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terminate the rx descriptor list with a self-linked entry

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so high phy error rates on a 5212 don't cause rx overruns
This commit is contained in:
Sam Leffler 2003-10-22 04:37:34 +00:00
parent d3c09dd7db
commit 04e22a026d
1 changed files with 21 additions and 3 deletions
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24
sys/dev/ath/if_ath.c
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@ -1544,9 +1544,23 @@ ath_rxbuf_init(struct ath_softc *sc, struct ath_buf *bf)
}
bus_dmamap_sync(sc->sc_dmat, bf->bf_dmamap, BUS_DMASYNC_PREREAD);
/* setup descriptors */
/*
* Setup descriptors. For receive we always terminate
* the descriptor list with a self-linked entry so we'll
* not get overrun under high load (as can happen with a
* 5212 when ANI processing enables PHY errors).
*
* To insure the last descriptor is self-linked we create
* each descriptor as self-linked and add it to the end. As
* each additional descriptor is added the previous self-linked
* entry is ``fixed'' naturally. This should be safe even
* if DMA is happening. When processing RX interrupts we
* never remove/process the last, self-linked, entry on the
* descriptor list. This insures the hardware always has
* someplace to write a new frame.
*/
ds = bf->bf_desc;
ds->ds_link = 0;
ds->ds_link = bf->bf_daddr; /* link to self */
ds->ds_data = bf->bf_segs[0].ds_addr;
ath_hal_setuprxdesc(ah, ds
, m->m_len /* buffer size */
@ -1584,12 +1598,16 @@ ath_rx_proc(void *arg, int npending)
if_printf(ifp, "ath_rx_proc: no buffer!\n");
break;
}
ds = bf->bf_desc;
if (ds->ds_link == bf->bf_daddr) {
/* NB: never process the self-linked entry at the end */
break;
}
m = bf->bf_m;
if (m == NULL) { /* NB: shouldn't happen */
if_printf(ifp, "ath_rx_proc: no mbuf!\n");
continue;
}
ds = bf->bf_desc;
status = ath_hal_rxprocdesc(ah, ds);
#ifdef AR_DEBUG
if (ath_debug > 1)