EHCI isoc scheduling

[Paul Zimmerman <Paul.Zimmerman@xxxxxxxxxxxx>]

Hi Alan,

Can you give me a clue about this code in ehci-sched.c/iso_stream_schedule()?

		/* For high speed devices, allow scheduling within the
		 * isochronous scheduling threshold.  For full speed devices
		 * and Intel PCI-based controllers, don't (work around for
		 * Intel ICH9 bug).
		 */
		if (!stream->highspeed && ehci->fs_i_thresh)
			next = now + ehci->i_thresh;
		else
			next = now;

Why does the driver allow scheduling within the threshold? I though the whole
point of the threshold value in the HCCPARAMS register was to tell the driver
the earliest time when it is safe to do scheduling.

Plus, the code doesn't seem to be doing what the comment says for the ICH9
workaround case (ehci->fs_i_thresh = 1). It seems the && should be an ||
instead.

The driver seems to be violating the EHCI spec here. Or am I misunderstanding
what the code is doing?

Thanks.

-- 
Paul

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