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Message-ID: <20070409084447.GB28366@flint.arm.linux.org.uk> Date: Mon, 9 Apr 2007 09:44:48 +0100 From: Russell King <rmk+lkml@....linux.org.uk> To: Roland Dreier <rdreier@...co.com> Cc: Alan Cox <alan@...rguk.ukuu.org.uk>, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Jeff Garzik <jgarzik@...ox.com> Subject: Re: [RFC] pata_icside driver 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/ maintainer of: - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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