Date:   Thu,  9 Feb 2023 17:24:22 +0800
From:   wei.fang@....com
To:     shenwei.wang@....com, xiaoning.wang@....com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org
Cc:     linux-imx@....com, linux-kernel@...r.kernel.org
Subject: [PATCH net-next] net: fec: add CBS offload support

From: Wei Fang <wei.fang@....com>

The FEC hardware supports the Credit-based shaper (CBS) which control
the bandwidth distribution between normal traffic and time-sensitive
traffic with respect to the total link bandwidth available.
But notice that the bandwidth allocation of hardware is restricted to
certain values. Below is the equation which is used to calculate the
BW (bandwidth) fraction for per class:
	BW fraction = 1 / (1 + 512 / idle_slope)

For values of idle_slope less than 128, idle_slope = 2 ^ n, when n =
0,1,2,...,6. For values equal to or greater than 128, idle_slope =
128 * m, where m = 1,2,3,...,12.
Example 1. idle_slope = 64, therefore BW fraction = 0.111.
Example 2. idle_slope = 128, therefore BW fraction = 0.200.

Here is an example command to set 200Mbps bandwidth on 1000Mbps port
for TC 2 and 111Mbps for TC 3.
tc qdisc add dev eth0 parent root handle 100 mqprio num_tc 3 map \
0 0 2 1 0 0 0 0 0 0 0 0 0 0 0 0 queues 1@0 1@1 1@2 hw 0
tc qdisc replace dev eth0 parent 100:2 cbs idleslope 200000 \
sendslope -800000 hicredit 153 locredit -1389 offload 1
tc qdisc replace dev eth0 parent 100:3 cbs idleslope 111000 \
sendslope -889000 hicredit 90 locredit -892 offload 1

Signed-off-by: Wei Fang <wei.fang@....com>
---
 drivers/net/ethernet/freescale/fec.h      |   4 +
 drivers/net/ethernet/freescale/fec_main.c | 106 ++++++++++++++++++++++
 2 files changed, 110 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
index 5ba1e0d71c68..ad5f968aa086 100644
--- a/drivers/net/ethernet/freescale/fec.h
+++ b/drivers/net/ethernet/freescale/fec.h
@@ -340,6 +340,10 @@ struct bufdesc_ex {
 #define RCMR_CMP(X)		(((X) == 1) ? RCMR_CMP_1 : RCMR_CMP_2)
 #define FEC_TX_BD_FTYPE(X)	(((X) & 0xf) << 20)
 
+#define FEC_QOS_TX_SHEME_MASK	GENMASK(2, 0)
+#define CREDIT_BASED_SCHEME	0
+#define ROUND_ROBIN_SCHEME	1
+
 /* The number of Tx and Rx buffers.  These are allocated from the page
  * pool.  The code may assume these are power of two, so it it best
  * to keep them that size.
diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index c73e25f8995e..3bb3a071fa0c 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -66,6 +66,7 @@
 #include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
 #include <soc/imx/cpuidle.h>
+#include <net/pkt_sched.h>
 #include <linux/filter.h>
 #include <linux/bpf.h>
 
@@ -3232,6 +3233,110 @@ static int fec_enet_ioctl(struct net_device *ndev, struct ifreq *rq, int cmd)
 	return phy_mii_ioctl(phydev, rq, cmd);
 }
 
+static u32 fec_enet_get_idle_slope(u8 bw)
+{
+	u32 idle_slope, quotient, msb;
+
+	/* Convert bw to hardware idle slope */
+	idle_slope = (512 * bw) / (100 - bw);
+
+	if (idle_slope >= 128) {
+		/* For values equal to or greater than 128, idle_slope = 128 * m,
+		 * where m = 1, 2, 3, ...12. Here we use the rounding method.
+		 */
+		quotient = idle_slope / 128;
+		if (idle_slope >= quotient * 128 + 64)
+			idle_slope = 128 * (quotient + 1);
+		else
+			idle_slope = 128 * quotient;
+
+		goto end;
+	}
+
+	/* For values less than 128, idle_slope = 2 ^ n, where
+	 * n = 0, 1, 2, ...6. Here we use the rounding method.
+	 * So the minimum of idle_slope is 1.
+	 */
+	msb = fls(idle_slope);
+
+	if (msb == 0 || msb == 1) {
+		idle_slope = 1;
+		goto end;
+	}
+
+	msb -= 1;
+	if (idle_slope >= (1 << msb) + (1 << (msb - 1)))
+		idle_slope = 1 << (msb + 1);
+	else
+		idle_slope = 1 << msb;
+
+end:
+	return idle_slope;
+}
+
+static int fec_enet_setup_tc_cbs(struct net_device *ndev, void *type_data)
+{
+	struct fec_enet_private *fep = netdev_priv(ndev);
+	struct tc_cbs_qopt_offload *cbs = type_data;
+	int queue =  cbs->queue;
+	u32 speed = fep->speed;
+	u32 val, idle_slope;
+	u8 bw;
+
+	if (!(fep->quirks & FEC_QUIRK_HAS_AVB))
+		return -EOPNOTSUPP;
+
+	/* Queue 1 for Class A, Queue 2 for Class B, so the ENET must has
+	 * three queues.
+	 */
+	if (fep->num_tx_queues != FEC_ENET_MAX_TX_QS)
+		return -EOPNOTSUPP;
+
+	/* Queue 0 is not AVB capable */
+	if (queue <= 0 || queue >= fep->num_tx_queues)
+		return -EINVAL;
+
+	val = readl(fep->hwp + FEC_QOS_SCHEME);
+	val &= ~FEC_QOS_TX_SHEME_MASK;
+	if (!cbs->enable) {
+		val |= ROUND_ROBIN_SCHEME;
+		writel(val, fep->hwp + FEC_QOS_SCHEME);
+
+		return 0;
+	}
+
+	val |= CREDIT_BASED_SCHEME;
+	writel(val, fep->hwp + FEC_QOS_SCHEME);
+
+	/* cbs->idleslope is in kilobits per second. speed is the port rate
+	 * in megabits per second. So bandwidth ratio bw = (idleslope /
+	 * (speed * 1000)) * 100, the unit is percentage.
+	 */
+	bw = cbs->idleslope / (speed * 10UL);
+	/* bw% can not >= 100% */
+	if (bw >= 100)
+		return -EINVAL;
+	idle_slope = fec_enet_get_idle_slope(bw);
+
+	val = readl(fep->hwp + FEC_DMA_CFG(queue));
+	val &= ~IDLE_SLOPE_MASK;
+	val |= idle_slope & IDLE_SLOPE_MASK;
+	writel(val, fep->hwp + FEC_DMA_CFG(queue));
+
+	return 0;
+}
+
+static int fec_enet_setup_tc(struct net_device *ndev, enum tc_setup_type type,
+			     void *type_data)
+{
+	switch (type) {
+	case TC_SETUP_QDISC_CBS:
+		return fec_enet_setup_tc_cbs(ndev, type_data);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
 static void fec_enet_free_buffers(struct net_device *ndev)
 {
 	struct fec_enet_private *fep = netdev_priv(ndev);
@@ -3882,6 +3987,7 @@ static const struct net_device_ops fec_netdev_ops = {
 	.ndo_tx_timeout		= fec_timeout,
 	.ndo_set_mac_address	= fec_set_mac_address,
 	.ndo_eth_ioctl		= fec_enet_ioctl,
+	.ndo_setup_tc	= fec_enet_setup_tc,
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	.ndo_poll_controller	= fec_poll_controller,
 #endif
-- 
2.25.1

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