brcmfmac: add credit borrowing mechanism

The firmware provides credits to the driver per WMM-AC. When
only AC_BE are to be transmitted to the firmware the driver
may use credits from other priorities to send AC_BE packets
towards the firmware.

Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 87 insertions, 8 deletions

diff --git a/drivers/net/wireless/brcm80211/brcmfmac/fwsignal.c b/drivers/net/wireless/brcm80211/brcmfmac/fwsignal.c
index f9153b115dcf..5352dc1fdf3c 100644
--- a/drivers/net/wireless/brcm80211/brcmfmac/fwsignal.c
+++ b/drivers/net/wireless/brcm80211/brcmfmac/fwsignal.c
@@ -21,6 +21,7 @@
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/err.h>
+#include <linux/jiffies.h>
 #include <uapi/linux/nl80211.h>
 #include <net/cfg80211.h>
 
@@ -271,6 +272,9 @@ struct brcmf_skbuff_cb {
         brcmu_maskget32(txs, BRCMF_FWS_TXSTAT_ ## field ## _MASK, \
                         BRCMF_FWS_TXSTAT_ ## field ## _SHIFT)
 
+/* How long to defer borrowing in jiffies */
+#define BRCMF_FWS_BORROW_DEFER_PERIOD           (HZ / 10)
+
 /**
  * enum brcmf_fws_fifo - fifo indices used by dongle firmware.
  *
@@ -425,9 +429,11 @@ struct brcmf_fws_info {
         struct work_struct fws_dequeue_work;
         u32 fifo_enqpkt[BRCMF_FWS_FIFO_COUNT];
         int fifo_credit[BRCMF_FWS_FIFO_COUNT];
+        int credits_borrowed[BRCMF_FWS_FIFO_AC_VO + 1];
         int deq_node_pos[BRCMF_FWS_FIFO_COUNT];
         u32 fifo_credit_map;
         u32 fifo_delay_map;
+        unsigned long borrow_defer_timestamp;
 };
 
 /*
@@ -997,9 +1003,34 @@ static int brcmf_fws_request_indicate(struct brcmf_fws_info *fws, u8 type,
 static void brcmf_fws_return_credits(struct brcmf_fws_info *fws,
                                      u8 fifo, u8 credits)
 {
+        int lender_ac;
+        int *borrowed;
+        int *fifo_credit;
+
         if (!credits)
                 return;
 
+        if ((fifo == BRCMF_FWS_FIFO_AC_BE) &&
+            (fws->credits_borrowed[0])) {
+                for (lender_ac = BRCMF_FWS_FIFO_AC_VO; lender_ac >= 0;
+                     lender_ac--) {
+                        borrowed = &fws->credits_borrowed[lender_ac];
+                        if (*borrowed) {
+                                fws->fifo_credit_map |= (1 << lender_ac);
+                                fifo_credit = &fws->fifo_credit[lender_ac];
+                                if (*borrowed >= credits) {
+                                        *borrowed -= credits;
+                                        *fifo_credit += credits;
+                                        return;
+                                } else {
+                                        credits -= *borrowed;
+                                        *fifo_credit += *borrowed;
+                                        *borrowed = 0;
+                                }
+                        }
+                }
+        }
+
         fws->fifo_credit_map |= 1 << fifo;
         fws->fifo_credit[fifo] += credits;
 }
@@ -1658,6 +1689,26 @@ fail:
                 fws->stats.rollback_success++;
 }
 
+static int brcmf_fws_borrow_credit(struct brcmf_fws_info *fws)
+{
+        int lender_ac;
+
+        if (time_after(fws->borrow_defer_timestamp, jiffies))
+                return -ENAVAIL;
+
+        for (lender_ac = 0; lender_ac <= BRCMF_FWS_FIFO_AC_VO; lender_ac++) {
+                if (fws->fifo_credit[lender_ac]) {
+                        fws->credits_borrowed[lender_ac]++;
+                        fws->fifo_credit[lender_ac]--;
+                        if (fws->fifo_credit[lender_ac] == 0)
+                                fws->fifo_credit_map &= ~(1 << lender_ac);
+                        brcmf_dbg(TRACE, "borrow credit from: %d\n", lender_ac);
+                        return 0;
+                }
+        }
+        return -ENAVAIL;
+}
+
 static int brcmf_fws_consume_credit(struct brcmf_fws_info *fws, int fifo,
                                     struct sk_buff *skb)
 {
@@ -1691,8 +1742,17 @@ static int brcmf_fws_consume_credit(struct brcmf_fws_info *fws, int fifo,
                 return 0;
         }
 
+        if (fifo != BRCMF_FWS_FIFO_AC_BE)
+                fws->borrow_defer_timestamp = jiffies +
+                                              BRCMF_FWS_BORROW_DEFER_PERIOD;
+
         if (!(*credit)) {
-                brcmf_dbg(TRACE, "exit: credits depleted\n");
+                /* Try to borrow a credit from other queue */
+                if (fifo == BRCMF_FWS_FIFO_AC_BE &&
+                    brcmf_fws_borrow_credit(fws) == 0)
+                        return 0;
+
+                brcmf_dbg(TRACE, "exit: ac=%d, credits depleted\n", fifo);
                 return -ENAVAIL;
         }
         (*credit)--;
@@ -1741,6 +1801,7 @@ rollback:
 int brcmf_fws_process_skb(struct brcmf_if *ifp, struct sk_buff *skb)
 {
         struct brcmf_pub *drvr = ifp->drvr;
+        struct brcmf_fws_info *fws = drvr->fws;
         struct brcmf_skbuff_cb *skcb = brcmf_skbcb(skb);
         struct ethhdr *eh = (struct ethhdr *)(skb->data);
         ulong flags;
@@ -1755,7 +1816,7 @@ int brcmf_fws_process_skb(struct brcmf_if *ifp, struct sk_buff *skb)
         if (ntohs(eh->h_proto) == ETH_P_PAE)
                 atomic_inc(&ifp->pend_8021x_cnt);
 
-        if (!brcmf_fws_fc_active(drvr->fws)) {
+        if (!brcmf_fws_fc_active(fws)) {
                 /* If the protocol uses a data header, apply it */
                 brcmf_proto_hdrpush(drvr, ifp->ifidx, 0, skb);
 
@@ -1765,7 +1826,7 @@ int brcmf_fws_process_skb(struct brcmf_if *ifp, struct sk_buff *skb)
 
         /* set control buffer information */
         skcb->if_flags = 0;
-        skcb->mac = brcmf_fws_find_mac_desc(drvr->fws, ifp, eh->h_dest);
+        skcb->mac = brcmf_fws_find_mac_desc(fws, ifp, eh->h_dest);
         skcb->state = BRCMF_FWS_SKBSTATE_NEW;
         brcmf_skb_if_flags_set_field(skb, INDEX, ifp->ifidx);
         if (!multicast)
@@ -1777,15 +1838,17 @@ int brcmf_fws_process_skb(struct brcmf_if *ifp, struct sk_buff *skb)
 
         brcmf_fws_lock(drvr, flags);
         if (skcb->mac->suppressed ||
-            brcmf_fws_mac_desc_closed(drvr->fws, skcb->mac, fifo) ||
+            brcmf_fws_mac_desc_closed(fws, skcb->mac, fifo) ||
             brcmu_pktq_mlen(&skcb->mac->psq, 3 << (fifo * 2)) ||
             (!multicast &&
-             brcmf_fws_consume_credit(drvr->fws, fifo, skb) < 0)) {
+             brcmf_fws_consume_credit(fws, fifo, skb) < 0)) {
                 /* enqueue the packet in delayQ */
                 drvr->fws->fifo_delay_map |= 1 << fifo;
-                brcmf_fws_enq(drvr->fws, BRCMF_FWS_SKBSTATE_DELAYED, fifo, skb);
+                brcmf_fws_enq(fws, BRCMF_FWS_SKBSTATE_DELAYED, fifo, skb);
         } else {
-                brcmf_fws_commit_skb(drvr->fws, fifo, skb);
+                if (brcmf_fws_commit_skb(fws, fifo, skb))
+                        if (!multicast)
+                                brcmf_skb_pick_up_credit(fws, fifo, skb);
         }
         brcmf_fws_unlock(drvr, flags);
         return 0;
@@ -1858,7 +1921,23 @@ static void brcmf_fws_dequeue_worker(struct work_struct *worker)
                             BRCMF_SKB_IF_FLAGS_CREDITCHECK_MASK)
                                 credit++;
                 }
-                fws->fifo_credit[fifo] -= credit;
+                if ((fifo == BRCMF_FWS_FIFO_AC_BE) &&
+                    (credit == fws->fifo_credit[fifo])) {
+                        fws->fifo_credit[fifo] -= credit;
+                        while (brcmf_fws_borrow_credit(fws) == 0) {
+                                skb = brcmf_fws_deq(fws, fifo);
+                                if (!skb) {
+                                        brcmf_fws_return_credits(fws, fifo, 1);
+                                        break;
+                                }
+                                if (brcmf_fws_commit_skb(fws, fifo, skb)) {
+                                        brcmf_fws_return_credits(fws, fifo, 1);
+                                        break;
+                                }
+                        }
+                } else {
+                        fws->fifo_credit[fifo] -= credit;
+                }
         }
         brcmf_fws_unlock(fws->drvr, flags);
 }