Date:	Sun, 12 Jun 2016 00:22:16 +0200
From:	Henrik Austad <henrik@...tad.us>
To:	linux-kernel@...r.kernel.org
Cc:	linux-media@...r.kernel.org, alsa-devel@...r.kernel.org,
	linux-netdev@...r.kernel.org, henrk@...tad.us,
	Henrik Austad <henrik@...tad.us>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	intel-wired-lan@...ts.osuosl.org,
	"David S. Miller" <davem@...emloft.net>,
	Henrik Austad <haustad@...co.com>
Subject: [very-RFC 3/8] Adding TSN-driver to Intel I210 controller

This adds support for loading the igb.ko module with tsn
capabilities. This requires a 2-step approach. First enabling TSN in
.config, then load the module with use_tsn=1.

Once enabled and loaded, the controller will be placed in "Qav-mode"
which is when the credit-based shaper is available, 3 of the queues are
removed from regular traffic, max payload is set to 1522 octets (no
jumboframes allowed).

It dumps the registers of interest before and after, so this clutters
kern.log a bit. In time this will be reduced / tied to the debug-param
for the module.

Note: currently this driver is *not* stable, it is still a work in
progress.

Cc: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc: intel-wired-lan@...ts.osuosl.org
Cc: "David S. Miller" <davem@...emloft.net>
Signed-off-by: Henrik Austad <haustad@...co.com>
---
 drivers/net/ethernet/intel/Kconfig        |  18 ++
 drivers/net/ethernet/intel/igb/Makefile   |   2 +-
 drivers/net/ethernet/intel/igb/igb.h      |  19 ++
 drivers/net/ethernet/intel/igb/igb_main.c |  10 +-
 drivers/net/ethernet/intel/igb/igb_tsn.c  | 396 ++++++++++++++++++++++++++++++
 5 files changed, 443 insertions(+), 2 deletions(-)
 create mode 100644 drivers/net/ethernet/intel/igb/igb_tsn.c

diff --git a/drivers/net/ethernet/intel/Kconfig b/drivers/net/ethernet/intel/Kconfig
index 714bd10..8e620a9 100644
--- a/drivers/net/ethernet/intel/Kconfig
+++ b/drivers/net/ethernet/intel/Kconfig
@@ -99,6 +99,24 @@ config IGB
 	  To compile this driver as a module, choose M here. The module
 	  will be called igb.
 
+config IGB_TSN
+       tristate "TSN Support for Intel(R) 82575/82576 i210 Network Controller"
+       depends on IGB && TSN
+	---help---
+	  This driver supports TSN (AVB) on Intel I210 network controllers.
+
+	  When enabled, it will allow the module to be loaded with
+	  "use_tsn" which will initialize the controller to A/V-mode
+	  instead of legacy-mode. This will take 3 of the tx-queues and
+	  place them in 802.1Q QoS mode and enable the credit-based
+	  shaper for 2 of the queues.
+
+	  If built with this option, but not loaded with use_tsn, the
+	  only difference is a slightly larger module, no extra
+	  code paths are called.
+
+	  If unsure, say No
+
 config IGB_HWMON
 	bool "Intel(R) PCI-Express Gigabit adapters HWMON support"
 	default y
diff --git a/drivers/net/ethernet/intel/igb/Makefile b/drivers/net/ethernet/intel/igb/Makefile
index 5bcb2de..1a9b776 100644
--- a/drivers/net/ethernet/intel/igb/Makefile
+++ b/drivers/net/ethernet/intel/igb/Makefile
@@ -33,4 +33,4 @@ obj-$(CONFIG_IGB) += igb.o
 
 igb-objs := igb_main.o igb_ethtool.o e1000_82575.o \
 	    e1000_mac.o e1000_nvm.o e1000_phy.o e1000_mbx.o \
-	    e1000_i210.o igb_ptp.o igb_hwmon.o
+	    e1000_i210.o igb_ptp.o igb_hwmon.o igb_tsn.o
diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
index b9609af..708f705 100644
--- a/drivers/net/ethernet/intel/igb/igb.h
+++ b/drivers/net/ethernet/intel/igb/igb.h
@@ -356,6 +356,7 @@ struct hwmon_buff {
 #define IGB_RETA_SIZE	128
 
 /* board specific private data structure */
+
 struct igb_adapter {
 	unsigned long active_vlans[BITS_TO_LONGS(VLAN_N_VID)];
 
@@ -472,6 +473,13 @@ struct igb_adapter {
 	int copper_tries;
 	struct e1000_info ei;
 	u16 eee_advert;
+
+#if IS_ENABLED(CONFIG_IGB_TSN)
+	/* Reserved BW for class A and B */
+	u16 sra_idleslope_res;
+	u16 srb_idleslope_res;
+	u8 tsn_ready:1;
+#endif	/* IGB_TSN */
 };
 
 #define IGB_FLAG_HAS_MSI		BIT(0)
@@ -552,6 +560,17 @@ void igb_ptp_rx_pktstamp(struct igb_q_vector *q_vector, unsigned char *va,
 			 struct sk_buff *skb);
 int igb_ptp_set_ts_config(struct net_device *netdev, struct ifreq *ifr);
 int igb_ptp_get_ts_config(struct net_device *netdev, struct ifreq *ifr);
+/* This should be the only place where we add ifdeffery
+ * to include tsn-stuff or not. Everything else is located in igb_tsn.c
+ */
+#if IS_ENABLED(CONFIG_IGB_TSN)
+void igb_tsn_init(struct igb_adapter *adapter);
+int igb_tsn_capable(struct net_device *netdev);
+int igb_tsn_link_configure(struct net_device *netdev, enum sr_class sr_class,
+			   u16 framesize, u16 vid);
+#else
+static inline void igb_tsn_init(struct igb_adapter *adapter) { }
+#endif	/* CONFIG_IGB_TSN */
 void igb_set_flag_queue_pairs(struct igb_adapter *, const u32);
 #ifdef CONFIG_IGB_HWMON
 void igb_sysfs_exit(struct igb_adapter *adapter);
diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index ef3d642..4d8789f 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -2142,6 +2142,10 @@ static const struct net_device_ops igb_netdev_ops = {
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	.ndo_poll_controller	= igb_netpoll,
 #endif
+#if IS_ENABLED(CONFIG_IGB_TSN)
+	.ndo_tsn_capable	= igb_tsn_capable,
+	.ndo_tsn_link_configure = igb_tsn_link_configure,
+#endif	/* CONFIG_IGB_TSN */
 	.ndo_fix_features	= igb_fix_features,
 	.ndo_set_features	= igb_set_features,
 	.ndo_fdb_add		= igb_ndo_fdb_add,
@@ -2665,6 +2669,8 @@ static int igb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	/* do hw tstamp init after resetting */
 	igb_ptp_init(adapter);
 
+	igb_tsn_init(adapter);
+
 	dev_info(&pdev->dev, "Intel(R) Gigabit Ethernet Network Connection\n");
 	/* print bus type/speed/width info, not applicable to i354 */
 	if (hw->mac.type != e1000_i354) {
@@ -5323,8 +5329,10 @@ static netdev_tx_t igb_xmit_frame(struct sk_buff *skb,
 	/* The minimum packet size with TCTL.PSP set is 17 so pad the skb
 	 * in order to meet this minimum size requirement.
 	 */
-	if (skb_put_padto(skb, 17))
+	if (skb_put_padto(skb, 17)) {
+		pr_err("%s: skb_put_padto FAILED. skb->len < 17\n", __func__);
 		return NETDEV_TX_OK;
+	}
 
 	return igb_xmit_frame_ring(skb, igb_tx_queue_mapping(adapter, skb));
 }
diff --git a/drivers/net/ethernet/intel/igb/igb_tsn.c b/drivers/net/ethernet/intel/igb/igb_tsn.c
new file mode 100644
index 0000000..641f4f2
--- /dev/null
+++ b/drivers/net/ethernet/intel/igb/igb_tsn.c
@@ -0,0 +1,396 @@
+/*
+ * Copyright(c) 2015-2016 Henrik Austad <haustad@...co.com>
+ *                        Cisco Systems, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+/* FIXME: This should probably be handled by some Makefile-magic */
+
+#if IS_ENABLED(CONFIG_IGB_TSN)
+#include "igb.h"
+#include <linux/module.h>
+
+/* NOTE: keep the defines not present in e1000_regs.h to avoid
+ * cluttering too many files. Once we are pretty stable, these will move
+ * into it's proper home. Until then, make merge a bit easier by
+ * avoiding it
+ */
+
+/* Qav regs */
+#define E1000_IRPBS	 0x02404 /* Rx Packet Buffer Size - RW */
+#define E1000_ITPBS	 0x03404 /* Tx buffer size assignment */
+#define E1000_TQAVCTRL   0x03570 /* Tx Qav Control */
+#define E1000_DTXMXPKTSZ 0x0355C /* DMA TX Maximum Packet Size */
+
+/* Qav defines. */
+#define E1000_TQAVCH_ZERO_CREDIT       0x80000000
+#define E1000_LINK_RATE		       0x7735
+
+/* queue mode, 0=strict, 1=SR mode */
+#define E1000_TQAVCC_QUEUEMODE         0x80000000
+/* Transmit mode, 0=legacy, 1=QAV */
+#define E1000_TQAVCTRL_TXMODE          0x00000001
+/* report DMA time of tx packets */
+#define E1000_TQAVCTRL_1588_STAT_EN    0x00000004
+/* data fetch arbitration */
+#define E1000_TQAVCTRL_DATA_FETCH_ARB  0x00000010
+/* data tx arbitration */
+#define E1000_TQAVCTRL_DATA_TRAN_ARB   0x00000100
+/* data launch time valid */
+#define E1000_TQAVCTRL_DATA_TRAN_TIM   0x00000200
+/* stall SP to guarantee SR */
+#define E1000_TQAVCTRL_SP_WAIT_SR      0x00000400
+
+/* ... and associated shift value */
+#define E1000_TQAVCTRL_FETCH_TM_SHIFT  (16)
+
+/* QAV Tx mode control registers where _n can be 0 or 1. */
+#define E1000_TQAVCC(_idx)			(0x03004 + 0x40 * (_idx))
+
+/* Tx Qav High Credit - See 7.2.7.6 for calculations
+ * intel 8.12.18
+ */
+#define E1000_TQAVHC(_idx)			(0x0300C + 0x40 * (_idx))
+
+/* Queues priority masks where _n and _p can be 0-3. */
+
+#define MAX_FRAME_SIZE 1522
+#define MIN_FRAME_SIZE   64
+
+static int use_tsn = -1;
+static int debug_tsn = -1;
+module_param(use_tsn, int, 0);
+module_param(debug_tsn, int, 0);
+MODULE_PARM_DESC(use_tsn, "use_tsn (0=off, 1=enabled)");
+MODULE_PARM_DESC(debug_tsn, "debug_tsn (0=off, 1=enabled)");
+
+/* For a full list of the registers dumped here, see sec 8.1.3 in the
+ * i210 controller datasheet.
+ */
+static inline void _tsn_dump_regs(struct igb_adapter *adapter)
+{
+	u32 val = 0;
+	struct device *dev;
+	struct e1000_hw *hw = &adapter->hw;
+
+	/* do not dump regs if we're not debugging driver */
+	if (debug_tsn != 1)
+		return;
+
+	dev = &adapter->pdev->dev;
+	dev_info(dev, "num_tx_queues=%d, num_rx_queues=%d\n",
+		 adapter->num_tx_queues, adapter->num_rx_queues);
+
+	/* 0x0008 - E1000_STATUS Device status register */
+	val = rd32(E1000_STATUS);
+	dev_info(&adapter->pdev->dev, "\n");
+	dev_info(dev, "Status: FullDuplex=%s, LinkUp=%s, speed=%0x01x\n",
+		 val & 0x1 ? "FD" : "HD",
+		 val & 0x2 ? "LU" : "LD",
+		 val & 0xc0 >> 6);
+
+	/* E1000_VET vlan ether type */
+	val = rd32(E1000_VET);
+	dev_info(dev, "VLAN ether type: VET.VET=0x%04x, VET.VET_EXT=0x%04x\n",
+		 val & 0xffff, (val >> 16) & 0xffff);
+
+	/* E1000_RXPBS (RXPBSIZE) Rx Packet Buffer Size */
+	val = rd32(E1000_RXPBS);
+	dev_info(dev, "Rx Packet buffer: RXPBSIZE=%dkB, Bmc2ospbsize=%dkB, cfg_ts_en=%s\n",
+		 val & 0x1f,
+		 (val >> 6) & 0x1f,
+		 (val & (1 << 31)) ? "cfg_ts_en" : "cfg_ts_dis");
+
+	/* Transmit stuff */
+	/* E1000_TXPBS (TXPBSIZE) Tx Packet Buffer Size - RW */
+	val = rd32(E1000_TXPBS);
+	dev_info(dev, "Tx Packet buffer: Txpb0size=%dkB, Txpb1size=%dkB, Txpb2size=%dkB, Txpb3size=%dkB, os2Bmcpbsize=%dkB\n",
+		 val & 0x3f, (val >> 6) & 0x3f, (val >> 12) & 0x3f,
+		 (val >> 18) & 0x3f, (val >> 24) & 0x3f);
+
+	/* E1000_TCTL (TCTL) Tx control - RW*/
+	val = rd32(E1000_TCTL);
+	dev_info(dev, "Tx control reg: TxEnable=%s, CT=0x%X\n",
+		 val & 2 ? "EN" : "DIS", (val >> 3) & 0x3F);
+
+	/* TQAVHC     : Transmit Qav High credits 0x300C + 0x40*n - RW */
+	val = rd32(E1000_TQAVHC(0));
+	dev_info(dev, "E1000_TQAVHC0: %0x08x\n", val);
+	val = rd32(E1000_TQAVHC(1));
+	dev_info(dev, "E1000_TQAVHC1: %0x08x\n", val);
+
+	/* TQAVCC[0-1]: Transmit Qav 0x3004 + 0x40*n  - RW */
+	val = rd32(E1000_TQAVCC(0));
+	dev_info(dev, "E1000_TQAVCC0: idleSlope=%02x, QueueMode=%s\n",
+		 val % 0xff,
+		 val > 31 ? "Stream reservation" : "Strict priority");
+	val = rd32(E1000_TQAVCC(1));
+	dev_info(dev, "E1000_TQAVCC1: idleSlope=%02x, QueueMode=%s\n",
+		 val % 0xff,
+		 val > 31 ? "Stream reservation" : "Strict priority");
+
+	/* TQAVCTRL   : Transmit Qav control - RW */
+	val = rd32(E1000_TQAVCTRL);
+	dev_info(dev, "E1000_TQAVCTRL: TransmitMode=%s,1588_STAT_EN=%s,DataFetchARB=%s,DataTranARB=%s,DataTranTIM=%s,SP_WAIT_SR=%s,FetchTimDelta=%dns (0x%04x)\n",
+		 (val & 0x0001) ? "Qav" : "Legacy",
+		 (val & 0x0004) ? "En" : "Dis",
+		 (val & 0x0010) ? "Most Empty" : "Round Robin",
+		 (val & 0x0100) ? "Credit Shaper" : "Strict priority",
+		 (val & 0x0200) ? "Valid" : "N/A",
+		 (val & 0x0400) ? "Wait" : "nowait",
+		 (val >> 16) * 32, (val >> 16));
+}
+
+/* Place the NIC in Qav-mode.
+ *
+ * This will result in a _single_ queue for normal BE traffic, the rest
+ * will be grabbed by the Qav-machinery and kept for strict priority
+ * transmission.
+ *
+ * I210 Datasheet Sec 7.2.7.7 gives a lot of information.
+ */
+void igb_tsn_init(struct igb_adapter *adapter)
+{
+	struct e1000_hw *hw = &adapter->hw;
+	u32 val;
+
+	if (use_tsn != 1) {
+		adapter->tsn_ready = 0;
+		dev_info(&adapter->pdev->dev, "%s got use_tsn > 0 (%d)\n",
+			 __func__, use_tsn);
+		return;
+	}
+
+	if (debug_tsn < 0 || debug_tsn > 1)
+		debug_tsn = 0;
+
+	if (!adapter->pdev) {
+		adapter->tsn_ready = 0;
+		return;
+	}
+
+	switch (adapter->pdev->device) {
+	case 0x1533:   /* E1000_DEV_ID_I210_COPPER */
+	case 0x1536:   /* E1000_DEV_ID_I210_FIBER */
+	case 0x1537:   /* E1000_DEV_ID_I210_SERDES: */
+	case 0x1538:   /* E1000_DEV_ID_I210_SGMII: */
+	case 0x157b:   /* E1000_DEV_ID_I210_COPPER_FLASHLESS: */
+	case 0x157c:   /* E1000_DEV_ID_I210_SERDES_FLASHLESS: */
+		break;
+	default:
+		/* not a known IGB-TSN capable device */
+		adapter->tsn_ready = 0;
+		return;
+	}
+	_tsn_dump_regs(adapter);
+
+	/* Set Tx packet buffer size assignment, see 7.2.7.7 in i210
+	 * PB0: 8kB
+	 * PB1: 8kB
+	 * PB2: 4kB
+	 * PB3: 4kB
+	 * os2bmcsize: 2kB
+	 * sumTx: 26kB
+	 *
+	 * Rxpbsize: 0x20 (32kB)
+	 * bmc2ossize: 0x02
+	 * sumRx: 34kB
+	 *
+	 * See 8.3.1 && 8.3.2
+	 */
+	val = (0x02 << 24 | 0x04 << 18 | 0x04 << 12 | 0x08 << 6 | 0x08);
+	wr32(E1000_ITPBS, val);
+	wr32(E1000_IRPBS, (0x02 << 6 | 0x20));
+
+	/* DMA Tx maximum packet size, the largest frame DMA should transport
+	 * do not allow frames larger than 1522 + preample. Reg expects
+	 * size in 64B increments. 802.1BA 6.3
+	 * Round up to 1536 to handle 64B increments
+	 *
+	 * Initial value: 0x98 (152 => 9728 bytes)
+	 */
+	wr32(E1000_DTXMXPKTSZ, 1536 >> 6);
+
+	/* Place card in Qav-mode, use tx-queue 0,1 for Qav
+	 * (Credit-based shaper), 2,3 for standard priority (and
+	 * best-effort) traffic.
+	 *
+	 * i210 8.12.19 and 8.12.21
+	 *
+	 * - Fetch: most empty and time based (not round-robin)
+	 * - Transmit: Credit based shaper for SR queues
+	 * - Data launch time valid (in Qav mode)
+	 * - Wait for SR queues to ensure that launch time is always valid.
+	 * - Set ~10us wait-time-delta, 32ns granularity
+	 *
+	 * Do *not* enable Tx for shaper (E1000_TQAVCTRL_DATA_TRAN_ARB)
+	 * yet as we do not have data to Tx
+	 */
+	val = E1000_TQAVCTRL_TXMODE           |
+		E1000_TQAVCTRL_DATA_FETCH_ARB |
+		E1000_TQAVCTRL_DATA_TRAN_TIM  |
+		E1000_TQAVCTRL_SP_WAIT_SR     |
+		320 << E1000_TQAVCTRL_FETCH_TM_SHIFT;
+
+	wr32(E1000_TQAVCTRL, val);
+
+	/* For now, only set CreditBased shaper for A and B, not set
+	 * idleSlope as we have not yet gotten any streams.
+	 * 8.12.19
+	 */
+	wr32(E1000_TQAVCC(0), E1000_TQAVCC_QUEUEMODE);
+	wr32(E1000_TQAVCC(1), E1000_TQAVCC_QUEUEMODE);
+
+	wr32(E1000_TQAVHC(0), E1000_TQAVCH_ZERO_CREDIT);
+	wr32(E1000_TQAVHC(1), E1000_TQAVCH_ZERO_CREDIT);
+
+	/* reset Tx Descriptor tail and head for the queues */
+	wr32(E1000_TDT(0), 0);
+	wr32(E1000_TDT(1), 0);
+	wr32(E1000_TDH(0), 0);
+	wr32(E1000_TDH(1), 0);
+
+	_tsn_dump_regs(adapter);
+	dev_info(&adapter->pdev->dev, "\n");
+
+	adapter->sra_idleslope_res = 0;
+	adapter->srb_idleslope_res = 0;
+	adapter->tsn_ready = 1;
+
+	dev_info(&adapter->pdev->dev, "%s: setup done\n", __func__);
+}
+
+int igb_tsn_capable(struct net_device *netdev)
+{
+	struct igb_adapter *adapter;
+
+	if (!netdev)
+		return -EINVAL;
+	adapter = netdev_priv(netdev);
+	if (use_tsn == 1)
+		return adapter->tsn_ready == 1;
+	return 0;
+}
+
+/* igb_tsn_link_configure - configure NIC to handle a new stream
+ *
+ * @netdev: pointer to NIC device
+ * @class: the class for the stream used to find the correct queue.
+ * @framesize: size of each frame, *including* headers (not preamble)
+ * @vid: VLAN ID
+ *
+ * NOTE: the sr_class only instructs the driver which queue to use, not
+ * what priority the network expects for a given class. This is
+ * something userspace must find out and then let the tsn-driver set in
+ * the frame before xmit.
+ *
+ * FIXME: remove bw-req from a stream that goes away.
+ */
+int igb_tsn_link_configure(struct net_device *netdev, enum sr_class class,
+			   u16 framesize, u16 vid)
+{
+	/* FIXME: push into adapter-storage */
+	static int class_a_size;
+	static int class_b_size;
+	int err;
+	u32 idle_slope_a = 0;
+	u32 idle_slope_b = 0;
+	u32 new_is = 0;
+	u32 hicred_a = 0;
+	u32 hicred_b = 0;
+	u32 tqavctrl;
+
+	struct igb_adapter *adapter;
+	struct e1000_hw *hw;
+
+	if (!netdev)
+		return -EINVAL;
+	adapter  = netdev_priv(netdev);
+	hw = &adapter->hw;
+
+	if (!igb_tsn_capable(netdev)) {
+		pr_err("%s:  NIC not capable\n", __func__);
+		return -EINVAL;
+	}
+
+	if (framesize > MAX_FRAME_SIZE || framesize < MIN_FRAME_SIZE) {
+		pr_err("%s: framesize (%u) must be [%d,%d]\n", __func__,
+		       framesize, MIN_FRAME_SIZE, MAX_FRAME_SIZE);
+		return -EINVAL;
+	}
+
+	/* TODO: is this the correct place/way? Is it required? */
+	rtnl_lock();
+	pr_info("%s: adding VLAN %u to HW filter on device %s\n",
+		__func__, vid, netdev->name);
+	err = vlan_vid_add(netdev, htons(ETH_P_8021Q), vid);
+	if (err != 0)
+		pr_err("%s: error adding vlan %u, res=%d\n",
+		       __func__, vid, err);
+	rtnl_unlock();
+
+	/* Grab current values of idle_slope */
+	idle_slope_a = rd32(E1000_TQAVHC(0)) & ~E1000_TQAVCH_ZERO_CREDIT;
+	idle_slope_b = rd32(E1000_TQAVHC(1)) & ~E1000_TQAVCH_ZERO_CREDIT;
+
+	/* Calculate new idle slope and add to appropriate idle_slope
+	 * idle_slope = BW * linkrate * 2 (0r 0.2 for 100Mbit)
+	 * BW: % of total bandwidth
+	 */
+	new_is = framesize * E1000_LINK_RATE * 16 / 1000000;
+
+	switch (class) {
+	case SR_CLASS_A:
+		new_is *= 2; /* A is 8kHz, B is 4kHz */
+		idle_slope_a += new_is;
+		class_a_size  = framesize;
+		break;
+	case SR_CLASS_B:
+		idle_slope_b += new_is;
+		class_b_size  = framesize;
+		break;
+	default:
+		pr_err("%s: unhandled SR-class (%d)\n", __func__, class);
+		return -EINVAL;
+	}
+
+	/* HiCred: cred obtained while waiting for current frame &&
+	 * higher-class frames to finish xmit.
+	 *
+	 * Covered in detail in 7.2.7.6 in i210 datasheet
+	 * For class A: only worst-case framesize that just started;
+	 *		i.e. 1522 * idleSlope / linkrate;
+	 * For class B: (worst-case framesize + burstSize(A))*idleSlope
+	 *
+	 * See 802.1Q Annex L, eq L.10 for hicred_a and L.41 for
+	 * hicred_b
+	 */
+	if (class == SR_CLASS_A) {
+		hicred_a = E1000_TQAVCH_ZERO_CREDIT + idle_slope_a * MAX_FRAME_SIZE / E1000_LINK_RATE;
+		wr32(E1000_TQAVCC(0), E1000_TQAVCC_QUEUEMODE | idle_slope_a);
+		wr32(E1000_TQAVHC(0), hicred_a);
+	} else {
+		hicred_b = E1000_TQAVCH_ZERO_CREDIT | idle_slope_b * (MAX_FRAME_SIZE + class_a_size) / (E1000_LINK_RATE - idle_slope_a);
+		wr32(E1000_TQAVCC(1), E1000_TQAVCC_QUEUEMODE | idle_slope_b);
+		wr32(E1000_TQAVHC(1), hicred_b);
+	}
+
+	/* Enable Tx for shaper now that we have data */
+	tqavctrl = rd32(E1000_TQAVCTRL);
+	if (!(tqavctrl & E1000_TQAVCTRL_DATA_TRAN_ARB)) {
+		tqavctrl |= E1000_TQAVCTRL_DATA_TRAN_ARB;
+		wr32(E1000_TQAVCTRL, tqavctrl);
+	}
+	_tsn_dump_regs(netdev_priv(netdev));
+	return 0;
+}
+
+#endif	/* #if IS_ENABLED(CONFIG_IGB_TSN) */
-- 
2.7.4

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