Firewire and mobile cpu

[Max <dos...@ya...>]

Hello,

I am reporting here a bug with the use of my firewire harddisk enclosure on my linux system. My laptop has an athlon XP cpu with the "mobile" technology, this means that the clock of my cpu can vary depending on the demand. 
When the cpu is "on demand" mode (ie cpu clock can vary) and I try to write data to my harddrive connected via firewire, I get very quickly an I/O error.
On the other hand, when I fix my cpu clock (I use the max speed), there is no I/O error and the access read or write through the firewire never fails.
This problem was already exisiting with the "old" spb2 driver and still exists with the new driver.


Some more info about my config:
- kernel: 3.7.10-gentoo
- distri: gentoo
- my computer: Compaq presario 2120EU
- my firewire device is an IDE to firewire enclosure for 3,5' harddrives. The chip labeling is "PL3507 LF06018A".

- my firewire controller:
lspci | grep Fire
00:0c.0 FireWire (IEEE 1394): Texas Instruments TSB43AB21 IEEE-1394a-2000 Controller (PHY/Link)



As said, I can circonvent this problem easily, by setting my CPU to max speed, then plug my hardware enclosure and enjoy.

Additional information: 

-1- This enclosure was initialy not recognized when I was plugging it in. This problem was solved by changing the /lib/udev/scsi_id file permission from rwxr_xr_x to rw_r__r__ as reported in a previous post (post initially started by Peter Christy on 2012-02-20).

-2- My enclosure requires a "workarounds" option which reduces the firewire speed. Before I plug the firewire cable, the module is started as follow : modprobe firewire_ohci && modprobe firewire_sbp2 workarounds=0x1

Feel free to ask for more details if needed.

Best