On Mon, 18 Feb 2008 11:57:56 -0800 David Brownell <[EMAIL PROTECTED]> wrote:
> On Monday 18 February 2008, Atsushi Nemoto wrote: > > IIRC the clock state follows > > CSRn.CPOL just before the real transfer. > > No ... clock state should be valid *before* chipselect goes > active. So I'm thinking the patch from Haavard is likely > the right change. Hopefully it is... > > CLK ______________________|~|___|~~~|___|~~~|___|~~~|___ > > ... and at T1 CPOL is changed?? That's wrong. There should > never be a partial clock period while a chipselect is active. > While it's inactive, sure -- no chip should care. ...but what I'm afraid of is that since we're using GPIO chipselects, the controller may _think_ that no chip is selected and change the clock polarity just before it would pull the chipselect low if we were using automatic chipselects... If that's the case, it would be a bit strange if it actually helped to initialize all the CSRn registers, but it would also offer us a nice workaround... Atsushi, do you by any chance have debugging enabled? That would explain the long delay from CS activation to the change of clock polarity. Compared to printk() the DMA setup takes almost no time at all. If you can confirm that my patch helps, I think that's the one we want in mainline. Haavard ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ spi-devel-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/spi-devel-general
