net: stmmac: Avoid DMA_CHAN_CONTROL write if no Split Header support

BugLink: https://bugs.launchpad.net/bugs/1953731
commit f8e7dfd6fdabb831846ab1970a875746559d491b upstream.

The driver assumes that split headers can be enabled/disabled without
stopping/starting the device, so it writes DMA_CHAN_CONTROL from
stmmac_set_features().  However, on my system (IP v5.10a without Split
Header support), simply writing DMA_CHAN_CONTROL when DMA is running
(for example, with the commands below) leads to a TX watchdog timeout.

 host$ socat TCP-LISTEN:1024,fork,reuseaddr - &
 device$ ethtool -K eth0 tso off
 device$ ethtool -K eth0 tso on
 device$ dd if=/dev/zero bs=1M count=10 | socat - TCP4:host:1024
 <tx watchdog timeout>

Note that since my IP is configured without Split Header support, the
driver always just reads and writes the same value to the
DMA_CHAN_CONTROL register.

I don't have access to any platforms with Split Header support so I
don't know if these writes to the DMA_CHAN_CONTROL while DMA is running
actually work properly on such systems.  I could not find anything in
the databook that says that DMA_CHAN_CONTROL should not be written when
the DMA is running.

But on systems without Split Header support, there is in any case no
need to call enable_sph() in stmmac_set_features() at all since SPH can
never be toggled, so we can avoid the watchdog timeout there by skipping
this call.

Fixes: 8c6fc097a2f4acf ("net: stmmac: gmac4+: Add Split Header support")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 1cf94248c2217037f8235eaec6675019d60d2464..3422f0746d82532a1c5dae05c3311542909a7fbe 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5531,8 +5531,6 @@ static int stmmac_set_features(struct net_device *netdev,
                               netdev_features_t features)
 {
        struct stmmac_priv *priv = netdev_priv(netdev);
-       bool sph_en;
-       u32 chan;
 
        /* Keep the COE Type in case of csum is supporting */
        if (features & NETIF_F_RXCSUM)
@@ -5544,10 +5542,13 @@ static int stmmac_set_features(struct net_device *netdev,
         */
        stmmac_rx_ipc(priv, priv->hw);
 
-       sph_en = (priv->hw->rx_csum > 0) && priv->sph;
+       if (priv->sph_cap) {
+               bool sph_en = (priv->hw->rx_csum > 0) && priv->sph;
+               u32 chan;
 
-       for (chan = 0; chan < priv->plat->rx_queues_to_use; chan++)
-               stmmac_enable_sph(priv, priv->ioaddr, sph_en, chan);
+               for (chan = 0; chan < priv->plat->rx_queues_to_use; chan++)
+                       stmmac_enable_sph(priv, priv->ioaddr, sph_en, chan);
+       }
 
        return 0;
 }