net: lan966x: Stop using packing library

When a frame is injected from CPU, it is required to create an IFH(Inter
frame header) which sits in front of the frame that is transmitted.
This IFH, contains different fields like destination port, to bypass the
analyzer, priotity, etc. Lan966x it is using packing library to set and
get the fields of this IFH. But this seems to be an expensive
operations.
If this is changed with a simpler implementation, the RX will be
improved with ~5Mbit while on the TX is a much bigger improvement as it
is required to set more fields. Below are the numbers for TX.

Before:
[  5]   0.00-10.02  sec   439 MBytes   367 Mbits/sec    0 sender

After:
[  5]   0.00-10.00  sec   578 MBytes   485 Mbits/sec    0 sender
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/lan966x/Kconfig

@@ -6,7 +6,6 @@ config LAN966X_SWITCH
 	depends on NET_SWITCHDEV
 	depends on BRIDGE || BRIDGE=n
 	select PHYLINK
-	select PACKING
 	select PAGE_POOL
 	select VCAP
 	help

drivers/net/ethernet/microchip/lan966x/lan966x_main.c

@@ -7,7 +7,6 @@
 #include <linux/ip.h>
 #include <linux/of_platform.h>
 #include <linux/of_net.h>
-#include <linux/packing.h>
 #include <linux/phy/phy.h>
 #include <linux/reset.h>
 #include <net/addrconf.h>
@@ -305,46 +304,57 @@ static int lan966x_port_ifh_xmit(struct sk_buff *skb,
 	return NETDEV_TX_BUSY;
 }
 
+static void lan966x_ifh_set(u8 *ifh, size_t val, size_t pos, size_t length)
+{
+	int i = 0;
+
+	do {
+		u8 p = IFH_LEN_BYTES - (pos + i) / 8 - 1;
+		u8 v = val >> i & 0xff;
+
+		/* There is no need to check for limits of the array, as these
+		 * will never be written
+		 */
+		ifh[p] |= v << ((pos + i) % 8);
+		ifh[p - 1] |= v >> (8 - (pos + i) % 8);
+
+		i += 8;
+	} while (i < length);
+}
+
 void lan966x_ifh_set_bypass(void *ifh, u64 bypass)
 {
-	packing(ifh, &bypass, IFH_POS_BYPASS + IFH_WID_BYPASS - 1,
-		IFH_POS_BYPASS, IFH_LEN * 4, PACK, 0);
+	lan966x_ifh_set(ifh, bypass, IFH_POS_BYPASS, IFH_WID_BYPASS);
 }
 
-void lan966x_ifh_set_port(void *ifh, u64 bypass)
+void lan966x_ifh_set_port(void *ifh, u64 port)
 {
-	packing(ifh, &bypass, IFH_POS_DSTS + IFH_WID_DSTS - 1,
-		IFH_POS_DSTS, IFH_LEN * 4, PACK, 0);
+	lan966x_ifh_set(ifh, port, IFH_POS_DSTS, IFH_WID_DSTS);
 }
 
-static void lan966x_ifh_set_qos_class(void *ifh, u64 bypass)
+static void lan966x_ifh_set_qos_class(void *ifh, u64 qos)
 {
-	packing(ifh, &bypass, IFH_POS_QOS_CLASS + IFH_WID_QOS_CLASS - 1,
-		IFH_POS_QOS_CLASS, IFH_LEN * 4, PACK, 0);
+	lan966x_ifh_set(ifh, qos, IFH_POS_QOS_CLASS, IFH_WID_QOS_CLASS);
 }
 
-static void lan966x_ifh_set_ipv(void *ifh, u64 bypass)
+static void lan966x_ifh_set_ipv(void *ifh, u64 ipv)
 {
-	packing(ifh, &bypass, IFH_POS_IPV + IFH_WID_IPV - 1,
-		IFH_POS_IPV, IFH_LEN * 4, PACK, 0);
+	lan966x_ifh_set(ifh, ipv, IFH_POS_IPV, IFH_WID_IPV);
 }
 
 static void lan966x_ifh_set_vid(void *ifh, u64 vid)
 {
-	packing(ifh, &vid, IFH_POS_TCI + IFH_WID_TCI - 1,
-		IFH_POS_TCI, IFH_LEN * 4, PACK, 0);
+	lan966x_ifh_set(ifh, vid, IFH_POS_TCI, IFH_WID_TCI);
 }
 
 static void lan966x_ifh_set_rew_op(void *ifh, u64 rew_op)
 {
-	packing(ifh, &rew_op, IFH_POS_REW_CMD + IFH_WID_REW_CMD - 1,
-		IFH_POS_REW_CMD, IFH_LEN * 4, PACK, 0);
+	lan966x_ifh_set(ifh, rew_op, IFH_POS_REW_CMD, IFH_WID_REW_CMD);
 }
 
 static void lan966x_ifh_set_timestamp(void *ifh, u64 timestamp)
 {
-	packing(ifh, &timestamp, IFH_POS_TIMESTAMP + IFH_WID_TIMESTAMP - 1,
-		IFH_POS_TIMESTAMP, IFH_LEN * 4, PACK, 0);
+	lan966x_ifh_set(ifh, timestamp, IFH_POS_TIMESTAMP, IFH_WID_TIMESTAMP);
 }
 
 static netdev_tx_t lan966x_port_xmit(struct sk_buff *skb,
@@ -582,22 +592,38 @@ static int lan966x_rx_frame_word(struct lan966x *lan966x, u8 grp, u32 *rval)
 	}
 }
 
+static u64 lan966x_ifh_get(u8 *ifh, size_t pos, size_t length)
+{
+	u64 val = 0;
+	u8 v;
+
+	for (int i = 0; i < length ; i++) {
+		int j = pos + i;
+		int k = j % 8;
+
+		if (i == 0 || k == 0)
+			v = ifh[IFH_LEN_BYTES - (j / 8) - 1];
+
+		if (v & (1 << k))
+			val |= (1 << i);
+	}
+
+	return val;
+}
+
 void lan966x_ifh_get_src_port(void *ifh, u64 *src_port)
 {
-	packing(ifh, src_port, IFH_POS_SRCPORT + IFH_WID_SRCPORT - 1,
-		IFH_POS_SRCPORT, IFH_LEN * 4, UNPACK, 0);
+	*src_port = lan966x_ifh_get(ifh, IFH_POS_SRCPORT, IFH_WID_SRCPORT);
 }
 
 static void lan966x_ifh_get_len(void *ifh, u64 *len)
 {
-	packing(ifh, len, IFH_POS_LEN + IFH_WID_LEN - 1,
-		IFH_POS_LEN, IFH_LEN * 4, UNPACK, 0);
+	*len = lan966x_ifh_get(ifh, IFH_POS_LEN, IFH_WID_LEN);
 }
 
 void lan966x_ifh_get_timestamp(void *ifh, u64 *timestamp)
 {
-	packing(ifh, timestamp, IFH_POS_TIMESTAMP + IFH_WID_TIMESTAMP - 1,
-		IFH_POS_TIMESTAMP, IFH_LEN * 4, UNPACK, 0);
+	*timestamp = lan966x_ifh_get(ifh, IFH_POS_TIMESTAMP, IFH_WID_TIMESTAMP);
 }
 
 static irqreturn_t lan966x_xtr_irq_handler(int irq, void *args)