[linux-dvb] Re: Latency ?

["Robert Schlabbach" <robert_s@gmx.net>]

From: "Rene Bartsch" <ml@bartschnet.de>
> Use "lspci -vvv" to get human readable values.
>
> The output for a SAA7146 should look like this:
> "Latency: 128 (3750ns min, 9500ns max)"

Hmm, how do they come up with these numbers? I thought these latencies were
in PCI clock cycles. Since the PCI clock is 33MHz, one cycle is 30ns. Thus,
128 cycles would be 3840ns, and 38 cycles would be 1140ns...?

> Min Latency is the minimum latency necessary for the SAA7146 to send all
> data off from his queue and max latency is the maximum latency until to
> be in turn again before the queue of the SAA7146 gets an overflow.

I don't understand :( What is the "minimum latency"? The "Latency: 128"
number above? And what does the "Minimum Grant" number mean?

more confused than enlightened,
--
Robert Schlabbach
e-mail: robert_s@gmx.net
Berlin, Germany



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