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Shuffle the TX underrun to work the same way as the RX underrun,

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as suggested by YongHyeon PYUN.
This commit is contained in:
Tim Kientzle 2013-01-05 20:37:40 +00:00
parent 139dac05e2
commit d7631c7111
1 changed files with 9 additions and 23 deletions
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32
sys/arm/ti/cpsw/if_cpsw.c
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@ -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;
}