Trying Linus' latest (as of this morning) out on a PXA255 platform with a WM9705 codec reveals a number of problems:
1. when suspend occurs, we turn the AC97 link off by setting the GCR_ACLINK_OFF bit, and stopping the functional units clock.
On resume, we reconfigure the pins and re-enable the clock. Unfortunately, this results in GCR being left with zeros, and GSR remains all zeros, and the codec is inaccessible, with lots of warnings from the read/write functions scrolling by:
pxa2xx_ac97_write: write error (ac97_reg=118 GSR=0x0) pxa2xx_ac97_read: read error (ac97_reg=118 GSR=0x0) pxa2xx_ac97_read: read error (ac97_reg=118 GSR=0x0) ...
Setting GCR to '2' (to release cold reset) using devmem2 starts things moving again, shutting up this warning.
2. maybe as a result of the above problem, the wm9705 touchscreen driver doesn't reinitialize, causing loss of touchscreen. Unbinding and re-binding the driver restores the touchscreen, but with a very long lag between touching the screen and it being registered.
I bring (2) up because I notice that the resume actions in (1) are deferred. Given that codecs have shared functions (such as touchscreens) need to access the codec from their own resume functions, how can this deferral be safe?
Liam - this problem has been noticed on a NetbookPro (I'm sure you remember that platform...)