Re: [PATCH v7 0/5] OMAP: McBSP: Use register cache

[Peter Ujfalusi <peter.ujfalusi@nokia.com>]

Hello Janusz,

I'll try to go through the series.

On Wednesday 09 December 2009 22:24:13 ext Janusz Krzysztofik wrote:

> This could help for developing the McBSP context save/restore features, as
> well as solve the problem of possible register corruption, experienced on
> OMAP1510 based Amstrad Delta board at least.

For the context save/restore feature:
On OMAP3 this is not that straight forward IMHO.
OMAP3 has FIFO on the McBSP ports (1024+256, or 128 word long).
This buffer will be invalidated in case of OFF mode (or when context 
save/restore is needed).
So if we ever face with this situation, we need to make sure that the McBSP FIFO 
is empty prior to context save, so when we are restoring we are not going to 
loose any data.
Note also, that the McBSP FIFO can not be bypassed on OMAP3, which means that 
the FIFO is most of the time is kind of full.
Well, full in element mode, and mostly full in threshold mode.

In other words: on OMAP3 the context save/restore is not that simple as it is on 
OMAP1/2. We need to make sure that the FIFO is empty at the right moment, which 
can not be done with the current code, and to be honest, I can not see how it 
can be done, unless we branch out the OMAP3 related McBSP/DMA code, and leave 
the current implementation to support only OMAP1/2 class devices.

-- 
Péter
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html