tc: Add support for configuring the taprio scheduler

This traffic scheduler allows traffic classes states (transmission
allowed/not allowed, in the simplest case) to be scheduled, according
to a pre-generated time sequence. This is the basis of the IEEE
802.1Qbv specification.

Example configuration:

tc qdisc replace dev enp3s0 parent root handle 100 taprio \
          num_tc 3 \
	  map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \
	  queues 1@0 1@1 2@2 \
	  base-time 1528743495910289987 \
	  sched-entry S 01 300000 \
	  sched-entry S 02 300000 \
	  sched-entry S 04 300000 \
	  clockid CLOCK_TAI

The configuration format is similar to mqprio. The main difference is
the presence of a schedule, built by multiple "sched-entry"
definitions, each entry has the following format:

     sched-entry <CMD> <GATE MASK> <INTERVAL>

The only supported <CMD> is "S", which means "SetGateStates",
following the IEEE 802.1Qbv-2015 definition (Table 8-6). <GATE MASK>
is a bitmask where each bit is a associated with a traffic class, so
bit 0 (the least significant bit) being "on" means that traffic class
0 is "active" for that schedule entry. <INTERVAL> is a time duration
in nanoseconds that specifies for how long that state defined by <CMD>
and <GATE MASK> should be held before moving to the next entry.

This schedule is circular, that is, after the last entry is executed
it starts from the first one, indefinitely.

The other parameters can be defined as follows:

 - base-time: specifies the instant when the schedule starts, if
  'base-time' is a time in the past, the schedule will start at

 	      base-time + (N * cycle-time)

   where N is the smallest integer so the resulting time is greater
   than "now", and "cycle-time" is the sum of all the intervals of the
   entries in the schedule;

 - clockid: specifies the reference clock to be used;

The parameters should be similar to what the IEEE 802.1Q family of
specification defines.

Signed-off-by: Vinicius Costa Gomes <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

include/uapi/linux/pkt_sched.h

@@ -1084,4 +1084,50 @@ enum {
 	CAKE_ATM_MAX
 };
 
+
+/* TAPRIO */
+enum {
+	TC_TAPRIO_CMD_SET_GATES = 0x00,
+	TC_TAPRIO_CMD_SET_AND_HOLD = 0x01,
+	TC_TAPRIO_CMD_SET_AND_RELEASE = 0x02,
+};
+
+enum {
+	TCA_TAPRIO_SCHED_ENTRY_UNSPEC,
+	TCA_TAPRIO_SCHED_ENTRY_INDEX, /* u32 */
+	TCA_TAPRIO_SCHED_ENTRY_CMD, /* u8 */
+	TCA_TAPRIO_SCHED_ENTRY_GATE_MASK, /* u32 */
+	TCA_TAPRIO_SCHED_ENTRY_INTERVAL, /* u32 */
+	__TCA_TAPRIO_SCHED_ENTRY_MAX,
+};
+#define TCA_TAPRIO_SCHED_ENTRY_MAX (__TCA_TAPRIO_SCHED_ENTRY_MAX - 1)
+
+/* The format for schedule entry list is:
+ * [TCA_TAPRIO_SCHED_ENTRY_LIST]
+ *   [TCA_TAPRIO_SCHED_ENTRY]
+ *     [TCA_TAPRIO_SCHED_ENTRY_CMD]
+ *     [TCA_TAPRIO_SCHED_ENTRY_GATES]
+ *     [TCA_TAPRIO_SCHED_ENTRY_INTERVAL]
+ */
+enum {
+	TCA_TAPRIO_SCHED_UNSPEC,
+	TCA_TAPRIO_SCHED_ENTRY,
+	__TCA_TAPRIO_SCHED_MAX,
+};
+
+#define TCA_TAPRIO_SCHED_MAX (__TCA_TAPRIO_SCHED_MAX - 1)
+
+enum {
+	TCA_TAPRIO_ATTR_UNSPEC,
+	TCA_TAPRIO_ATTR_PRIOMAP, /* struct tc_mqprio_qopt */
+	TCA_TAPRIO_ATTR_SCHED_ENTRY_LIST, /* nested of entry */
+	TCA_TAPRIO_ATTR_SCHED_BASE_TIME, /* s64 */
+	TCA_TAPRIO_ATTR_SCHED_SINGLE_ENTRY, /* single entry */
+	TCA_TAPRIO_ATTR_SCHED_CLOCKID, /* s32 */
+	TCA_TAPRIO_PAD,
+	__TCA_TAPRIO_ATTR_MAX,
+};
+
+#define TCA_TAPRIO_ATTR_MAX (__TCA_TAPRIO_ATTR_MAX - 1)
+
 #endif

net/sched/Kconfig

@@ -194,6 +194,17 @@ config NET_SCH_ETF
 	  To compile this code as a module, choose M here: the
 	  module will be called sch_etf.
 
+config NET_SCH_TAPRIO
+	tristate "Time Aware Priority (taprio) Scheduler"
+	help
+	  Say Y here if you want to use the Time Aware Priority (taprio) packet
+	  scheduling algorithm.
+
+	  See the top of <file:net/sched/sch_taprio.c> for more details.
+
+	  To compile this code as a module, choose M here: the
+	  module will be called sch_taprio.
+
 config NET_SCH_GRED
 	tristate "Generic Random Early Detection (GRED)"
 	---help---

net/sched/Makefile

@@ -57,6 +57,7 @@ obj-$(CONFIG_NET_SCH_HHF)	+= sch_hhf.o
 obj-$(CONFIG_NET_SCH_PIE)	+= sch_pie.o
 obj-$(CONFIG_NET_SCH_CBS)	+= sch_cbs.o
 obj-$(CONFIG_NET_SCH_ETF)	+= sch_etf.o
+obj-$(CONFIG_NET_SCH_TAPRIO)	+= sch_taprio.o
 
 obj-$(CONFIG_NET_CLS_U32)	+= cls_u32.o
 obj-$(CONFIG_NET_CLS_ROUTE4)	+= cls_route.o