Re: snd-nm256: hard lockup on every second module load after powerup

[Takashi Iwai <tiwai@suse.de>]

At Sun, 26 Mar 2006 07:45:42 +0200,
Christian Trefzer wrote:
> 
> Hi folks,
> 
> I have this really old Dell Latitude CPiA here containing the dreaded
> neomagic combined audio/video chipset, and observe some hard lockup
> sometimes, which is not supposed to be anything special wrt. other
> people with similar laptops having the same trouble. The only regularity
> I noticed was that after completely removing power to the machine, the
> sound driver can be loaded without locking the thing hard. Any further
> attempt, eg. rmmod and insmod or reboot with alsasound startup script,
> will result in a dead machine. Every time. Cut the power, and next time
> it will survive - exactly once.
> 
> Now this chip is a NM2200 / 256AV, and I already did some reading in the
> alsa driver source code, but adding printk()s all over the place just
> showed that it does not lock up during init_chip() or poking at the
> registers during ac97_reset(), but shortly after the latter, approx.
> half a second or so - it might still be a consequence thereof.
> 
> My basic idea is, with the device being entirely undocumented (to hell
> with all hardware vendors who don't even release specs after the devices
> are not even sold anymore, by the way), that the code is missing a
> proper device reset, and trying to re-init some parts just kill the
> machine. Cutting the power really is not that nice as a workaround. I'd
> love to try something along the lines of saving the device's state as a
> whole, and before reloading the module, restore that state again. The
> difference between before and after should somehow give a clue about the
> proper reset procedure - or so I hope.
> 
> Unfortunately I failed with my previous attempts to modify the driver
> appropriately. Now that it's basically back to formula, I wanted to ask
> whether there is a possibility to read and write back whole parts of
> memory directly from/to the device, or if I should rather store each and
> every register somewhere I can later restore it from, one by one. I'd
> even prefer userspace, and am currently experimenting with pcidump.
> 
> 
> Any hints would be greatly appreciated! Thanks a bunch,

Try 2.6.16-git tree.  Some patches for this problem are there.


Takashi