brcmsmac: Remove internal tx queue

The brcmsmac internal tx buffering is problematic. The amount of
buffering is excessive (228 packets in addition to the 256 slots in each
DMA ring), and frames may be dropped due to a lack of flow control.

This patch reworks the transmit code path to remove the internal
buffering. Frames are immediately handed off to the DMA support rather
than passing through an intermediate queue. Non-aggregate frames are
queued immediately into the tx rings, and aggregate frames are queued
temporarily in an AMPDU session until ready for transmit.

Transmit flow control is also added to avoid dropping packets when the
tx rings are full. Conceptually this is a separate change, but it's
included in this commit because removing the tx queue without adding
flow control could cause significant problems.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Tested-by: Daniel Wagner <wagi@monom.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 153 insertions, 36 deletions

diff --git a/drivers/net/wireless/brcm80211/brcmsmac/dma.c b/drivers/net/wireless/brcm80211/brcmsmac/dma.c
index 6444cf1a2eb..426b9a97716 100644
--- a/drivers/net/wireless/brcm80211/brcmsmac/dma.c
+++ b/drivers/net/wireless/brcm80211/brcmsmac/dma.c
@@ -19,12 +19,17 @@
 #include <linux/slab.h>
 #include <linux/delay.h>
 #include <linux/pci.h>
+#include <net/cfg80211.h>
+#include <net/mac80211.h>
 
 #include <brcmu_utils.h>
 #include <aiutils.h>
 #include "types.h"
+#include "main.h"
 #include "dma.h"
 #include "soc.h"
+#include "scb.h"
+#include "ampdu.h"
 
 /*
  * dma register field offset calculation
@@ -230,6 +235,9 @@ struct dma_info {
 	struct bcma_device *core;
 	struct device *dmadev;
 
+	/* session information for AMPDU */
+	struct brcms_ampdu_session ampdu_session;
+
 	bool dma64;	/* this dma engine is operating in 64-bit mode */
 	bool addrext;	/* this dma engine supports DmaExtendedAddrChanges */
 
@@ -564,12 +572,13 @@ static bool _dma_alloc(struct dma_info *di, uint direction)
 	return dma64_alloc(di, direction);
 }
 
-struct dma_pub *dma_attach(char *name, struct si_pub *sih,
-			   struct bcma_device *core,
+struct dma_pub *dma_attach(char *name, struct brcms_c_info *wlc,
 			   uint txregbase, uint rxregbase, uint ntxd, uint nrxd,
 			   uint rxbufsize, int rxextheadroom,
 			   uint nrxpost, uint rxoffset, uint *msg_level)
 {
+	struct si_pub *sih = wlc->hw->sih;
+	struct bcma_device *core = wlc->hw->d11core;
 	struct dma_info *di;
 	u8 rev = core->id.rev;
 	uint size;
@@ -714,6 +723,9 @@ struct dma_pub *dma_attach(char *name, struct si_pub *sih,
 		}
 	}
 
+	/* Initialize AMPDU session */
+	brcms_c_ampdu_reset_session(&di->ampdu_session, wlc);
+
 	DMA_TRACE("ddoffsetlow 0x%x ddoffsethigh 0x%x dataoffsetlow 0x%x dataoffsethigh 0x%x addrext %d\n",
 		  di->ddoffsetlow, di->ddoffsethigh,
 		  di->dataoffsetlow, di->dataoffsethigh,
@@ -1016,6 +1028,17 @@ static bool dma64_rxidle(struct dma_info *di)
 		 D64_RS0_CD_MASK));
 }
 
+static bool dma64_txidle(struct dma_info *di)
+{
+	if (di->ntxd == 0)
+		return true;
+
+	return ((bcma_read32(di->core,
+			     DMA64TXREGOFFS(di, status0)) & D64_XS0_CD_MASK) ==
+		(bcma_read32(di->core, DMA64TXREGOFFS(di, ptr)) &
+		 D64_XS0_CD_MASK));
+}
+
 /*
  * post receive buffers
  *  return false is refill failed completely and ring is empty this will stall
@@ -1264,50 +1287,25 @@ bool dma_rxreset(struct dma_pub *pub)
 	return status == D64_RS0_RS_DISABLED;
 }
 
-/* Update count of available tx descriptors based on current DMA state */
-static void dma_update_txavail(struct dma_info *di)
+static void dma_txenq(struct dma_info *di, struct sk_buff *p)
 {
-	/*
-	 * Available space is number of descriptors less the number of
-	 * active descriptors and the number of queued AMPDU frames.
-	 */
-	di->dma.txavail = di->ntxd - ntxdactive(di, di->txin, di->txout) - 1;
-}
-
-
-/*
- * !! tx entry routine
- * WARNING: call must check the return value for error.
- *   the error(toss frames) could be fatal and cause many subsequent hard
- *   to debug problems
- */
-int dma_txfast(struct dma_pub *pub, struct sk_buff *p, bool commit)
-{
-	struct dma_info *di = (struct dma_info *)pub;
 	unsigned char *data;
 	uint len;
 	u16 txout;
 	u32 flags = 0;
 	dma_addr_t pa;
 
-	DMA_TRACE("%s:\n", di->name);
-
 	txout = di->txout;
 
+	if (WARN_ON(nexttxd(di, txout) == di->txin))
+		return;
+
 	/*
 	 * obtain and initialize transmit descriptor entry.
 	 */
 	data = p->data;
 	len = p->len;
 
-	/* no use to transmit a zero length packet */
-	if (len == 0)
-		return 0;
-
-	/* return nonzero if out of tx descriptors */
-	if (nexttxd(di, txout) == di->txin)
-		goto outoftxd;
-
 	/* get physical address of buffer start */
 	pa = dma_map_single(di->dmadev, data, len, DMA_TO_DEVICE);
 
@@ -1329,15 +1327,106 @@ int dma_txfast(struct dma_pub *pub, struct sk_buff *p, bool commit)
 
 	/* bump the tx descriptor index */
 	di->txout = txout;
+}
 
-	/* kick the chip */
-	if (commit)
-		bcma_write32(di->core, DMA64TXREGOFFS(di, ptr),
-		      di->xmtptrbase + I2B(txout, struct dma64desc));
+static void ampdu_finalize(struct dma_info *di)
+{
+	struct brcms_ampdu_session *session = &di->ampdu_session;
+	struct sk_buff *p;
+
+	if (WARN_ON(skb_queue_empty(&session->skb_list)))
+		return;
+
+	brcms_c_ampdu_finalize(session);
+
+	while (!skb_queue_empty(&session->skb_list)) {
+		p = skb_dequeue(&session->skb_list);
+		dma_txenq(di, p);
+	}
+
+	bcma_write32(di->core, DMA64TXREGOFFS(di, ptr),
+		     di->xmtptrbase + I2B(di->txout, struct dma64desc));
+	brcms_c_ampdu_reset_session(session, session->wlc);
+}
+
+static void prep_ampdu_frame(struct dma_info *di, struct sk_buff *p)
+{
+	struct brcms_ampdu_session *session = &di->ampdu_session;
+	int ret;
+
+	ret = brcms_c_ampdu_add_frame(session, p);
+	if (ret == -ENOSPC) {
+		/*
+		 * AMPDU cannot accomodate this frame. Close out the in-
+		 * progress AMPDU session and start a new one.
+		 */
+		ampdu_finalize(di);
+		ret = brcms_c_ampdu_add_frame(session, p);
+	}
+
+	WARN_ON(ret);
+}
+
+/* Update count of available tx descriptors based on current DMA state */
+static void dma_update_txavail(struct dma_info *di)
+{
+	/*
+	 * Available space is number of descriptors less the number of
+	 * active descriptors and the number of queued AMPDU frames.
+	 */
+	di->dma.txavail = di->ntxd - ntxdactive(di, di->txin, di->txout) -
+			  skb_queue_len(&di->ampdu_session.skb_list) - 1;
+}
+
+/*
+ * !! tx entry routine
+ * WARNING: call must check the return value for error.
+ *   the error(toss frames) could be fatal and cause many subsequent hard
+ *   to debug problems
+ */
+int dma_txfast(struct brcms_c_info *wlc, struct dma_pub *pub,
+	       struct sk_buff *p)
+{
+	struct dma_info *di = (struct dma_info *)pub;
+	struct brcms_ampdu_session *session = &di->ampdu_session;
+	struct ieee80211_tx_info *tx_info;
+	bool is_ampdu;
+
+	DMA_TRACE("%s:\n", di->name);
+
+	/* no use to transmit a zero length packet */
+	if (p->len == 0)
+		return 0;
+
+	/* return nonzero if out of tx descriptors */
+	if (di->dma.txavail == 0 || nexttxd(di, di->txout) == di->txin)
+		goto outoftxd;
+
+	tx_info = IEEE80211_SKB_CB(p);
+	is_ampdu = tx_info->flags & IEEE80211_TX_CTL_AMPDU;
+	if (is_ampdu)
+		prep_ampdu_frame(di, p);
+	else
+		dma_txenq(di, p);
 
 	/* tx flow control */
 	dma_update_txavail(di);
 
+	/* kick the chip */
+	if (is_ampdu) {
+		/*
+		 * Start sending data if we've got a full AMPDU, there's
+		 * no more space in the DMA ring, or the ring isn't
+		 * currently transmitting.
+		 */
+		if (skb_queue_len(&session->skb_list) == session->max_ampdu_frames ||
+		    di->dma.txavail == 0 || dma64_txidle(di))
+			ampdu_finalize(di);
+	} else {
+		bcma_write32(di->core, DMA64TXREGOFFS(di, ptr),
+			     di->xmtptrbase + I2B(di->txout, struct dma64desc));
+	}
+
 	return 0;
 
  outoftxd:
@@ -1345,7 +1434,35 @@ int dma_txfast(struct dma_pub *pub, struct sk_buff *p, bool commit)
 	brcmu_pkt_buf_free_skb(p);
 	di->dma.txavail = 0;
 	di->dma.txnobuf++;
-	return -1;
+	return -ENOSPC;
+}
+
+void dma_txflush(struct dma_pub *pub)
+{
+	struct dma_info *di = (struct dma_info *)pub;
+	struct brcms_ampdu_session *session = &di->ampdu_session;
+
+	if (!skb_queue_empty(&session->skb_list))
+		ampdu_finalize(di);
+}
+
+int dma_txpending(struct dma_pub *pub)
+{
+	struct dma_info *di = (struct dma_info *)pub;
+	return ntxdactive(di, di->txin, di->txout);
+}
+
+/*
+ * If we have an active AMPDU session and are not transmitting,
+ * this function will force tx to start.
+ */
+void dma_kick_tx(struct dma_pub *pub)
+{
+	struct dma_info *di = (struct dma_info *)pub;
+	struct brcms_ampdu_session *session = &di->ampdu_session;
+
+	if (!skb_queue_empty(&session->skb_list) && dma64_txidle(di))
+		ampdu_finalize(di);
 }
 
 /*