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net: fec: workaround stop tx during errata ERR006358

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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: Frank Li <Frank.Li@freescale.com>
Acked-by: Fugang Duan  <B38611@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Frank Li 2013-07-25 14:05:53 +08:00 committed by David S. Miller
parent c253438423
commit 031916568a
2 changed files with 31 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/net/ethernet/freescale/fec.h
View File

@ -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

32
drivers/net/ethernet/freescale/fec_main.c
View File

@ -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