Re: [RFC] pata_icside driver

Russell King
2007-04-09T08:44:59Z

On Mon, Apr 09, 2007 at 01:24:45AM -0700, Roland Dreier wrote:
> > Lets say that we want to do MW DMA mode 2. This has the minimum timing
> > of 70ns active, 25ns recovery, 120ns cycle time.
> >
> > When you quantise those figures using a clock period of 62.5ns (16MHz)
> > you end up with: 2 clocks active (2*62.5 > 70), 1 clock recovery
> > (1*62.5 > 25) and 2 clocks cycle (2*62.5 > 120).
> >
> > Last time I checked, active + recovery must always be equal to the cycle
> > time, and unless my math is failing me, 2 + 1 does not equal 2.
>
> Do you mean active + recovery must be less than or equal to the cycle
> time? Because 70ns + 25ns does not equal 120ns either...

Now that I've had some breakfast, yes.

In any case, active + recovery must never be greater than the cycle time.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/