netdev - [PATCH net] net: stmmac: Disable ACS Feature for GMAC >= 4

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Message-Id: <1c69d3cabd8d26648c327d72a0a58d3d879cfc34.1524045087.git.joabreu@synopsys.com>
Date:   Wed, 18 Apr 2018 10:57:55 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     netdev@...r.kernel.org
Cc:     Jose Abreu <Jose.Abreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>
Subject: [PATCH net] net: stmmac: Disable ACS Feature for GMAC >= 4

ACS Feature is currently enabled for GMAC >= 4 but the llc_snap status
is never checked in descriptor rx_status callback. This will cause
stmmac to always strip packets even that ACS feature is already
stripping them.

Lets be safe and disable the ACS feature for GMAC >= 4 and always strip
the packets for this GMAC version.

Fixes: 477286b53f55 ("stmmac: add GMAC4 core support")
Signed-off-by: Jose Abreu <joabreu@...opsys.com>
Cc: David S. Miller <davem@...emloft.net>
Cc: Joao Pinto <jpinto@...opsys.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@...com>
Cc: Alexandre Torgue <alexandre.torgue@...com>
---
Hi David,

Requesting this to go up for stable also. I think its for v4.7+ but if you
could cross-check it would be great! Let me know if you need any more
info for queueing this.

Thanks
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4.h      |    2 +-
 drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c |    7 -------
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c |    7 ++++++-
 3 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
index c7bff59..dedd406 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
@@ -347,7 +347,7 @@ enum power_event {
 #define MTL_RX_OVERFLOW_INT		BIT(16)
 
 /* Default operating mode of the MAC */
-#define GMAC_CORE_INIT (GMAC_CONFIG_JD | GMAC_CONFIG_PS | GMAC_CONFIG_ACS | \
+#define GMAC_CORE_INIT (GMAC_CONFIG_JD | GMAC_CONFIG_PS | \
 			GMAC_CONFIG_BE | GMAC_CONFIG_DCRS)
 
 /* To dump the core regs excluding  the Address Registers */
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
index a3af92e..517b1f6 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
@@ -31,13 +31,6 @@ static void dwmac4_core_init(struct mac_device_info *hw,
 
 	value |= GMAC_CORE_INIT;
 
-	/* Clear ACS bit because Ethernet switch tagging formats such as
-	 * Broadcom tags can look like invalid LLC/SNAP packets and cause the
-	 * hardware to truncate packets on reception.
-	 */
-	if (netdev_uses_dsa(dev))
-		value &= ~GMAC_CONFIG_ACS;
-
 	if (mtu > 1500)
 		value |= GMAC_CONFIG_2K;
 	if (mtu > 2000)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 9a16931..b65e2d1 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3495,8 +3495,13 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 
 			/* ACS is set; GMAC core strips PAD/FCS for IEEE 802.3
 			 * Type frames (LLC/LLC-SNAP)
+			 *
+			 * llc_snap is never checked in GMAC >= 4, so this ACS
+			 * feature is always disabled and packets need to be
+			 * stripped manually.
 			 */
-			if (unlikely(status != llc_snap))
+			if (unlikely(priv->synopsys_id >= DWMAC_CORE_4_00) ||
+			    unlikely(status != llc_snap))
 				frame_len -= ETH_FCS_LEN;
 
 			if (netif_msg_rx_status(priv)) {
-- 
1.7.1