Re: [PATCH v3 5/8] net: dsa: hellcreek: Add TAPRIO offloading support

On Sat Aug 22 2020, Vladimir Oltean wrote:

Hi Kurt,

On Thu, Aug 20, 2020 at 10:11:15AM +0200, Kurt Kanzenbach wrote:

quoted

The switch has support for the 802.1Qbv Time Aware Shaper (TAS). Traffic
schedules may be configured individually on each front port. Each port has eight
egress queues. The traffic is mapped to a traffic class respectively via the PCP
field of a VLAN tagged frame.

The TAPRIO Qdisc already implements that. Therefore, this interface can simply
be reused. Add .port_setup_tc() accordingly.

The activation of a schedule on a port is split into two parts:

 * Programming the necessary gate control list (GCL)
 * Setup hrtimer for starting the schedule

The hardware supports starting a schedule up to eight seconds in the future. The
TAPRIO interface provides an absolute base time. Therefore, hrtimers are
leveraged.

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
---
 drivers/net/dsa/hirschmann/hellcreek.c | 294 +++++++++++++++++++++++++
 drivers/net/dsa/hirschmann/hellcreek.h |  21 ++
 2 files changed, 315 insertions(+)

diff --git a/drivers/net/dsa/hirschmann/hellcreek.c b/drivers/net/dsa/hirschmann/hellcreek.c
index 745ca60342b4..e5b54f42c635 100644
--- a/drivers/net/dsa/hirschmann/hellcreek.c
+++ b/drivers/net/dsa/hirschmann/hellcreek.c

@@ -22,7 +22,9 @@
 #include <linux/spinlock.h>
 #include <linux/delay.h>
 #include <linux/ktime.h>
+#include <linux/time.h>
 #include <net/dsa.h>
+#include <net/pkt_sched.h>
 
 #include "hellcreek.h"
 #include "hellcreek_ptp.h"

@@ -153,6 +155,15 @@ static void hellcreek_select_vlan(struct hellcreek *hellcreek, int vid,
 	hellcreek_write(hellcreek, val, HR_VIDCFG);
 }
 
+static void hellcreek_select_tgd(struct hellcreek *hellcreek, int port)
+{
+	u16 val = 0;
+
+	val |= port << TR_TGDSEL_TDGSEL_SHIFT;
+
+	hellcreek_write(hellcreek, val, TR_TGDSEL);
+}
+
 static int hellcreek_wait_until_ready(struct hellcreek *hellcreek)
 {
 	u16 val;

@@ -958,6 +969,24 @@ static void __hellcreek_setup_tc_identity_mapping(struct hellcreek *hellcreek)
 	}
 }
 
+static void hellcreek_setup_tc_mapping(struct hellcreek *hellcreek,
+				       struct net_device *netdev)
+{
+	int i, j;
+
+	/* Setup mapping between traffic classes and port queues. */
+	for (i = 0; i < netdev_get_num_tc(netdev); ++i) {
+		for (j = 0; j < netdev->tc_to_txq[i].count; ++j) {
+			const int queue = j + netdev->tc_to_txq[i].offset;
+
+			hellcreek_select_prio(hellcreek, i);
+			hellcreek_write(hellcreek,
+					queue << HR_PRTCCFG_PCP_TC_MAP_SHIFT,
+					HR_PRTCCFG);
+		}
+	}
+}

What other driver have you seen that does this?

Probably none.

With TAPRIO traffic classes and the mapping to queues can be
configured. The switch can also map traffic classes. That sounded like a
good match to me.

Thanks,
Kurt