Re: activate DMA of QCI (PXA320)

[Vitus Jensen <vjensen@xxxxxx>]

Hi Judith,

On Thu, 9 Jul 2009, Judith Baumgarten wrote:

> I try to use the QCI of PXA320, but can't start the DMA. Coming from
> an PXA270 I know there was a DMA-Enable-bit in CICR0, but it's gone in
> PXA320. The descriptor registers are programmed, so I think, it just
> have to start.

Did you program the special DMA channel dedicated to QCI?


> Does somebody know how to get it to work?

Just enable the QCI interface.  Whenever a byte is received from the 
camera a request will be send to the DMA channel.  Automatically, without 
further enable bits.

Please be aware that you can't stop the DMA (the DMA stop bit isn't 
supported in the DMA channel dedicated to QCI) and you can't use QCI 
without DMA transfers to occurr.  So in my driver I enable QCI only in 
vsync gaps and append a "loop" to the DMA chain for the case when my vsync 
isr is too slow to react to vsync.  But you can't read vsync state from 
QCI without enabling it so either switch the MFP or additionally wire the 
vsync line to another GPIO.

Or you could stay with PXA270 which has a much QCI in my opinion =:->

Vitus

-- 
Vitus Jensen, Hannover, Germany, Universe (current)
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