Re: cx18: "missing audio" for analog recordings

[Mark Lord <mlord@pobox.com>]

On 16/04/10 08:59 AM, Andy Walls wrote:
..
> Accesses to those are orthognal to the rest of the cx18 driver,
> including the IRQ handler.  (I agree, its hard to follow things in the
> driver; it's very large.)
>
> Do note, however, that the audio standard detection microcontroller
> *does* write to the registers in 0x800-0x9ff *independent* of the linux
> cx18 driver.
>
> Locking with respect to the microcontroller would mean halting and
> restarting the microcontroller.  I don't know if that causes it to reset
> or not, and I do not know how it affects it's internal timers.
..

Since the problem really does behave like a "race condition" would behave,
I wonder if it could have something to do with how/when we modify any of
those registers which are shared with the microcontroller?

The cx18 driver *always* does read-modify-write (RMW) of 32-bits at at time,
even when just an "8-bit" register is being modified.

If the microcontroller is using/updating the other 24-bits of any of those
registers, then the cx18 driver's RMW will destroy values that the microcontroller
has written.

Is it possible to write only 8-bits, rather than having to do the RMW on 32-bits ?

Cheers
-- 
Mark Lord
Real-Time Remedies Inc.
mlord@pobox.com