anyone have the archives of the list in mailbox format? It would
> be nice to be able to read it offline...
> 
> --
> Dani
> 			...and Linux for all.
> 
> 
> 
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