[maemo-developers] [maemo-developers] examining n800 kernel

[From: Frantisek Dufka]

Hi,

I've been looking at the n800 kernel source in bora repository to figure 
out what n800 is like comparing to the n770. Here is a summary of some 
things I found. As I don't have the device I may be wrong with something 
that could be easily verified.

kernel is 2.6.18-omap1 - everybody probably knows that :-)

MMC/SD

4 bit data bus seems to be used only for SD cards, omap2 maximum speed 
is now set to 48Mhz (was 24Mhz for omap1 reduced to 12Mhz for N770). 
There are no high speed MMCmobile/plus (or high speed SD) patches 
applied so I guess SD cards run at 24Mhz, MMC at 16Mhz. There are also 
no patches for wider bus width (4 bit) for MMCmobile. SDHC cards are not 
supported too. As there are patches floating on the net for all these 
things (done mostly by Philip Langdale http://intr.overt.org/blog/) 
future looks promising :-) Oh, BTW multiblock writes _are_ enabled in 
this kernel.

Video

similar setup like N770 but hopefully improved (finally no memory 
bicycle but proper bus?). The external videochips seems to be from epson 
too, not 472 but 475 (or 4 in early prototypes?) called Blizzard and 
Hailstorm. Difference seems to be bigger memory buffer (1280K) that 
allows 24 bits in 800x480 instead of 16 on N770. See also
http://www.erd.epson.com/index.php?option=com_docman&task=cat_view&gid=68&Itemid=40
So the framebuffer is still external but handled by something different. 
OMAP1 uses something called SOSSI, OMAP2 calls it RFBI (remote frame 
buffer ...) Interesting is that omap framebuffer driver now contains 
code for synchronization on vblank and preventing tearing effect. It is 
both in omapfb/blizzard/rfbi code for n800 and also for 
omapfb/hwa472/sossi code for n770! Lets hope some variant of this kernel 
will go into some future n770 firmware. If not we can try to backport it 
for mplayer. from the code it looks like the pin from 472 chip 
signalling horizontal or vertical blank perion is indeed connected to 
something and checked (?) inside sossi driver. The is still no support 
for display rotation feature of the epson chip.

Both IVA and MBX are a bit of a mystery to me. Probably another ones to 
the bag with jazzelle technology so it won't feel alone there unused :-)
http://focus.ti.com/general/docs/wtbu/wtbugencontent.tsp?templateId=6123&navigationId=12719&contentId=27458

USB

Seems to be 2.0, capable of high speed mode (480MBits), chip is TUSB6010 
by TI. No usb host mode is compiled in the kernel. Usb host mode support 
was also removed from initfs (usb booting) so this may look bad.

BT

Was already discussed, see the bt headsed thread - Bluecore4 CSR chip 
capable of BT2.0, driver is called hci_h4p in drivers/bluetooth/hci_h4p 
(not present in mainline kernel?).

WI-FI

seems to be same chip as in (newer) N770 devices (?), similar firmware 
blobs (3825.arm, 3826.arm) probably newer versions. Hopefully the speed 
will be better that those 500KB/s on N770 thanks to rest of the system.

Audio

Alsa compiled in, OMAP24xx EAC driver, mixer support, PCM should be 
handled by DSP.

Feel free to correct or expand if something is wrong/missing.

Frantisek