wcn36xx: Pad TIM PVM if needed

The wcn36xx FW expects a fixed size TIM PVM in the beacon template. If
supplied with a shorter than expected PVM it will overwrite the IE
following the TIM.

Squashed with fix from Jason Mobarak <jam@cozybit.com>:
Patch "wcn36xx: Pad TIM PVM if needed" has caused a regression in mesh
beaconing.  The field tim_off is always 0 for mesh mode, and thus
pvm_len (referring to the TIM length field) and pad are both incorrectly
calculated.  Thus, msg_body.beacon_length is incorrectly calculated for
mesh mode. Fix this.

Signed-off-by: Pontus Fuchs <pontus.fuchs@gmail.com>
Signed-off-by: Jason Mobarak <jam@cozybit.com>
[bjorn: squashed in Jason's fixup]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/wcn36xx/hal.h

@@ -54,6 +54,9 @@
 /* Default Beacon template size */
 #define BEACON_TEMPLATE_SIZE 0x180
 
+/* Minimum PVM size that the FW expects. See comment in smd.c for details. */
+#define TIM_MIN_PVM_SIZE 6
+
 /* Param Change Bitmap sent to HAL */
 #define PARAM_BCN_INTERVAL_CHANGED                      (1 << 0)
 #define PARAM_SHORT_PREAMBLE_CHANGED                 (1 << 1)

drivers/net/wireless/ath/wcn36xx/smd.c

@@ -1375,12 +1375,19 @@ int wcn36xx_smd_send_beacon(struct wcn36xx *wcn, struct ieee80211_vif *vif,
 			    u16 p2p_off)
 {
 	struct wcn36xx_hal_send_beacon_req_msg msg_body;
-	int ret = 0;
+	int ret = 0, pad, pvm_len;
 
 	mutex_lock(&wcn->hal_mutex);
 	INIT_HAL_MSG(msg_body, WCN36XX_HAL_SEND_BEACON_REQ);
 
-	msg_body.beacon_length = skb_beacon->len;
+	pvm_len = skb_beacon->data[tim_off + 1] - 3;
+	pad = TIM_MIN_PVM_SIZE - pvm_len;
+
+	/* Padding is irrelevant to mesh mode since tim_off is always 0. */
+	if (vif->type == NL80211_IFTYPE_MESH_POINT)
+		pad = 0;
+
+	msg_body.beacon_length = skb_beacon->len + pad;
 	/* TODO need to find out why + 6 is needed */
 	msg_body.beacon_length6 = msg_body.beacon_length + 6;
 
@@ -1393,6 +1400,22 @@ int wcn36xx_smd_send_beacon(struct wcn36xx *wcn, struct ieee80211_vif *vif,
 	memcpy(msg_body.beacon, skb_beacon->data, skb_beacon->len);
 	memcpy(msg_body.bssid, vif->addr, ETH_ALEN);
 
+	if (pad > 0) {
+		/*
+		 * The wcn36xx FW has a fixed size for the PVM in the TIM. If
+		 * given the beacon template from mac80211 with a PVM shorter
+		 * than the FW expectes it will overwrite the data after the
+		 * TIM.
+		 */
+		wcn36xx_dbg(WCN36XX_DBG_HAL, "Pad TIM PVM. %d bytes at %d\n",
+			    pad, pvm_len);
+		memmove(&msg_body.beacon[tim_off + 5 + pvm_len + pad],
+			&msg_body.beacon[tim_off + 5 + pvm_len],
+			skb_beacon->len - (tim_off + 5 + pvm_len));
+		memset(&msg_body.beacon[tim_off + 5 + pvm_len], 0, pad);
+		msg_body.beacon[tim_off + 1] += pad;
+	}
+
 	/* TODO need to find out why this is needed? */
 	if (vif->type == NL80211_IFTYPE_MESH_POINT)
 		/* mesh beacon don't need this, so push further down */