igc: Add support for CBS offloading

Implement support for Credit-based shaper(CBS) Qdisc hardware
offload mode in the driver. There are two sets of IEEE802.1Qav
(CBS) HW logic in i225 controller and this patch supports
enabling them in the top two priority TX queues.

Driver implemented as recommended by Foxville External
Architecture Specification v0.993. Idleslope and Hi-credit are
the CBS tunable parameters for i225 NIC, programmed in TQAVCC
and TQAVHC registers respectively.

In-order for IEEE802.1Qav (CBS) algorithm to work as intended
and provide BW reservation CBS should be enabled in highest
priority queue first. If we enable CBS on any of low priority
queues, the traffic in high priority queue does not allow low
priority queue to be selected for transmission and bandwidth
reservation is not guaranteed.

Signed-off-by: Aravindhan Gunasekaran <aravindhan.gunasekaran@intel.com>
Signed-off-by: Mallikarjuna Chilakala <mallikarjuna.chilakala@intel.com>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

1 files changed, 103 insertions, 0 deletions

diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
index 2935d57c593d..0fce22de2ab8 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.c
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
@@ -18,6 +18,20 @@ static bool is_any_launchtime(struct igc_adapter *adapter)
 	return false;
 }
 
+static bool is_cbs_enabled(struct igc_adapter *adapter)
+{
+	int i;
+
+	for (i = 0; i < adapter->num_tx_queues; i++) {
+		struct igc_ring *ring = adapter->tx_ring[i];
+
+		if (ring->cbs_enable)
+			return true;
+	}
+
+	return false;
+}
+
 static unsigned int igc_tsn_new_flags(struct igc_adapter *adapter)
 {
 	unsigned int new_flags = adapter->flags & ~IGC_FLAG_TSN_ANY_ENABLED;
@@ -28,6 +42,9 @@ static unsigned int igc_tsn_new_flags(struct igc_adapter *adapter)
 	if (is_any_launchtime(adapter))
 		new_flags |= IGC_FLAG_TSN_QBV_ENABLED;
 
+	if (is_cbs_enabled(adapter))
+		new_flags |= IGC_FLAG_TSN_QAV_ENABLED;
+
 	return new_flags;
 }
 
@@ -87,6 +104,8 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
 	for (i = 0; i < adapter->num_tx_queues; i++) {
 		struct igc_ring *ring = adapter->tx_ring[i];
 		u32 txqctl = 0;
+		u16 cbs_value;
+		u32 tqavcc;
 
 		wr32(IGC_STQT(i), ring->start_time);
 		wr32(IGC_ENDQT(i), ring->end_time);
@@ -104,6 +123,90 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
 		if (ring->launchtime_enable)
 			txqctl |= IGC_TXQCTL_QUEUE_MODE_LAUNCHT;
 
+		/* Skip configuring CBS for Q2 and Q3 */
+		if (i > 1)
+			goto skip_cbs;
+
+		if (ring->cbs_enable) {
+			if (i == 0)
+				txqctl |= IGC_TXQCTL_QAV_SEL_CBS0;
+			else
+				txqctl |= IGC_TXQCTL_QAV_SEL_CBS1;
+
+			/* According to i225 datasheet section 7.5.2.7, we
+			 * should set the 'idleSlope' field from TQAVCC
+			 * register following the equation:
+			 *
+			 * value = link-speed   0x7736 * BW * 0.2
+			 *         ---------- *  -----------------         (E1)
+			 *          100Mbps            2.5
+			 *
+			 * Note that 'link-speed' is in Mbps.
+			 *
+			 * 'BW' is the percentage bandwidth out of full
+			 * link speed which can be found with the
+			 * following equation. Note that idleSlope here
+			 * is the parameter from this function
+			 * which is in kbps.
+			 *
+			 *     BW =     idleSlope
+			 *          -----------------                      (E2)
+			 *          link-speed * 1000
+			 *
+			 * That said, we can come up with a generic
+			 * equation to calculate the value we should set
+			 * it TQAVCC register by replacing 'BW' in E1 by E2.
+			 * The resulting equation is:
+			 *
+			 * value = link-speed * 0x7736 * idleSlope * 0.2
+			 *         -------------------------------------   (E3)
+			 *             100 * 2.5 * link-speed * 1000
+			 *
+			 * 'link-speed' is present in both sides of the
+			 * fraction so it is canceled out. The final
+			 * equation is the following:
+			 *
+			 *     value = idleSlope * 61036
+			 *             -----------------                   (E4)
+			 *                  2500000
+			 *
+			 * NOTE: For i225, given the above, we can see
+			 *       that idleslope is represented in
+			 *       40.959433 kbps units by the value at
+			 *       the TQAVCC register (2.5Gbps / 61036),
+			 *       which reduces the granularity for
+			 *       idleslope increments.
+			 *
+			 * In i225 controller, the sendSlope and loCredit
+			 * parameters from CBS are not configurable
+			 * by software so we don't do any
+			 * 'controller configuration' in respect to
+			 * these parameters.
+			 */
+			cbs_value = DIV_ROUND_UP_ULL(ring->idleslope
+						     * 61036ULL, 2500000);
+
+			tqavcc = rd32(IGC_TQAVCC(i));
+			tqavcc &= ~IGC_TQAVCC_IDLESLOPE_MASK;
+			tqavcc |= cbs_value | IGC_TQAVCC_KEEP_CREDITS;
+			wr32(IGC_TQAVCC(i), tqavcc);
+
+			wr32(IGC_TQAVHC(i),
+			     0x80000000 + ring->hicredit * 0x7735);
+		} else {
+			/* Disable any CBS for the queue */
+			txqctl &= ~(IGC_TXQCTL_QAV_SEL_MASK);
+
+			/* Set idleSlope to zero. */
+			tqavcc = rd32(IGC_TQAVCC(i));
+			tqavcc &= ~(IGC_TQAVCC_IDLESLOPE_MASK |
+				    IGC_TQAVCC_KEEP_CREDITS);
+			wr32(IGC_TQAVCC(i), tqavcc);
+
+			/* Set hiCredit to zero. */
+			wr32(IGC_TQAVHC(i), 0);
+		}
+skip_cbs:
 		wr32(IGC_TXQCTL(i), txqctl);
 	}