Re: [PATCH v2 net-next 1/1] net: dsa: hellcreek: Add TAPRIO offloading support

On Tue Jan 19 2021, Jakub Kicinski wrote:

On Sat, 16 Jan 2021 13:49:22 +0100 Kurt Kanzenbach wrote:

quoted

+	if (base_time_ns - current_ns < (s64)8 * NSEC_PER_SEC)
+		return true;
+
+	return false;

nit:
	return base_time_ns - current_ns < (s64)8 * NSEC_PER_SEC;

Sure.

quoted

+	/* Schedule periodic schedule check */
+	schedule_delayed_work(&hellcreek_port->schedule_work,
+			      HELLCREEK_SCHEDULE_PERIOD);

Why schedule this work every 2 seconds rather than scheduling it
$start_time - 8 sec + epsilon?

The two seconds are taken from the programming guide. That's why I used
it.

The PTP frequency starts to matter for large deltas. In theory the
rescheduling period can be increased [1]. Should I adjust it? 

quoted

+static bool hellcreek_validate_schedule(struct hellcreek *hellcreek,
+					struct tc_taprio_qopt_offload *schedule)
+{
+	/* Does this hellcreek version support Qbv in hardware? */
+	if (!hellcreek->pdata->qbv_support)
+		return false;
+
+	/* cycle time can only be 32bit */
+	if (schedule->cycle_time > (u32)-1)
+		return false;
+
+	/* cycle time extension is not supported */
+	if (schedule->cycle_time_extension)
+		return false;

What's the story with entries[i].command? I see most drivers validate
the command is what they expect.

Good catch! I'll add the validation.

Thanks,
Kurt

[1] - https://lkml.kernel.org/netdev/20200901144755.jd2wnmweywwvkwvl@skbuf/