brcmfmac: add host tx glomming support

New WiFi full dongle supports receiving chained packets in one command
through the SDIO bus. This patch adds the support on the host side to
send chained packets.
Reviewed-by: NHante Meuleman <meuleman@broadcom.com>
Reviewed-by: NPieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: NFranky Lin <frankyl@broadcom.com>
Signed-off-by: NArend van Spriel <arend@broadcom.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmfmac/dhd_sdio.c

@@ -32,6 +32,7 @@
 #include <linux/debugfs.h>
 #include <linux/vmalloc.h>
 #include <linux/platform_data/brcmfmac-sdio.h>
+#include <linux/moduleparam.h>
 #include <asm/unaligned.h>
 #include <defs.h>
 #include <brcmu_wifi.h>
@@ -110,6 +111,8 @@ struct rte_console {
 #define BRCMF_TXBOUND	20	/* Default for max tx frames in
 				 one scheduling */
 
+#define BRCMF_DEFAULT_TXGLOM_SIZE	32  /* max tx frames in glom chain */
+
 #define BRCMF_TXMINMAX	1	/* Max tx frames if rx still pending */
 
 #define MEMBLOCK	2048	/* Block size used for downloading
@@ -360,6 +363,8 @@ struct brcmf_sdio_hdrinfo {
 	u16 len_left;
 	u16 len_nxtfrm;
 	u8 dat_offset;
+	bool lastfrm;
+	u16 tail_pad;
 };
 
 /* misc chip info needed by some of the routines */
@@ -455,6 +460,8 @@ struct brcmf_sdio {
 	bool sleeping; /* SDIO bus sleeping */
 
 	u8 tx_hdrlen;		/* sdio bus header length for tx packet */
+	bool txglom;		/* host tx glomming enable flag */
+	struct sk_buff *txglom_sgpad;	/* scatter-gather padding buffer */
 };
 
 /* clkstate */
@@ -479,6 +486,10 @@ static const uint max_roundup = 512;
 
 #define ALIGNMENT  4
 
+static int brcmf_sdio_txglomsz = BRCMF_DEFAULT_TXGLOM_SIZE;
+module_param_named(txglomsz, brcmf_sdio_txglomsz, int, 0);
+MODULE_PARM_DESC(txglomsz, "maximum tx packet chain size [SDIO]");
+
 enum brcmf_sdio_frmtype {
 	BRCMF_SDIO_FT_NORMAL,
 	BRCMF_SDIO_FT_SUPER,
@@ -1102,10 +1113,18 @@ static void brcmf_sdbrcm_free_glom(struct brcmf_sdio *bus)
  * host and WiFi dongle which contains information needed for SDIO core and
  * firmware
  *
- * It consists of 2 parts: hw header and software header
+ * It consists of 3 parts: hardware header, hardware extension header and
+ * software header
  * hardware header (frame tag) - 4 bytes
  * Byte 0~1: Frame length
  * Byte 2~3: Checksum, bit-wise inverse of frame length
+ * hardware extension header - 8 bytes
+ * Tx glom mode only, N/A for Rx or normal Tx
+ * Byte 0~1: Packet length excluding hw frame tag
+ * Byte 2: Reserved
+ * Byte 3: Frame flags, bit 0: last frame indication
+ * Byte 4~5: Reserved
+ * Byte 6~7: Tail padding length
  * software header - 8 bytes
  * Byte 0: Rx/Tx sequence number
  * Byte 1: 4 MSB Channel number, 4 LSB arbitrary flag
@@ -1116,6 +1135,7 @@ static void brcmf_sdbrcm_free_glom(struct brcmf_sdio *bus)
  * Byte 6~7: Reserved
  */
 #define SDPCM_HWHDR_LEN			4
+#define SDPCM_HWEXT_LEN			8
 #define SDPCM_SWHDR_LEN			8
 #define SDPCM_HDRLEN			(SDPCM_HWHDR_LEN + SDPCM_SWHDR_LEN)
 /* software header */
@@ -1265,18 +1285,28 @@ static inline void brcmf_sdio_update_hwhdr(u8 *header, u16 frm_length)
 static void brcmf_sdio_hdpack(struct brcmf_sdio *bus, u8 *header,
 			      struct brcmf_sdio_hdrinfo *hd_info)
 {
-	u32 sw_header;
+	u32 hdrval;
+	u8 hdr_offset;
 
 	brcmf_sdio_update_hwhdr(header, hd_info->len);
-
-	sw_header = bus->tx_seq;
-	sw_header |= (hd_info->channel << SDPCM_CHANNEL_SHIFT) &
-		     SDPCM_CHANNEL_MASK;
-	sw_header |= (hd_info->dat_offset << SDPCM_DOFFSET_SHIFT) &
-		     SDPCM_DOFFSET_MASK;
-	*(((__le32 *)header) + 1) = cpu_to_le32(sw_header);
-	*(((__le32 *)header) + 2) = 0;
-	trace_brcmf_sdpcm_hdr(SDPCM_TX, header);
+	hdr_offset = SDPCM_HWHDR_LEN;
+
+	if (bus->txglom) {
+		hdrval = (hd_info->len - hdr_offset) | (hd_info->lastfrm << 24);
+		*((__le32 *)(header + hdr_offset)) = cpu_to_le32(hdrval);
+		hdrval = (u16)hd_info->tail_pad << 16;
+		*(((__le32 *)(header + hdr_offset)) + 1) = cpu_to_le32(hdrval);
+		hdr_offset += SDPCM_HWEXT_LEN;
+	}
+
+	hdrval = hd_info->seq_num;
+	hdrval |= (hd_info->channel << SDPCM_CHANNEL_SHIFT) &
+		  SDPCM_CHANNEL_MASK;
+	hdrval |= (hd_info->dat_offset << SDPCM_DOFFSET_SHIFT) &
+		  SDPCM_DOFFSET_MASK;
+	*((__le32 *)(header + hdr_offset)) = cpu_to_le32(hdrval);
+	*(((__le32 *)(header + hdr_offset)) + 1) = 0;
+	trace_brcmf_sdpcm_hdr(SDPCM_TX + !!(bus->txglom), header);
 }
 
 static u8 brcmf_sdbrcm_rxglom(struct brcmf_sdio *bus, u8 rxseq)
@@ -1876,6 +1906,34 @@ brcmf_sdbrcm_wait_event_wakeup(struct brcmf_sdio *bus)
 	return;
 }
 
+static int brcmf_sdio_txpkt_hdalign(struct brcmf_sdio *bus, struct sk_buff *pkt)
+{
+	u16 head_align, head_pad;
+	u8 *dat_buf;
+
+	/* SDIO ADMA requires at least 32 bit alignment */
+	head_align = 4;
+	if (bus->sdiodev->pdata && bus->sdiodev->pdata->sd_head_align > 4)
+		head_align = bus->sdiodev->pdata->sd_head_align;
+
+	dat_buf = (u8 *)(pkt->data);
+
+	/* Check head padding */
+	head_pad = ((unsigned long)dat_buf % head_align);
+	if (head_pad) {
+		if (skb_headroom(pkt) < head_pad) {
+			bus->sdiodev->bus_if->tx_realloc++;
+			head_pad = 0;
+			if (skb_cow(pkt, head_pad))
+				return -ENOMEM;
+		}
+		skb_push(pkt, head_pad);
+		dat_buf = (u8 *)(pkt->data);
+		memset(dat_buf, 0, head_pad + bus->tx_hdrlen);
+	}
+	return head_pad;
+}
+
 /**
  * struct brcmf_skbuff_cb reserves first two bytes in sk_buff::cb for
  * bus layer usage.
@@ -1885,16 +1943,18 @@ brcmf_sdbrcm_wait_event_wakeup(struct brcmf_sdio *bus)
 /* bit mask of data length chopped from the previous packet */
 #define ALIGN_SKB_CHOP_LEN_MASK	0x7fff
 
-static int brcmf_sdio_txpkt_prep_sg(struct brcmf_sdio_dev *sdiodev,
+static int brcmf_sdio_txpkt_prep_sg(struct brcmf_sdio *bus,
 				    struct sk_buff_head *pktq,
-				    struct sk_buff *pkt, uint chan)
+				    struct sk_buff *pkt, u16 total_len)
 {
+	struct brcmf_sdio_dev *sdiodev;
 	struct sk_buff *pkt_pad;
-	u16 tail_pad, tail_chop, sg_align;
+	u16 tail_pad, tail_chop, sg_align, chain_pad;
 	unsigned int blksize;
-	u8 *dat_buf;
-	int ntail;
+	bool lastfrm;
+	int ntail, ret;
 
+	sdiodev = bus->sdiodev;
 	blksize = sdiodev->func[SDIO_FUNC_2]->cur_blksize;
 	sg_align = 4;
 	if (sdiodev->pdata && sdiodev->pdata->sd_sgentry_align > 4)
@@ -1903,14 +1963,23 @@ static int brcmf_sdio_txpkt_prep_sg(struct brcmf_sdio_dev *sdiodev,
 	WARN_ON(blksize % sg_align);
 
 	/* Check tail padding */
-	pkt_pad = NULL;
+	lastfrm = skb_queue_is_last(pktq, pkt);
+	tail_pad = 0;
 	tail_chop = pkt->len % sg_align;
-	tail_pad = sg_align - tail_chop;
-	tail_pad += blksize - (pkt->len + tail_pad) % blksize;
+	if (tail_chop)
+		tail_pad = sg_align - tail_chop;
+	chain_pad = (total_len + tail_pad) % blksize;
+	if (lastfrm && chain_pad)
+		tail_pad += blksize - chain_pad;
 	if (skb_tailroom(pkt) < tail_pad && pkt->len > blksize) {
-		pkt_pad = brcmu_pkt_buf_get_skb(tail_pad + tail_chop);
+		pkt_pad = bus->txglom_sgpad;
+		if (pkt_pad == NULL)
+			  brcmu_pkt_buf_get_skb(tail_pad + tail_chop);
 		if (pkt_pad == NULL)
 			return -ENOMEM;
+		ret = brcmf_sdio_txpkt_hdalign(bus, pkt_pad);
+		if (unlikely(ret < 0))
+			return ret;
 		memcpy(pkt_pad->data,
 		       pkt->data + pkt->len - tail_chop,
 		       tail_chop);
@@ -1925,14 +1994,10 @@ static int brcmf_sdio_txpkt_prep_sg(struct brcmf_sdio_dev *sdiodev,
 				return -ENOMEM;
 		if (skb_linearize(pkt))
 			return -ENOMEM;
-		dat_buf = (u8 *)(pkt->data);
 		__skb_put(pkt, tail_pad);
 	}
 
-	if (pkt_pad)
-		return pkt->len + tail_chop;
-	else
-		return pkt->len - tail_pad;
+	return tail_pad;
 }
 
 /**
@@ -1951,58 +2016,66 @@ static int
 brcmf_sdio_txpkt_prep(struct brcmf_sdio *bus, struct sk_buff_head *pktq,
 		      uint chan)
 {
-	u16 head_pad, head_align;
+	u16 head_pad, total_len;
 	struct sk_buff *pkt_next;
-	u8 *dat_buf;
-	int err;
+	u8 txseq;
+	int ret;
 	struct brcmf_sdio_hdrinfo hd_info = {0};
 
-	/* SDIO ADMA requires at least 32 bit alignment */
-	head_align = 4;
-	if (bus->sdiodev->pdata && bus->sdiodev->pdata->sd_head_align > 4)
-		head_align = bus->sdiodev->pdata->sd_head_align;
+	txseq = bus->tx_seq;
+	total_len = 0;
+	skb_queue_walk(pktq, pkt_next) {
+		/* alignment packet inserted in previous
+		 * loop cycle can be skipped as it is
+		 * already properly aligned and does not
+		 * need an sdpcm header.
+		 */
+		if (*(u32 *)(pkt_next->cb) & ALIGN_SKB_FLAG)
+			continue;
 
-	pkt_next = pktq->next;
-	dat_buf = (u8 *)(pkt_next->data);
+		/* align packet data pointer */
+		ret = brcmf_sdio_txpkt_hdalign(bus, pkt_next);
+		if (ret < 0)
+			return ret;
+		head_pad = (u16)ret;
+		if (head_pad)
+			memset(pkt_next->data, 0, head_pad + bus->tx_hdrlen);
 
-	/* Check head padding */
-	head_pad = ((unsigned long)dat_buf % head_align);
-	if (head_pad) {
-		if (skb_headroom(pkt_next) < head_pad) {
-			bus->sdiodev->bus_if->tx_realloc++;
-			head_pad = 0;
-			if (skb_cow(pkt_next, head_pad))
-				return -ENOMEM;
-		}
-		skb_push(pkt_next, head_pad);
-		dat_buf = (u8 *)(pkt_next->data);
-		memset(dat_buf, 0, head_pad + bus->tx_hdrlen);
-	}
+		total_len += pkt_next->len;
 
-	if (bus->sdiodev->sg_support && pktq->qlen > 1) {
-		err = brcmf_sdio_txpkt_prep_sg(bus->sdiodev, pktq,
-					       pkt_next, chan);
-		if (err < 0)
-			return err;
-		hd_info.len = (u16)err;
-	} else {
 		hd_info.len = pkt_next->len;
-	}
-
-	hd_info.channel = chan;
-	hd_info.dat_offset = head_pad + bus->tx_hdrlen;
-
-	/* Now fill the header */
-	brcmf_sdio_hdpack(bus, dat_buf, &hd_info);
-
-	if (BRCMF_BYTES_ON() &&
-	    ((BRCMF_CTL_ON() && chan == SDPCM_CONTROL_CHANNEL) ||
-	     (BRCMF_DATA_ON() && chan != SDPCM_CONTROL_CHANNEL)))
-		brcmf_dbg_hex_dump(true, pkt_next, hd_info.len, "Tx Frame:\n");
-	else if (BRCMF_HDRS_ON())
-		brcmf_dbg_hex_dump(true, pkt_next, head_pad + bus->tx_hdrlen,
-				   "Tx Header:\n");
+		hd_info.lastfrm = skb_queue_is_last(pktq, pkt_next);
+		if (bus->txglom && pktq->qlen > 1) {
+			ret = brcmf_sdio_txpkt_prep_sg(bus, pktq,
+						       pkt_next, total_len);
+			if (ret < 0)
+				return ret;
+			hd_info.tail_pad = (u16)ret;
+			total_len += (u16)ret;
+		}
 
+		hd_info.channel = chan;
+		hd_info.dat_offset = head_pad + bus->tx_hdrlen;
+		hd_info.seq_num = txseq++;
+
+		/* Now fill the header */
+		brcmf_sdio_hdpack(bus, pkt_next->data, &hd_info);
+
+		if (BRCMF_BYTES_ON() &&
+		    ((BRCMF_CTL_ON() && chan == SDPCM_CONTROL_CHANNEL) ||
+		     (BRCMF_DATA_ON() && chan != SDPCM_CONTROL_CHANNEL)))
+			brcmf_dbg_hex_dump(true, pkt_next, hd_info.len,
+					   "Tx Frame:\n");
+		else if (BRCMF_HDRS_ON())
+			brcmf_dbg_hex_dump(true, pkt_next,
+					   head_pad + bus->tx_hdrlen,
+					   "Tx Header:\n");
+	}
+	/* Hardware length tag of the first packet should be total
+	 * length of the chain (including padding)
+	 */
+	if (bus->txglom)
+		brcmf_sdio_update_hwhdr(pktq->next->data, total_len);
 	return 0;
 }
 
@@ -2020,6 +2093,7 @@ brcmf_sdio_txpkt_postp(struct brcmf_sdio *bus, struct sk_buff_head *pktq)
 {
 	u8 *hdr;
 	u32 dat_offset;
+	u16 tail_pad;
 	u32 dummy_flags, chop_len;
 	struct sk_buff *pkt_next, *tmp, *pkt_prev;
 
@@ -2029,42 +2103,42 @@ brcmf_sdio_txpkt_postp(struct brcmf_sdio *bus, struct sk_buff_head *pktq)
 			chop_len = dummy_flags & ALIGN_SKB_CHOP_LEN_MASK;
 			if (chop_len) {
 				pkt_prev = pkt_next->prev;
-				memcpy(pkt_prev->data + pkt_prev->len,
-				       pkt_next->data, chop_len);
 				skb_put(pkt_prev, chop_len);
 			}
 			__skb_unlink(pkt_next, pktq);
 			brcmu_pkt_buf_free_skb(pkt_next);
 		} else {
-			hdr = pkt_next->data + SDPCM_HWHDR_LEN;
+			hdr = pkt_next->data + bus->tx_hdrlen - SDPCM_SWHDR_LEN;
 			dat_offset = le32_to_cpu(*(__le32 *)hdr);
 			dat_offset = (dat_offset & SDPCM_DOFFSET_MASK) >>
 				     SDPCM_DOFFSET_SHIFT;
 			skb_pull(pkt_next, dat_offset);
+			if (bus->txglom) {
+				tail_pad = le16_to_cpu(*(__le16 *)(hdr - 2));
+				skb_trim(pkt_next, pkt_next->len - tail_pad);
+			}
 		}
 	}
 }
 
 /* Writes a HW/SW header into the packet and sends it. */
 /* Assumes: (a) header space already there, (b) caller holds lock */
-static int brcmf_sdbrcm_txpkt(struct brcmf_sdio *bus, struct sk_buff *pkt,
+static int brcmf_sdbrcm_txpkt(struct brcmf_sdio *bus, struct sk_buff_head *pktq,
 			      uint chan)
 {
 	int ret;
 	int i;
-	struct sk_buff_head localq;
+	struct sk_buff *pkt_next, *tmp;
 
 	brcmf_dbg(TRACE, "Enter\n");
 
-	__skb_queue_head_init(&localq);
-	__skb_queue_tail(&localq, pkt);
-	ret = brcmf_sdio_txpkt_prep(bus, &localq, chan);
+	ret = brcmf_sdio_txpkt_prep(bus, pktq, chan);
 	if (ret)
 		goto done;
 
 	sdio_claim_host(bus->sdiodev->func[1]);
 	ret = brcmf_sdcard_send_pkt(bus->sdiodev, bus->sdiodev->sbwad,
-				    SDIO_FUNC_2, F2SYNC, &localq);
+				    SDIO_FUNC_2, F2SYNC, pktq);
 	bus->sdcnt.f2txdata++;
 
 	if (ret < 0) {
@@ -2088,42 +2162,56 @@ static int brcmf_sdbrcm_txpkt(struct brcmf_sdio *bus, struct sk_buff *pkt,
 			if ((hi == 0) && (lo == 0))
 				break;
 		}
-
 	}
 	sdio_release_host(bus->sdiodev->func[1]);
-	if (ret == 0)
-		bus->tx_seq = (bus->tx_seq + 1) % SDPCM_SEQ_WRAP;
 
 done:
-	brcmf_sdio_txpkt_postp(bus, &localq);
-	__skb_dequeue_tail(&localq);
-	brcmf_txcomplete(bus->sdiodev->dev, pkt, ret == 0);
+	brcmf_sdio_txpkt_postp(bus, pktq);
+	if (ret == 0)
+		bus->tx_seq = (bus->tx_seq + pktq->qlen) % SDPCM_SEQ_WRAP;
+	skb_queue_walk_safe(pktq, pkt_next, tmp) {
+		__skb_unlink(pkt_next, pktq);
+		brcmf_txcomplete(bus->sdiodev->dev, pkt_next, ret == 0);
+	}
 	return ret;
 }
 
 static uint brcmf_sdbrcm_sendfromq(struct brcmf_sdio *bus, uint maxframes)
 {
 	struct sk_buff *pkt;
+	struct sk_buff_head pktq;
 	u32 intstatus = 0;
-	int ret = 0, prec_out;
+	int ret = 0, prec_out, i;
 	uint cnt = 0;
-	u8 tx_prec_map;
+	u8 tx_prec_map, pkt_num;
 
 	brcmf_dbg(TRACE, "Enter\n");
 
 	tx_prec_map = ~bus->flowcontrol;
 
 	/* Send frames until the limit or some other event */
-	for (cnt = 0; (cnt < maxframes) && data_ok(bus); cnt++) {
+	for (cnt = 0; (cnt < maxframes) && data_ok(bus);) {
+		pkt_num = 1;
+		__skb_queue_head_init(&pktq);
+		if (bus->txglom)
+			pkt_num = min_t(u8, bus->tx_max - bus->tx_seq,
+					brcmf_sdio_txglomsz);
+		pkt_num = min_t(u32, pkt_num,
+				brcmu_pktq_mlen(&bus->txq, ~bus->flowcontrol));
 		spin_lock_bh(&bus->txqlock);
-		pkt = brcmu_pktq_mdeq(&bus->txq, tx_prec_map, &prec_out);
-		if (pkt == NULL) {
-			spin_unlock_bh(&bus->txqlock);
-			break;
+		for (i = 0; i < pkt_num; i++) {
+			pkt = brcmu_pktq_mdeq(&bus->txq, tx_prec_map,
+					      &prec_out);
+			if (pkt == NULL)
+				break;
+			__skb_queue_tail(&pktq, pkt);
 		}
 		spin_unlock_bh(&bus->txqlock);
+		if (i == 0)
+			break;
 
-		ret = brcmf_sdbrcm_txpkt(bus, pkt, SDPCM_DATA_CHANNEL);
+		ret = brcmf_sdbrcm_txpkt(bus, &pktq, SDPCM_DATA_CHANNEL);
+		cnt += i;
 
 		/* In poll mode, need to check for other events */
 		if (!bus->intr && cnt) {
@@ -2670,7 +2758,7 @@ static int
 brcmf_sdbrcm_bus_txctl(struct device *dev, unsigned char *msg, uint msglen)
 {
 	u8 *frame;
-	u16 len;
+	u16 len, pad;
 	uint retries = 0;
 	u8 doff = 0;
 	int ret = -1;
@@ -2697,13 +2785,15 @@ brcmf_sdbrcm_bus_txctl(struct device *dev, unsigned char *msg, uint msglen)
 	doff += bus->tx_hdrlen;
 
 	/* Round send length to next SDIO block */
+	pad = 0;
 	if (bus->roundup && bus->blocksize && (len > bus->blocksize)) {
-		u16 pad = bus->blocksize - (len % bus->blocksize);
-		if ((pad <= bus->roundup) && (pad < bus->blocksize))
-			len += pad;
+		pad = bus->blocksize - (len % bus->blocksize);
+		if ((pad > bus->roundup) || (pad >= bus->blocksize))
+			pad = 0;
 	} else if (len % BRCMF_SDALIGN) {
-		len += BRCMF_SDALIGN - (len % BRCMF_SDALIGN);
+		pad = BRCMF_SDALIGN - (len % BRCMF_SDALIGN);
 	}
+	len += pad;
 
 	/* Satisfy length-alignment requirements */
 	if (len & (ALIGNMENT - 1))
@@ -2719,8 +2809,16 @@ brcmf_sdbrcm_bus_txctl(struct device *dev, unsigned char *msg, uint msglen)
 	hd_info.len = (u16)msglen;
 	hd_info.channel = SDPCM_CONTROL_CHANNEL;
 	hd_info.dat_offset = doff;
+	hd_info.seq_num = bus->tx_seq;
+	if (bus->txglom) {
+		hd_info.lastfrm = true;
+		hd_info.tail_pad = pad;
+	}
 	brcmf_sdio_hdpack(bus, frame, &hd_info);
 
+	if (bus->txglom)
+		brcmf_sdio_update_hwhdr(frame, len);
+
 	if (!data_ok(bus)) {
 		brcmf_dbg(INFO, "No bus credit bus->tx_max %d, bus->tx_seq %d\n",
 			  bus->tx_max, bus->tx_seq);
@@ -3435,11 +3533,15 @@ static int brcmf_sdbrcm_bus_preinit(struct device *dev)
 	struct brcmf_bus *bus_if = dev_get_drvdata(dev);
 	struct brcmf_sdio_dev *sdiodev = bus_if->bus_priv.sdio;
 	struct brcmf_sdio *bus = sdiodev->bus;
+	uint pad_size;
 	u32 value;
 	u8 idx;
 	int err;
 
-	/* sdio bus core specific dcmd */
+	/* the commands below use the terms tx and rx from
+	 * a device perspective, ie. bus:txglom affects the
+	 * bus transfers from device to host.
+	 */
 	idx = brcmf_sdio_chip_getinfidx(bus->ci, BCMA_CORE_SDIO_DEV);
 	if (bus->ci->c_inf[idx].rev < 12) {
 		/* for sdio core rev < 12, disable txgloming */
@@ -3456,6 +3558,32 @@ static int brcmf_sdbrcm_bus_preinit(struct device *dev)
 		err = brcmf_iovar_data_set(dev, "bus:txglomalign", &value,
 					   sizeof(u32));
 	}
+
+	if (err < 0)
+		goto done;
+
+	bus->tx_hdrlen = SDPCM_HWHDR_LEN + SDPCM_SWHDR_LEN;
+	if (sdiodev->sg_support) {
+		bus->txglom = false;
+		value = 1;
+		pad_size = bus->sdiodev->func[2]->cur_blksize << 1;
+		bus->txglom_sgpad = brcmu_pkt_buf_get_skb(pad_size);
+		if (!bus->txglom_sgpad)
+			brcmf_err("allocating txglom padding skb failed, reduced performance\n");
+
+		err = brcmf_iovar_data_set(bus->sdiodev->dev, "bus:rxglom",
+					   &value, sizeof(u32));
+		if (err < 0) {
+			/* bus:rxglom is allowed to fail */
+			err = 0;
+		} else {
+			bus->txglom = true;
+			bus->tx_hdrlen += SDPCM_HWEXT_LEN;
+		}
+	}
+	brcmf_bus_add_txhdrlen(bus->sdiodev->dev, bus->tx_hdrlen);
+
+done:
 	return err;
 }
 
@@ -3929,6 +4057,7 @@ static void brcmf_sdbrcm_release(struct brcmf_sdio *bus)
 			brcmf_sdbrcm_release_dongle(bus);
 		}
 
+		brcmu_pkt_buf_free_skb(bus->txglom_sgpad);
 		brcmf_sdbrcm_release_malloc(bus);
 
 		kfree(bus);
@@ -4034,8 +4163,6 @@ void *brcmf_sdbrcm_probe(u32 regsva, struct brcmf_sdio_dev *sdiodev)
 	brcmf_sdio_debugfs_create(bus);
 	brcmf_dbg(INFO, "completed!!\n");
 
-	brcmf_bus_add_txhdrlen(bus->sdiodev->dev, bus->tx_hdrlen);
-
 	/* if firmware path present try to download and bring up bus */
 	ret = brcmf_bus_start(bus->sdiodev->dev);
 	if (ret != 0) {