From 06c2fe951d58cdf2cafb432a76415236c8f73328 Mon Sep 17 00:00:00 2001 From: Peter Crosthwaite Date: Tue, 3 Dec 2013 21:56:50 -0800 Subject: net/cadence_gem: Prefetch rx descriptors ASAP The real hardware prefetches rx buffer descriptors ASAP and potentially throws relevant interrupts following the fetch even in the absence of a received packet. Reported-by: Deepika Dhamija Signed-off-by: Peter Crosthwaite Message-id: 41629e35edfdb1f02f1e401f2c3d0e2e4c9e44b3.1386136219.git.peter.crosthwaite@xilinx.com Signed-off-by: Peter Maydell --- hw/net/cadence_gem.c | 62 +++++++++++++++++++++++++++++----------------------- 1 file changed, 35 insertions(+), 27 deletions(-) (limited to 'hw/net') diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c index 69ad87e919..6734a9d309 100644 --- a/hw/net/cadence_gem.c +++ b/hw/net/cadence_gem.c @@ -346,6 +346,8 @@ typedef struct GemState { uint32_t rx_desc_addr; uint32_t tx_desc_addr; + unsigned rx_desc[2]; + } GemState; /* The broadcast MAC address: 0xFFFFFFFFFFFF */ @@ -579,13 +581,30 @@ static int gem_mac_address_filter(GemState *s, const uint8_t *packet) return GEM_RX_REJECT; } +static void gem_get_rx_desc(GemState *s) +{ + DB_PRINT("read descriptor 0x%x\n", (unsigned)s->rx_desc_addr); + /* read current descriptor */ + cpu_physical_memory_read(s->rx_desc_addr, + (uint8_t *)s->rx_desc, sizeof(s->rx_desc)); + + /* Descriptor owned by software ? */ + if (rx_desc_get_ownership(s->rx_desc) == 1) { + DB_PRINT("descriptor 0x%x owned by sw.\n", + (unsigned)s->rx_desc_addr); + s->regs[GEM_RXSTATUS] |= GEM_RXSTATUS_NOBUF; + s->regs[GEM_ISR] |= GEM_INT_RXUSED & ~(s->regs[GEM_IMR]); + /* Handle interrupt consequences */ + gem_update_int_status(s); + } +} + /* * gem_receive: * Fit a packet handed to us by QEMU into the receive descriptor ring. */ static ssize_t gem_receive(NetClientState *nc, const uint8_t *buf, size_t size) { - unsigned desc[2]; GemState *s; unsigned rxbufsize, bytes_to_copy; unsigned rxbuf_offset; @@ -595,11 +614,6 @@ static ssize_t gem_receive(NetClientState *nc, const uint8_t *buf, size_t size) s = qemu_get_nic_opaque(nc); - /* Do nothing if receive is not enabled. */ - if (!gem_can_receive(nc)) { - return -1; - } - /* Is this destination MAC address "for us" ? */ if (gem_mac_address_filter(s, buf) == GEM_RX_REJECT) { return -1; @@ -667,53 +681,44 @@ static ssize_t gem_receive(NetClientState *nc, const uint8_t *buf, size_t size) DB_PRINT("config bufsize: %d packet size: %ld\n", rxbufsize, size); while (bytes_to_copy) { - DB_PRINT("read descriptor 0x%x\n", (unsigned)s->rx_desc_addr); - /* read current descriptor */ - cpu_physical_memory_read(s->rx_desc_addr, - (uint8_t *)&desc[0], sizeof(desc)); - - /* Descriptor owned by software ? */ - if (rx_desc_get_ownership(desc) == 1) { - DB_PRINT("descriptor 0x%x owned by sw.\n", - (unsigned)s->rx_desc_addr); - s->regs[GEM_RXSTATUS] |= GEM_RXSTATUS_NOBUF; - s->regs[GEM_ISR] |= GEM_INT_RXUSED & ~(s->regs[GEM_IMR]); - /* Handle interrupt consequences */ - gem_update_int_status(s); + /* Do nothing if receive is not enabled. */ + if (!gem_can_receive(nc)) { + assert(!first_desc); return -1; } DB_PRINT("copy %d bytes to 0x%x\n", MIN(bytes_to_copy, rxbufsize), - rx_desc_get_buffer(desc)); + rx_desc_get_buffer(s->rx_desc)); /* Copy packet data to emulated DMA buffer */ - cpu_physical_memory_write(rx_desc_get_buffer(desc) + rxbuf_offset, + cpu_physical_memory_write(rx_desc_get_buffer(s->rx_desc) + rxbuf_offset, rxbuf_ptr, MIN(bytes_to_copy, rxbufsize)); bytes_to_copy -= MIN(bytes_to_copy, rxbufsize); rxbuf_ptr += MIN(bytes_to_copy, rxbufsize); /* Update the descriptor. */ if (first_desc) { - rx_desc_set_sof(desc); + rx_desc_set_sof(s->rx_desc); first_desc = false; } if (bytes_to_copy == 0) { - rx_desc_set_eof(desc); - rx_desc_set_length(desc, size); + rx_desc_set_eof(s->rx_desc); + rx_desc_set_length(s->rx_desc, size); } - rx_desc_set_ownership(desc); + rx_desc_set_ownership(s->rx_desc); /* Descriptor write-back. */ cpu_physical_memory_write(s->rx_desc_addr, - (uint8_t *)&desc[0], sizeof(desc)); + (uint8_t *)s->rx_desc, sizeof(s->rx_desc)); /* Next descriptor */ - if (rx_desc_get_wrap(desc)) { + if (rx_desc_get_wrap(s->rx_desc)) { DB_PRINT("wrapping RX descriptor list\n"); s->rx_desc_addr = s->regs[GEM_RXQBASE]; } else { DB_PRINT("incrementing RX descriptor list\n"); s->rx_desc_addr += 8; } + gem_get_rx_desc(s); } /* Count it */ @@ -1053,6 +1058,9 @@ static void gem_write(void *opaque, hwaddr offset, uint64_t val, /* Handle register write side effects */ switch (offset) { case GEM_NWCTRL: + if (val & GEM_NWCTRL_RXENA) { + gem_get_rx_desc(s); + } if (val & GEM_NWCTRL_TXSTART) { gem_transmit(s); } -- cgit v1.2.1