Author: kientzle
Date: Sat Jan 5 20:37:40 2013
New Revision: 245070
URL: http://svnweb.freebsd.org/changeset/base/245070
Log:
Shuffle the TX underrun to work the same way as the RX underrun,
as suggested by YongHyeon PYUN.
Modified:
head/sys/arm/ti/cpsw/if_cpsw.c
Modified: head/sys/arm/ti/cpsw/if_cpsw.c
==============================================================================
--- head/sys/arm/ti/cpsw/if_cpsw.c Sat Jan 5 20:37:14 2013
(r245069)
+++ head/sys/arm/ti/cpsw/if_cpsw.c Sat Jan 5 20:37:40 2013
(r245070)
@@ -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_so
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;
}
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