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authorBen Hutchings <ben.hutchings@codethink.co.uk>2015-01-27 00:49:32 +0000
committerDavid S. Miller <davem@davemloft.net>2015-01-27 00:18:53 -0800
commit740c7f31c094703cfb3902412e66e243eb24b707 (patch)
tree82a90d281a4fe3c0e9dac8a79b05a9906834ecb0 /drivers/net
parentdc1d0e6d55006a48ebc0f40a74485ca430f05046 (diff)
downloadlinux-740c7f31c094703cfb3902412e66e243eb24b707.tar.bz2
sh_eth: Ensure DMA engines are stopped before freeing buffers
Currently we try to clear EDRRR and EDTRR and immediately continue to free buffers. This is unsafe because: - In general, register writes are not serialised with DMA, so we still have to wait for DMA to complete somehow - The R8A7790 (R-Car H2) manual states that the TX running flag cannot be cleared by writing to EDTRR - The same manual states that clearing the RX running flag only stops RX DMA at the next packet boundary I applied this patch to the driver to detect DMA writes to freed buffers: > --- a/drivers/net/ethernet/renesas/sh_eth.c > +++ b/drivers/net/ethernet/renesas/sh_eth.c > @@ -1098,7 +1098,14 @@ static void sh_eth_ring_free(struct net_device *ndev) > /* Free Rx skb ringbuffer */ > if (mdp->rx_skbuff) { > for (i = 0; i < mdp->num_rx_ring; i++) > + memcpy(mdp->rx_skbuff[i]->data, > + "Hello, world", 12); > + msleep(100); > + for (i = 0; i < mdp->num_rx_ring; i++) { > + WARN_ON(memcmp(mdp->rx_skbuff[i]->data, > + "Hello, world", 12)); > dev_kfree_skb(mdp->rx_skbuff[i]); > + } > } > kfree(mdp->rx_skbuff); > mdp->rx_skbuff = NULL; then ran the loop: while ethtool -G eth0 rx 128 ; ethtool -G eth0 rx 64; do echo -n .; done and 'ping -f' toward the sh_eth port from another machine. The warning fired several times a minute. To fix these issues: - Deactivate all TX descriptors rather than writing to EDTRR - As there seems to be no way of telling when RX DMA is stopped, perform a soft reset to ensure that both DMA enginess are stopped - To reduce the possibility of the reset truncating a transmitted frame, disable egress and wait a reasonable time to reach a packet boundary before resetting - Update statistics before resetting (The 'reasonable time' does not allow for CS/CD in half-duplex mode, but half-duplex no longer seems reasonable!) Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net')
-rw-r--r--drivers/net/ethernet/renesas/sh_eth.c39
1 files changed, 32 insertions, 7 deletions
diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
index bb15cd83134f..245166bbccfd 100644
--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/drivers/net/ethernet/renesas/sh_eth.c
@@ -396,6 +396,9 @@ static const u16 sh_eth_offset_fast_sh3_sh2[SH_ETH_MAX_REGISTER_OFFSET] = {
[TSU_ADRL31] = 0x01fc,
};
+static void sh_eth_rcv_snd_disable(struct net_device *ndev);
+static struct net_device_stats *sh_eth_get_stats(struct net_device *ndev);
+
static bool sh_eth_is_gether(struct sh_eth_private *mdp)
{
return mdp->reg_offset == sh_eth_offset_gigabit;
@@ -1358,6 +1361,33 @@ static int sh_eth_dev_init(struct net_device *ndev, bool start)
return ret;
}
+static void sh_eth_dev_exit(struct net_device *ndev)
+{
+ struct sh_eth_private *mdp = netdev_priv(ndev);
+ int i;
+
+ /* Deactivate all TX descriptors, so DMA should stop at next
+ * packet boundary if it's currently running
+ */
+ for (i = 0; i < mdp->num_tx_ring; i++)
+ mdp->tx_ring[i].status &= ~cpu_to_edmac(mdp, TD_TACT);
+
+ /* Disable TX FIFO egress to MAC */
+ sh_eth_rcv_snd_disable(ndev);
+
+ /* Stop RX DMA at next packet boundary */
+ sh_eth_write(ndev, 0, EDRRR);
+
+ /* Aside from TX DMA, we can't tell when the hardware is
+ * really stopped, so we need to reset to make sure.
+ * Before doing that, wait for long enough to *probably*
+ * finish transmitting the last packet and poll stats.
+ */
+ msleep(2); /* max frame time at 10 Mbps < 1250 us */
+ sh_eth_get_stats(ndev);
+ sh_eth_reset(ndev);
+}
+
/* free Tx skb function */
static int sh_eth_txfree(struct net_device *ndev)
{
@@ -1986,9 +2016,7 @@ static int sh_eth_set_ringparam(struct net_device *ndev,
napi_synchronize(&mdp->napi);
sh_eth_write(ndev, 0x0000, EESIPR);
- /* Stop the chip's Tx and Rx processes. */
- sh_eth_write(ndev, 0, EDTRR);
- sh_eth_write(ndev, 0, EDRRR);
+ sh_eth_dev_exit(ndev);
/* Free all the skbuffs in the Rx queue. */
sh_eth_ring_free(ndev);
@@ -2207,11 +2235,8 @@ static int sh_eth_close(struct net_device *ndev)
napi_disable(&mdp->napi);
sh_eth_write(ndev, 0x0000, EESIPR);
- /* Stop the chip's Tx and Rx processes. */
- sh_eth_write(ndev, 0, EDTRR);
- sh_eth_write(ndev, 0, EDRRR);
+ sh_eth_dev_exit(ndev);
- sh_eth_get_stats(ndev);
/* PHY Disconnect */
if (mdp->phydev) {
phy_stop(mdp->phydev);