From 9b6c7883bd42f3a888318b9d300a6d0f648eccac Mon Sep 17 00:00:00 2001 From: kientzle Date: Sat, 5 Jan 2013 20:37:40 +0000 Subject: Shuffle the TX underrun to work the same way as the RX underrun, as suggested by YongHyeon PYUN. --- sys/arm/ti/cpsw/if_cpsw.c | 32 +++++++++----------------------- 1 file changed, 9 insertions(+), 23 deletions(-) (limited to 'sys/arm') diff --git a/sys/arm/ti/cpsw/if_cpsw.c b/sys/arm/ti/cpsw/if_cpsw.c index d08bf28..a47c131 100644 --- a/sys/arm/ti/cpsw/if_cpsw.c +++ b/sys/arm/ti/cpsw/if_cpsw.c @@ -716,26 +716,22 @@ cpsw_start_locked(struct ifnet *ifp) if (STAILQ_EMPTY(&newslots)) return; - /* Attach new segments to the hardware TX queue. */ + /* Attach the list of new buffers to the hardware TX queue. */ prev_slot = STAILQ_LAST(&sc->tx_active, cpsw_slot, next); first_new_slot = STAILQ_FIRST(&newslots); STAILQ_CONCAT(&sc->tx_active, &newslots); if (prev_slot == NULL) { /* Start the TX queue fresh. */ cpsw_write_4(CPSW_CPDMA_TX_HDP(0), - cpsw_cpdma_txbd_paddr(first_new_slot->index)); + cpsw_cpdma_txbd_paddr(first_new_slot->index)); } else { - /* Add packets to current queue. */ - /* Race: The hardware might have sent the last packet - * on the queue and stopped the transmitter just - * before we got here. In that case, this is a no-op, - * but it also means there's a TX interrupt waiting - * to be processed as soon as we release the lock here. - * That TX interrupt can detect and recover from this - * situation; see cpsw_intr_tx_locked. - */ + /* Add buffers to end of current queue. */ cpsw_cpdma_write_txbd_next(prev_slot->index, cpsw_cpdma_txbd_paddr(first_new_slot->index)); + /* If underrun, restart queue. */ + if (cpsw_cpdma_read_txbd_flags(prev_slot->index) & CPDMA_BD_EOQ) + cpsw_write_4(CPSW_CPDMA_TX_HDP(0), + cpsw_cpdma_txbd_paddr(first_new_slot->index)); } sc->tx_enqueues += enqueued; sc->tx_queued += enqueued; @@ -1091,14 +1087,10 @@ cpsw_fill_rx_queue_locked(struct cpsw_softc *sc) cpsw_write_4(CPSW_CPDMA_RX_HDP(0), cpsw_cpdma_rxbd_paddr(next_slot->index)); } else { - /* Extend an existing RX queue. */ + /* Add buffers to end of current queue. */ cpsw_cpdma_write_rxbd_next(prev_slot->index, cpsw_cpdma_rxbd_paddr(next_slot->index)); - /* XXX Order matters: Previous write must complete - before next read begins in order to avoid an - end-of-queue race. I think bus_write and bus_read have - sufficient barriers built-in to ensure this. XXX */ - /* If old RX queue was stopped, restart it. */ + /* If underrun, restart queue. */ if (cpsw_cpdma_read_rxbd_flags(prev_slot->index) & CPDMA_BD_EOQ) { cpsw_write_4(CPSW_CPDMA_RX_HDP(0), cpsw_cpdma_rxbd_paddr(next_slot->index)); @@ -1170,12 +1162,6 @@ cpsw_intr_tx_locked(void *arg) /* Tell hardware the last item we dequeued. */ cpsw_write_4(CPSW_CPDMA_TX_CP(0), cpsw_cpdma_txbd_paddr(last_slot->index)); - /* If transmitter stopped and there's more, restart it. */ - /* This resolves the race described in tx_start above. */ - if ((last_flags & CPDMA_BD_EOQ) && (slot != NULL)) { - cpsw_write_4(CPSW_CPDMA_TX_HDP(0), - cpsw_cpdma_txbd_paddr(slot->index)); - } sc->tx_retires += retires; sc->tx_queued -= retires; } -- cgit v1.1