wil6210: Align Rx frames on 4*n+2 by having SNAP

For the networking code and for hardware network accelerators,
it is better to have IP header 4*n aligned. On the other side,
DMA on Rx path require buffer to be aligned on 4*n as well.
Having 14 bytes of Ethernet header, these 2 alignment
requests are in contradiction.

To solve this, order hardware offload block to not remove
SNAP header. This adds extra 6 bytes between addresses and
ethertype, making it 20 bytes total. This way, both buffer and
IP header are 4*n aligned. Remaining is only to remove SNAP
by shifting addresses 6 bytes. This involves data copying, so
this feature should be disabled unless required by the platform.

Module parameter "rx_align_2" (bool, default - false)
introduced to control this feature. Feature is completely disabled
when parameter is false.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

4 files changed, 33 insertions, 3 deletions

diff --git a/drivers/net/wireless/ath/wil6210/txrx.c b/drivers/net/wireless/ath/wil6210/txrx.c
index 3feb86c47795..2453470bc191 100644
--- a/drivers/net/wireless/ath/wil6210/txrx.c
+++ b/drivers/net/wireless/ath/wil6210/txrx.c
@@ -33,6 +33,15 @@ module_param(rtap_include_phy_info, bool, S_IRUGO);
 MODULE_PARM_DESC(rtap_include_phy_info,
                  " Include PHY info in the radiotap header, default - no");
 
+bool rx_align_2;
+module_param(rx_align_2, bool, S_IRUGO);
+MODULE_PARM_DESC(rx_align_2, " align Rx buffers on 4*n+2, default - no");
+
+static inline uint wil_rx_snaplen(void)
+{
+        return rx_align_2 ? 6 : 0;
+}
+
 static inline int wil_vring_is_empty(struct vring *vring)
 {
         return vring->swhead == vring->swtail;
@@ -209,7 +218,7 @@ static int wil_vring_alloc_skb(struct wil6210_priv *wil, struct vring *vring,
                                u32 i, int headroom)
 {
         struct device *dev = wil_to_dev(wil);
-        unsigned int sz = mtu_max + ETH_HLEN;
+        unsigned int sz = mtu_max + ETH_HLEN + wil_rx_snaplen();
         struct vring_rx_desc dd, *d = ⅆ
         volatile struct vring_rx_desc *_d = &vring->va[i].rx;
         dma_addr_t pa;
@@ -365,7 +374,8 @@ static struct sk_buff *wil_vring_reap_rx(struct wil6210_priv *wil,
         struct vring_rx_desc *d;
         struct sk_buff *skb;
         dma_addr_t pa;
-        unsigned int sz = mtu_max + ETH_HLEN;
+        unsigned int snaplen = wil_rx_snaplen();
+        unsigned int sz = mtu_max + ETH_HLEN + snaplen;
         u16 dmalen;
         u8 ftype;
         int cid;
@@ -438,7 +448,7 @@ static struct sk_buff *wil_vring_reap_rx(struct wil6210_priv *wil,
                 return NULL;
         }
 
-        if (unlikely(skb->len < ETH_HLEN)) {
+        if (unlikely(skb->len < ETH_HLEN + snaplen)) {
                 wil_err(wil, "Short frame, len = %d\n", skb->len);
                 /* TODO: process it (i.e. BAR) */
                 kfree_skb(skb);
@@ -460,6 +470,17 @@ static struct sk_buff *wil_vring_reap_rx(struct wil6210_priv *wil,
                  */
         }
 
+        if (snaplen) {
+                /* Packet layout
+                 * +-------+-------+---------+------------+------+
+                 * | SA(6) | DA(6) | SNAP(6) | ETHTYPE(2) | DATA |
+                 * +-------+-------+---------+------------+------+
+                 * Need to remove SNAP, shifting SA and DA forward
+                 */
+                memmove(skb->data + snaplen, skb->data, 2 * ETH_ALEN);
+                skb_pull(skb, snaplen);
+        }
+
         return skb;
 }
 
diff --git a/drivers/net/wireless/ath/wil6210/wil6210.h b/drivers/net/wireless/ath/wil6210/wil6210.h
index c1a71ab75a0e..a6b096eb7dee 100644
--- a/drivers/net/wireless/ath/wil6210/wil6210.h
+++ b/drivers/net/wireless/ath/wil6210/wil6210.h
@@ -28,6 +28,7 @@ extern unsigned int mtu_max;
 extern unsigned short rx_ring_overflow_thrsh;
 extern int agg_wsize;
 extern u32 vring_idle_trsh;
+extern bool rx_align_2;
 
 #define WIL_NAME "wil6210"
 #define WIL_FW_NAME "wil6210.fw" /* code */
diff --git a/drivers/net/wireless/ath/wil6210/wmi.c b/drivers/net/wireless/ath/wil6210/wmi.c
index 021313524913..8c18a46582db 100644
--- a/drivers/net/wireless/ath/wil6210/wmi.c
+++ b/drivers/net/wireless/ath/wil6210/wmi.c
@@ -1109,6 +1109,11 @@ int wmi_rx_chain_add(struct wil6210_priv *wil, struct vring *vring)
                  */
                 cmd.l3_l4_ctrl |= (1 << L3_L4_CTRL_TCPIP_CHECKSUM_EN_POS);
         }
+
+        if (rx_align_2)
+                cmd.l2_802_3_offload_ctrl |=
+                                L2_802_3_OFFLOAD_CTRL_SNAP_KEEP_MSK;
+
         /* typical time for secure PCP is 840ms */
         rc = wmi_call(wil, WMI_CFG_RX_CHAIN_CMDID, &cmd, sizeof(cmd),
                       WMI_CFG_RX_CHAIN_DONE_EVENTID, &evt, sizeof(evt), 2000);
diff --git a/drivers/net/wireless/ath/wil6210/wmi.h b/drivers/net/wireless/ath/wil6210/wmi.h
index 8a4af613e191..0979650e675d 100644
--- a/drivers/net/wireless/ath/wil6210/wmi.h
+++ b/drivers/net/wireless/ath/wil6210/wmi.h
@@ -687,6 +687,9 @@ struct wmi_cfg_rx_chain_cmd {
         #define L2_802_3_OFFLOAD_CTRL_VLAN_TAG_INSERTION_POS (0)
         #define L2_802_3_OFFLOAD_CTRL_VLAN_TAG_INSERTION_LEN (1)
         #define L2_802_3_OFFLOAD_CTRL_VLAN_TAG_INSERTION_MSK (0x1)
+        #define L2_802_3_OFFLOAD_CTRL_SNAP_KEEP_POS (1)
+        #define L2_802_3_OFFLOAD_CTRL_SNAP_KEEP_LEN (1)
+        #define L2_802_3_OFFLOAD_CTRL_SNAP_KEEP_MSK (0x2)
         u8 l2_802_3_offload_ctrl;
 
         #define L2_NWIFI_OFFLOAD_CTRL_REMOVE_QOS_POS (0)