| Message ID | 4967459D.3070207@openwrt.org |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Friday 09 January 2009 13:39:57 Felix Fietkau wrote: > --- a/drivers/net/b44.c > +++ b/drivers/net/b44.c > @@ -73,8 +73,8 @@ > (BP)->tx_cons - (BP)->tx_prod - TX_RING_GAP(BP)) > #define NEXT_TX(N) (((N) + 1) & (B44_TX_RING_SIZE - 1)) > > -#define RX_PKT_OFFSET 30 > -#define RX_PKT_BUF_SZ (1536 + RX_PKT_OFFSET + 64) > +#define RX_PKT_OFFSET (RX_HEADER_LEN + 2) > +#define RX_PKT_BUF_SZ (1536 + RX_PKT_OFFSET) > > /* minimum number of free TX descriptors required to wake up TX process */ > #define B44_TX_WAKEUP_THRESH (B44_TX_RING_SIZE / 4) > @@ -682,7 +682,6 @@ static int b44_alloc_rx_skb(struct b44 * > } > > rh = (struct rx_header *) skb->data; > - skb_reserve(skb, RX_PKT_OFFSET); Looks correct. > rh->len = 0; > rh->flags = 0; > @@ -693,13 +692,13 @@ static int b44_alloc_rx_skb(struct b44 * > if (src_map != NULL) > src_map->skb = NULL; > > - ctrl = (DESC_CTRL_LEN & (RX_PKT_BUF_SZ - RX_PKT_OFFSET)); > + ctrl = (DESC_CTRL_LEN & RX_PKT_BUF_SZ); Are you sure this is right? b43 has the same DMA engine, and we subtract the offset from the buffer size there. So we end up with the descriptor control field telling the space available for the frame payload. So I think the correct code would be ctrl = (DESC_CTRL_LEN & (RX_PKT_BUF_SZ - RX_PKT_OFFSET)); > if (dest_idx == (B44_RX_RING_SIZE - 1)) > ctrl |= DESC_CTRL_EOT; > > dp = &bp->rx_ring[dest_idx]; > dp->ctrl = cpu_to_le32(ctrl); > - dp->addr = cpu_to_le32((u32) mapping + RX_PKT_OFFSET + bp->dma_offset); > + dp->addr = cpu_to_le32((u32) mapping + bp->dma_offset); This looks correct.
Michael Buesch wrote: > On Friday 09 January 2009 13:39:57 Felix Fietkau wrote: >> --- a/drivers/net/b44.c >> +++ b/drivers/net/b44.c >> @@ -73,8 +73,8 @@ >> (BP)->tx_cons - (BP)->tx_prod - TX_RING_GAP(BP)) >> #define NEXT_TX(N) (((N) + 1) & (B44_TX_RING_SIZE - 1)) >> >> -#define RX_PKT_OFFSET 30 >> -#define RX_PKT_BUF_SZ (1536 + RX_PKT_OFFSET + 64) >> +#define RX_PKT_OFFSET (RX_HEADER_LEN + 2) >> +#define RX_PKT_BUF_SZ (1536 + RX_PKT_OFFSET) >> >> /* minimum number of free TX descriptors required to wake up TX process */ >> #define B44_TX_WAKEUP_THRESH (B44_TX_RING_SIZE / 4) >> @@ -682,7 +682,6 @@ static int b44_alloc_rx_skb(struct b44 * >> } >> >> rh = (struct rx_header *) skb->data; >> - skb_reserve(skb, RX_PKT_OFFSET); > > Looks correct. > >> rh->len = 0; >> rh->flags = 0; >> @@ -693,13 +692,13 @@ static int b44_alloc_rx_skb(struct b44 * >> if (src_map != NULL) >> src_map->skb = NULL; >> >> - ctrl = (DESC_CTRL_LEN & (RX_PKT_BUF_SZ - RX_PKT_OFFSET)); >> + ctrl = (DESC_CTRL_LEN & RX_PKT_BUF_SZ); > > Are you sure this is right? b43 has the same DMA engine, and we > subtract the offset from the buffer size there. So we end up with > the descriptor control field telling the space available for the frame payload. Quote from a Datasheet for the BCM5365 that I found online: "This field is the length, in bytes, of the data buffer associated with this descriptor. A descriptor with a BufCount value greater than 0x1000 causes a descriptor protocol error." I checked the public hnddma.c code and it also appears to not subtract the packet offset either, so I think my version is correct. - Felix -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Felix Fietkau <nbd@openwrt.org> Date: Fri, 09 Jan 2009 13:39:57 +0100 > Broadcom 4400 puts a header of configurable size (apparently needs > to be at least 28 bytes) in front of received packets. When handling > this, the previous code accidentally added the offset 30 *twice* for > the software and once for the hardware, thereby cancelling out the > IP alignment effect of the 30 byte padding and wasting an additional > 30 bytes of memory per packet. > > This patch fixes this problem and improves routing throughput by > about 30% on MIPS, where unaligned access is expensive. > > Signed-off-by: Felix Fietkau <nbd@openwrt.org> Applied. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- a/drivers/net/b44.c +++ b/drivers/net/b44.c @@ -73,8 +73,8 @@ (BP)->tx_cons - (BP)->tx_prod - TX_RING_GAP(BP)) #define NEXT_TX(N) (((N) + 1) & (B44_TX_RING_SIZE - 1)) -#define RX_PKT_OFFSET 30 -#define RX_PKT_BUF_SZ (1536 + RX_PKT_OFFSET + 64) +#define RX_PKT_OFFSET (RX_HEADER_LEN + 2) +#define RX_PKT_BUF_SZ (1536 + RX_PKT_OFFSET) /* minimum number of free TX descriptors required to wake up TX process */ #define B44_TX_WAKEUP_THRESH (B44_TX_RING_SIZE / 4) @@ -682,7 +682,6 @@ static int b44_alloc_rx_skb(struct b44 * } rh = (struct rx_header *) skb->data; - skb_reserve(skb, RX_PKT_OFFSET); rh->len = 0; rh->flags = 0; @@ -693,13 +692,13 @@ static int b44_alloc_rx_skb(struct b44 * if (src_map != NULL) src_map->skb = NULL; - ctrl = (DESC_CTRL_LEN & (RX_PKT_BUF_SZ - RX_PKT_OFFSET)); + ctrl = (DESC_CTRL_LEN & RX_PKT_BUF_SZ); if (dest_idx == (B44_RX_RING_SIZE - 1)) ctrl |= DESC_CTRL_EOT; dp = &bp->rx_ring[dest_idx]; dp->ctrl = cpu_to_le32(ctrl); - dp->addr = cpu_to_le32((u32) mapping + RX_PKT_OFFSET + bp->dma_offset); + dp->addr = cpu_to_le32((u32) mapping + bp->dma_offset); if (bp->flags & B44_FLAG_RX_RING_HACK) b44_sync_dma_desc_for_device(bp->sdev, bp->rx_ring_dma, @@ -809,8 +808,8 @@ static int b44_rx(struct b44 *bp, int bu ssb_dma_unmap_single(bp->sdev, map, skb_size, DMA_FROM_DEVICE); /* Leave out rx_header */ - skb_put(skb, len + RX_PKT_OFFSET); - skb_pull(skb, RX_PKT_OFFSET); + skb_put(skb, len + RX_PKT_OFFSET); + skb_pull(skb, RX_PKT_OFFSET); } else { struct sk_buff *copy_skb;
Broadcom 4400 puts a header of configurable size (apparently needs to be at least 28 bytes) in front of received packets. When handling this, the previous code accidentally added the offset 30 *twice* for the software and once for the hardware, thereby cancelling out the IP alignment effect of the 30 byte padding and wasting an additional 30 bytes of memory per packet. This patch fixes this problem and improves routing throughput by about 30% on MIPS, where unaligned access is expensive. Signed-off-by: Felix Fietkau <nbd@openwrt.org> --- Sorry about the line wrapping in the previous mail. Should be fixed now -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html