From a9171c4fb570b9c6f65955de03d3e38d2e9b0fdf Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 13 May 2014 16:09:37 +0100 Subject: hw/net/stellaris_enet: Correctly implement the TR and THR registers Packet transmission for the stellaris ethernet controller can be triggered in one of two ways: * by setting a threshold value in the THR register; when the FIFO fill level reaches the threshold, the h/w starts transmitting. Software has to finish filling the FIFO before the transmit process completes to avoid a (silent) underrun * by software writing to the TR register to explicitly trigger transmission Since QEMU transmits packets instantaneously (from the guest's point of view), implement "transmit based on threshold" with our existing mechanism of "transmit as soon as we have the whole packet", with the additional wrinkle that we don't transmit if the packet size is below the specified threshold, and implement "transmit by specific request" properly. Signed-off-by: Peter Maydell Reviewed-by: Dr. David Alan Gilbert --- hw/net/stellaris_enet.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'hw/net/stellaris_enet.c') diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c index b99f93e732..2079fc691f 100644 --- a/hw/net/stellaris_enet.c +++ b/hw/net/stellaris_enet.c @@ -109,6 +109,15 @@ static inline bool stellaris_txpacket_complete(stellaris_enet_state *s) return s->tx_fifo_len >= framelen; } +/* Return true if the TX FIFO threshold is enabled and the FIFO + * has filled enough to reach it. + */ +static inline bool stellaris_tx_thr_reached(stellaris_enet_state *s) +{ + return (s->thr < 0x3f && + (s->tx_fifo_len >= 4 * (s->thr * 8 + 1))); +} + /* Send the packet currently in the TX FIFO */ static void stellaris_enet_send(stellaris_enet_state *s) { @@ -309,7 +318,7 @@ static void stellaris_enet_write(void *opaque, hwaddr offset, s->tx_fifo[s->tx_fifo_len++] = value >> 24; } - if (stellaris_txpacket_complete(s)) { + if (stellaris_tx_thr_reached(s) && stellaris_txpacket_complete(s)) { stellaris_enet_send(s); } break; @@ -338,9 +347,13 @@ static void stellaris_enet_write(void *opaque, hwaddr offset, case 0x2c: /* MTXD */ s->mtxd = value & 0xff; break; + case 0x38: /* TR */ + if (value & 1) { + stellaris_enet_send(s); + } + break; case 0x30: /* MRXD */ case 0x34: /* NP */ - case 0x38: /* TR */ /* Ignored. */ case 0x3c: /* Undocuented: Timestamp? */ /* Ignored. */ -- cgit v1.2.3