net: mvpp2: Add TCAM entry to drop flow control pause frames

Issue:
Flow control frame used to pause GoP(MAC) was delivered to the CPU
and created a load on the CPU. Since XOFF/XON frames are used only
by MAC, these frames should be dropped inside MAC.

Fix:
According to 802.3-2012 - IEEE Standard for Ethernet pause frame
has unique destination MAC address 01-80-C2-00-00-01.
Add TCAM parser entry to track and drop pause frames by destination MAC.

Fixes: 3f518509 ("ethernet: Add new driver for Marvell Armada 375 network unit")
Signed-off-by: Stefan Chulski <stefanc@marvell.com>
Link: https://lore.kernel.org/r/1608229817-21951-1-git-send-email-stefanc@marvell.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/marvell/mvpp2/mvpp2_prs.c

@@ -405,6 +405,38 @@ static int mvpp2_prs_tcam_first_free(struct mvpp2 *priv, unsigned char start,
 	return -EINVAL;
 }
 
+/* Drop flow control pause frames */
+static void mvpp2_prs_drop_fc(struct mvpp2 *priv)
+{
+	unsigned char da[ETH_ALEN] = { 0x01, 0x80, 0xC2, 0x00, 0x00, 0x01 };
+	struct mvpp2_prs_entry pe;
+	unsigned int len;
+
+	memset(&pe, 0, sizeof(pe));
+
+	/* For all ports - drop flow control frames */
+	pe.index = MVPP2_PE_FC_DROP;
+	mvpp2_prs_tcam_lu_set(&pe, MVPP2_PRS_LU_MAC);
+
+	/* Set match on DA */
+	len = ETH_ALEN;
+	while (len--)
+		mvpp2_prs_tcam_data_byte_set(&pe, len, da[len], 0xff);
+
+	mvpp2_prs_sram_ri_update(&pe, MVPP2_PRS_RI_DROP_MASK,
+				 MVPP2_PRS_RI_DROP_MASK);
+
+	mvpp2_prs_sram_bits_set(&pe, MVPP2_PRS_SRAM_LU_GEN_BIT, 1);
+	mvpp2_prs_sram_next_lu_set(&pe, MVPP2_PRS_LU_FLOWS);
+
+	/* Mask all ports */
+	mvpp2_prs_tcam_port_map_set(&pe, MVPP2_PRS_PORT_MASK);
+
+	/* Update shadow table and hw entry */
+	mvpp2_prs_shadow_set(priv, pe.index, MVPP2_PRS_LU_MAC);
+	mvpp2_prs_hw_write(priv, &pe);
+}
+
 /* Enable/disable dropping all mac da's */
 static void mvpp2_prs_mac_drop_all_set(struct mvpp2 *priv, int port, bool add)
 {
@@ -1162,6 +1194,7 @@ static void mvpp2_prs_mac_init(struct mvpp2 *priv)
 	mvpp2_prs_hw_write(priv, &pe);
 
 	/* Create dummy entries for drop all and promiscuous modes */
+	mvpp2_prs_drop_fc(priv);
 	mvpp2_prs_mac_drop_all_set(priv, 0, false);
 	mvpp2_prs_mac_promisc_set(priv, 0, MVPP2_PRS_L2_UNI_CAST, false);
 	mvpp2_prs_mac_promisc_set(priv, 0, MVPP2_PRS_L2_MULTI_CAST, false);

drivers/net/ethernet/marvell/mvpp2/mvpp2_prs.h

@@ -129,7 +129,7 @@
 #define MVPP2_PE_VID_EDSA_FLTR_DEFAULT	(MVPP2_PRS_TCAM_SRAM_SIZE - 7)
 #define MVPP2_PE_VLAN_DBL		(MVPP2_PRS_TCAM_SRAM_SIZE - 6)
 #define MVPP2_PE_VLAN_NONE		(MVPP2_PRS_TCAM_SRAM_SIZE - 5)
-/* reserved */
+#define MVPP2_PE_FC_DROP		(MVPP2_PRS_TCAM_SRAM_SIZE - 4)
 #define MVPP2_PE_MAC_MC_PROMISCUOUS	(MVPP2_PRS_TCAM_SRAM_SIZE - 3)
 #define MVPP2_PE_MAC_UC_PROMISCUOUS	(MVPP2_PRS_TCAM_SRAM_SIZE - 2)
 #define MVPP2_PE_MAC_NON_PROMISCUOUS	(MVPP2_PRS_TCAM_SRAM_SIZE - 1)