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Commit 03191656 authored by Frank Li's avatar Frank Li Committed by David S. Miller
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net: fec: workaround stop tx during errata ERR006358 



If the ready bit in the transmit buffer descriptor (TxBD[R])
is previously detected as not set during a prior frame transmission,
then the ENET_TDAR[TDAR] bit is cleared at a later time, even if
additional TxBDs were added to the ring and the ENET_TDAR[TDAR]
bit is set. This results in frames not being transmitted until
there is a 0-to-1 transition on ENET_TDAR[TDAR].

Workarounds:
code can use the transmit frame interrupt flag (ENET_EIR[TXF])
as a method to detect whether the ENET has completed transmission
and the ENET_TDAR[TDAR] has been cleared. If ENET_TDAR[TDAR] is
detected as cleared when packets are queued and waiting for transmit,
then a write to the TDAR bit will restart TxBD processing.

This case main happen when loading is light. A ethernet package may
not send out utile next package put into tx queue.

How to test:
while [ true ]
do
	ping <IP> -s 10000 -w 4
	ping <IP> -s 6000 -w 2
	ping <IP> -s 4000 -w 2
	ping <IP> -s 10000 -w 2
done

You will see below result in overnight test.

6008 bytes from 10.192.242.116: seq=1 ttl=128 time=0.722 ms
4008 bytes from 10.192.242.116: seq=0 ttl=128 time=1001.008 ms
4008 bytes from 10.192.242.116: seq=1 ttl=128 time=1.010 ms
10008 bytes from 10.192.242.116: seq=0 ttl=128 time=0.896 ms

After apply this patch, >1000ms delay disappear.

Signed-off-by: default avatarFrank Li <Frank.Li@freescale.com>
Acked-by: default avatarFugang Duan <B38611@freescale.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c2534384

drivers/net/ethernet/freescale/fec.h

+1 −0
Original line number Diff line number Diff line
@@ -259,6 +259,7 @@ struct bufdesc_ex { 
struct fec_enet_delayed_work {

	struct delayed_work delay_work;

	bool timeout;

	bool trig_tx;

};



/* The FEC buffer descriptors track the ring buffers.  The rx_bd_base and

drivers/net/ethernet/freescale/fec_main.c

+30 −2
Original line number Diff line number Diff line
@@ -93,6 +93,20 @@ static void set_multicast_list(struct net_device *ndev); 
#define FEC_QUIRK_HAS_CSUM		(1 << 5)

/* Controller has hardware vlan support */

#define FEC_QUIRK_HAS_VLAN		(1 << 6)

/* ENET IP errata ERR006358

 *

 * If the ready bit in the transmit buffer descriptor (TxBD[R]) is previously

 * detected as not set during a prior frame transmission, then the

 * ENET_TDAR[TDAR] bit is cleared at a later time, even if additional TxBDs

 * were added to the ring and the ENET_TDAR[TDAR] bit is set. This results in

 * If the ready bit in the transmit buffer descriptor (TxBD[R]) is previously

 * detected as not set during a prior frame transmission, then the

 * ENET_TDAR[TDAR] bit is cleared at a later time, even if additional TxBDs

 * were added to the ring and the ENET_TDAR[TDAR] bit is set. This results in

 * frames not being transmitted until there is a 0-to-1 transition on

 * ENET_TDAR[TDAR].

 */

#define FEC_QUIRK_ERR006358            (1 << 7)



static struct platform_device_id fec_devtype[] = {

	{
@@ -112,7 +126,7 @@ static struct platform_device_id fec_devtype[] = { 
		.name = "imx6q-fec",

		.driver_data = FEC_QUIRK_ENET_MAC | FEC_QUIRK_HAS_GBIT |

				FEC_QUIRK_HAS_BUFDESC_EX | FEC_QUIRK_HAS_CSUM |

				FEC_QUIRK_HAS_VLAN,

				FEC_QUIRK_HAS_VLAN | FEC_QUIRK_ERR006358,

	}, {

		.name = "mvf600-fec",

		.driver_data = FEC_QUIRK_ENET_MAC,
@@ -275,7 +289,7 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev) 
	struct fec_enet_private *fep = netdev_priv(ndev);

	const struct platform_device_id *id_entry =

				platform_get_device_id(fep->pdev);

	struct bufdesc *bdp;

	struct bufdesc *bdp, *bdp_pre;

	void *bufaddr;

	unsigned short	status;

	unsigned int index;
@@ -370,6 +384,15 @@ fec_enet_start_xmit(struct sk_buff *skb, struct net_device *ndev) 
				ebdp->cbd_esc |= BD_ENET_TX_PINS;

		}

	}



	bdp_pre = fec_enet_get_prevdesc(bdp, fep->bufdesc_ex);

	if ((id_entry->driver_data & FEC_QUIRK_ERR006358) &&

	    !(bdp_pre->cbd_sc & BD_ENET_TX_READY)) {

		fep->delay_work.trig_tx = true;

		schedule_delayed_work(&(fep->delay_work.delay_work),

					msecs_to_jiffies(1));

	}



	/* If this was the last BD in the ring, start at the beginning again. */

	if (status & BD_ENET_TX_WRAP)

		bdp = fep->tx_bd_base;
@@ -689,6 +712,11 @@ static void fec_enet_work(struct work_struct *work) 
		fec_restart(fep->netdev, fep->full_duplex);

		netif_wake_queue(fep->netdev);

	}



	if (fep->delay_work.trig_tx) {

		fep->delay_work.trig_tx = false;

		writel(0, fep->hwp + FEC_X_DES_ACTIVE);

	}

}



static void