Hi there

quoted text
> -----Original Message-----
> From: Haavard Skinnemoen [mailto:haavard.skinnemoen@atmel.com]
> Sent: Friday, August 01, 2008 6:50 AM
> 
> Haavard Skinnemoen <haavard.skinnemoen@atmel.com> wrote:
> >  		spi_writel(as, RNCR, 0);
> >  		spi_writel(as, TNCR, 0);
 
quoted text
> These writes are also completely pointless -- RNCR is zeroed 
> automatically after it gets shifted into RCR.

While looking at the patch yesterday I was thinking the same thing.  Now it
bugs me that this observation didn't occur when I was working on this
problem.  Maybe the code symmetry makes it look "correct".

quoted text
> Actually, I think the real bug happens right here

You're probably correct.  A race condition that intermittently clears a
pending interrupt fits the observed symptom.

 
quoted text
> As for the overruns, I'm beginning to suspect that the only way to get
> rid of those and still maintain a reasonable transfer rate is to use
> bounce buffers in faster RAM (e.g. on-chip SRAM).

For my at91sam9260 board, I eliminated one cause of SPI overruns by lowering
the interrupt priorities of the six USARTs (default was 5, changed to 4)
relative to the two SPI controllers (default is 5).  The test I used for
this issue is 'ls -lR' on the flash filesystem.

Regards -- Gerard

--
unsubscribe notice
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/