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brcmsmac: Remove internal tx queue
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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>
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Seth Forshee authored and John W. Linville committed Nov 20, 2012
1 parent 32d0f12 commit e041f65
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Showing 8 changed files with 316 additions and 558 deletions.
167 changes: 8 additions & 159 deletions drivers/net/wireless/brcm80211/brcmsmac/ampdu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -813,133 +813,6 @@ void brcms_c_ampdu_finalize(struct brcms_ampdu_session *session)
session->ampdu_len);
}

int
brcms_c_sendampdu(struct ampdu_info *ampdu, struct brcms_txq_info *qi,
struct sk_buff **pdu, int prec)
{
struct brcms_c_info *wlc;
struct sk_buff *p;
struct brcms_ampdu_session session;
int err = 0;
u8 tid;

uint count, fifo, seg_cnt = 0;
struct scb *scb;
struct scb_ampdu *scb_ampdu;
struct scb_ampdu_tid_ini *ini;
struct ieee80211_tx_info *tx_info;
u16 qlen;
struct wiphy *wiphy;

wlc = ampdu->wlc;
wiphy = wlc->wiphy;
p = *pdu;

tid = (u8) (p->priority);

scb = &wlc->pri_scb;
scb_ampdu = &scb->scb_ampdu;
ini = &scb_ampdu->ini[tid];

/* Let pressure continue to build ... */
qlen = pktq_plen(&qi->q, prec);
if (ini->tx_in_transit > 0 &&
qlen < min(scb_ampdu->max_pdu, ini->ba_wsize))
/* Collect multiple MPDU's to be sent in the next AMPDU */
return -EBUSY;

/* at this point we intend to transmit an AMPDU */
brcms_c_ampdu_reset_session(&session, wlc);

while (p) {
struct ieee80211_tx_rate *txrate;

tx_info = IEEE80211_SKB_CB(p);
txrate = tx_info->status.rates;

if (tx_info->flags & IEEE80211_TX_CTL_AMPDU) {
err = brcms_c_prep_pdu(wlc, p, &fifo);
} else {
wiphy_err(wiphy, "%s: AMPDU flag is off!\n", __func__);
*pdu = NULL;
err = 0;
break;
}

if (err) {
if (err == -EBUSY) {
wiphy_err(wiphy, "wl%d: sendampdu: "
"prep_xdu retry\n", wlc->pub->unit);
*pdu = p;
break;
}

/* error in the packet; reject it */
wiphy_err(wiphy, "wl%d: sendampdu: prep_xdu "
"rejected\n", wlc->pub->unit);
*pdu = NULL;
break;
}

err = brcms_c_ampdu_add_frame(&session, p);
if (err == -ENOSPC) {
/*
* No space for this packet in the AMPDU.
* Requeue packet and proceed;
*/
*pdu = p;
break;
} else if (err) {
/* Unexpected error; reject packet */
wiphy_err(wiphy, "wl%d: sendampdu: add_frame rejected",
wlc->pub->unit);
*pdu = NULL;
break;
}

seg_cnt += 1;

/*
* check to see if the next pkt is
* a candidate for aggregation
*/
p = pktq_ppeek(&qi->q, prec);
if (p) {
tx_info = IEEE80211_SKB_CB(p);
if (tx_info->flags & IEEE80211_TX_CTL_AMPDU) {
/*
* check if there are enough
* descriptors available
*/
if (*wlc->core->txavail[fifo] <= seg_cnt + 1) {
wiphy_err(wiphy, "%s: No fifo space "
"!!\n", __func__);
p = NULL;
continue;
}
/* next packet fit for aggregation so dequeue */
p = brcmu_pktq_pdeq(&qi->q, prec);
} else {
p = NULL;
}
}
} /* end while(p) */

count = skb_queue_len(&session.skb_list);
ini->tx_in_transit += count;

if (count) {
/* patch up first and last txh's */
brcms_c_ampdu_finalize(&session);

while ((p = skb_dequeue(&session.skb_list)) != NULL)
brcms_c_txfifo(wlc, fifo, p,
skb_queue_empty(&session.skb_list));
}
/* endif (count) */
return err;
}

static void
brcms_c_ampdu_rate_status(struct brcms_c_info *wlc,
struct ieee80211_tx_info *tx_info,
Expand Down Expand Up @@ -1113,9 +986,16 @@ brcms_c_ampdu_dotxstatus_complete(struct ampdu_info *ampdu, struct scb *scb,
/* either retransmit or send bar if ack not recd */
if (!ack_recd) {
if (retry && (ini->txretry[index] < (int)retry_limit)) {
int ret;
ini->txretry[index]++;
ini->tx_in_transit--;
brcms_c_txq_enq(wlc, scb, p);
ret = brcms_c_txfifo(wlc, queue, p);
/*
* We shouldn't be out of space in the DMA
* ring here since we're reinserting a frame
* that was just pulled out.
*/
WARN_ONCE(ret, "queue %d out of txds\n", queue);
} else {
/* Retry timeout */
ini->tx_in_transit--;
Expand All @@ -1142,12 +1022,9 @@ brcms_c_ampdu_dotxstatus_complete(struct ampdu_info *ampdu, struct scb *scb,

p = dma_getnexttxp(wlc->hw->di[queue], DMA_RANGE_TRANSMITTED);
}
brcms_c_send_q(wlc);

/* update rate state */
antselid = brcms_c_antsel_antsel2id(wlc->asi, mimoantsel);

brcms_c_txfifo_complete(wlc, queue);
}

void
Expand Down Expand Up @@ -1204,7 +1081,6 @@ brcms_c_ampdu_dotxstatus(struct ampdu_info *ampdu, struct scb *scb,
p = dma_getnexttxp(wlc->hw->di[queue],
DMA_RANGE_TRANSMITTED);
}
brcms_c_txfifo_complete(wlc, queue);
}
}

Expand Down Expand Up @@ -1243,23 +1119,6 @@ void brcms_c_ampdu_shm_upd(struct ampdu_info *ampdu)
}
}

/*
* callback function that helps flushing ampdu packets from a priority queue
*/
static bool cb_del_ampdu_pkt(struct sk_buff *mpdu, void *arg_a)
{
struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(mpdu);
struct cb_del_ampdu_pars *ampdu_pars =
(struct cb_del_ampdu_pars *)arg_a;
bool rc;

rc = tx_info->flags & IEEE80211_TX_CTL_AMPDU ? true : false;
rc = rc && (tx_info->rate_driver_data[0] == NULL || ampdu_pars->sta == NULL ||
tx_info->rate_driver_data[0] == ampdu_pars->sta);
rc = rc && ((u8)(mpdu->priority) == ampdu_pars->tid);
return rc;
}

/*
* callback function that helps invalidating ampdu packets in a DMA queue
*/
Expand All @@ -1280,15 +1139,5 @@ static void dma_cb_fn_ampdu(void *txi, void *arg_a)
void brcms_c_ampdu_flush(struct brcms_c_info *wlc,
struct ieee80211_sta *sta, u16 tid)
{
struct brcms_txq_info *qi = wlc->pkt_queue;
struct pktq *pq = &qi->q;
int prec;
struct cb_del_ampdu_pars ampdu_pars;

ampdu_pars.sta = sta;
ampdu_pars.tid = tid;
for (prec = 0; prec < pq->num_prec; prec++)
brcmu_pktq_pflush(pq, prec, true, cb_del_ampdu_pkt,
(void *)&ampdu_pars);
brcms_c_inval_dma_pkts(wlc->hw, sta, dma_cb_fn_ampdu);
}
3 changes: 0 additions & 3 deletions drivers/net/wireless/brcm80211/brcmsmac/ampdu.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -45,9 +45,6 @@ extern void brcms_c_ampdu_finalize(struct brcms_ampdu_session *session);

extern struct ampdu_info *brcms_c_ampdu_attach(struct brcms_c_info *wlc);
extern void brcms_c_ampdu_detach(struct ampdu_info *ampdu);
extern int brcms_c_sendampdu(struct ampdu_info *ampdu,
struct brcms_txq_info *qi,
struct sk_buff **aggp, int prec);
extern void brcms_c_ampdu_dotxstatus(struct ampdu_info *ampdu, struct scb *scb,
struct sk_buff *p, struct tx_status *txs);
extern void brcms_c_ampdu_macaddr_upd(struct brcms_c_info *wlc);
Expand Down
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