From: Remi Pommarel <repk@triplefau.lt>
Date: Sun, 8 Mar 2020 10:25:56 +0100
Subject: net: stmmac: dwmac1000: Disable ACS if enhanced descs are not used
Git-commit: b723bd933980f4956dabc8a8d84b3e83be8d094c
Patch-mainline: 5.6-rc6
References: networking-stable-20_03_14

ACS (auto PAD/FCS stripping) removes FCS off 802.3 packets (LLC) so that
there is no need to manually strip it for such packets. The enhanced DMA
descriptors allow to flag LLC packets so that the receiving callback can
use that to strip FCS manually or not. On the other hand, normal
descriptors do not support that.

Thus in order to not truncate LLC packet ACS should be disabled when
using normal DMA descriptors.

Fixes: 47dd7a540b8a0 ("net: add support for STMicroelectronics Ethernet controllers.")
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
@@ -24,6 +24,7 @@
 static void dwmac1000_core_init(struct mac_device_info *hw,
 				struct net_device *dev)
 {
+	struct stmmac_priv *priv = netdev_priv(dev);
 	void __iomem *ioaddr = hw->pcsr;
 	u32 value = readl(ioaddr + GMAC_CONTROL);
 	int mtu = dev->mtu;
@@ -35,7 +36,7 @@ static void dwmac1000_core_init(struct m
 	 * Broadcom tags can look like invalid LLC/SNAP packets and cause the
 	 * hardware to truncate packets on reception.
 	 */
-	if (netdev_uses_dsa(dev))
+	if (netdev_uses_dsa(dev) || !priv->plat->enh_desc)
 		value &= ~GMAC_CONTROL_ACS;
 
 	if (mtu > 1500)