The Broadcom FullMAC firmware has a few ways of doing flow control. One

of those is a sequence number based window mechanism.  Essentially every
packet on the SDIO bus has a sequence number.  The chip records which
sequence number we used last and when it sends us replies, it tells us
the maximum sequence number it accepts.  This means we can calculate a
window of sequence numbers that we are allowed to use.  With this I no
longer overflow the chip's RX fifo and can do stable network transfers.

1 files changed, 22 insertions, 2 deletions

diff --git a/sys/dev/sdmmc/if_bwfm_sdio.c b/sys/dev/sdmmc/if_bwfm_sdio.c
index 10c402544e2..c19c63a25f4 100644
--- a/sys/dev/sdmmc/if_bwfm_sdio.c
+++ b/sys/dev/sdmmc/if_bwfm_sdio.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: if_bwfm_sdio.c,v 1.9 2018/05/16 14:10:26 patrick Exp $ */
+/* $OpenBSD: if_bwfm_sdio.c,v 1.10 2018/05/17 21:59:26 patrick Exp $ */
 /*
  * Copyright (c) 2010-2016 Broadcom Corporation
  * Copyright (c) 2016,2017 Patrick Wildt <patrick@blueri.se>
@@ -87,6 +87,7 @@ struct bwfm_sdio_softc {
 	struct bwfm_core	 *sc_cc;
 
 	uint8_t			  sc_tx_seq;
+	uint8_t			  sc_tx_max_seq;
 	char			 *sc_rxdata_buf;
 	struct mbuf_queue	  sc_txdata_queue;
 
@@ -134,6 +135,7 @@ int		 bwfm_sdio_buscore_prepare(struct bwfm_softc *);
 void		 bwfm_sdio_buscore_activate(struct bwfm_softc *, uint32_t);
 
 struct mbuf *	 bwfm_sdio_newbuf(void);
+int		 bwfm_sdio_tx_ok(struct bwfm_sdio_softc *);
 void		 bwfm_sdio_tx_ctrlframe(struct bwfm_sdio_softc *);
 void		 bwfm_sdio_tx_dataframe(struct bwfm_sdio_softc *);
 void		 bwfm_sdio_rx_frames(struct bwfm_sdio_softc *);
@@ -209,6 +211,7 @@ bwfm_sdio_attach(struct device *parent, struct device *self, void *aux)
 	task_set(&sc->sc_task, bwfm_sdio_task, sc);
 	mq_init(&sc->sc_txdata_queue, 16, IPL_SOFTNET);
 	sc->sc_rxdata_buf = malloc(64 * 1024, M_DEVBUF, M_WAITOK);
+	sc->sc_tx_seq = 0xff;
 
 	rw_assert_wrlock(&sf->sc->sc_lock);
 	sc->sc_lock = &sf->sc->sc_lock;
@@ -913,6 +916,13 @@ bwfm_sdio_newbuf(void)
 	return (m);
 }
 
+int
+bwfm_sdio_tx_ok(struct bwfm_sdio_softc *sc)
+{
+	return (uint8_t)(sc->sc_tx_max_seq - sc->sc_tx_seq) != 0 &&
+	    ((uint8_t)(sc->sc_tx_max_seq - sc->sc_tx_seq) & 0x80) == 0;
+}
+
 void
 bwfm_sdio_tx_ctrlframe(struct bwfm_sdio_softc *sc)
 {
@@ -922,6 +932,9 @@ bwfm_sdio_tx_ctrlframe(struct bwfm_sdio_softc *sc)
 	char *buf;
 	size_t len;
 
+	if (!bwfm_sdio_tx_ok(sc))
+		return;
+
 	TAILQ_FOREACH_SAFE(ctl, &sc->sc_sc.sc_bcdc_txctlq, next, tmp) {
 		TAILQ_REMOVE(&sc->sc_sc.sc_bcdc_txctlq, ctl, next);
 
@@ -958,8 +971,13 @@ bwfm_sdio_tx_dataframe(struct bwfm_sdio_softc *sc)
 	struct mbuf *m;
 	char *buf;
 	size_t len;
+	int i;
 
-	for (;;) {
+	if (!bwfm_sdio_tx_ok(sc))
+		return;
+
+	i = min((uint8_t)(sc->sc_tx_max_seq - sc->sc_tx_seq), 32);
+	while (i--) {
 		m = mq_dequeue(&sc->sc_txdata_queue);
 		if (m == NULL)
 			break;
@@ -1034,6 +1052,8 @@ bwfm_sdio_rx_frames(struct bwfm_sdio_softc *sc)
 		    sizeof(swhdr), 0))
 			break;
 
+		sc->sc_tx_max_seq = swhdr.maxseqnr;
+
 		flen = hwhdr.frmlen - (sizeof(hwhdr) + sizeof(swhdr));
 		if (flen == 0)
 			continue;