Messages in this thread | | | Subject | Packet retry optimization in drivers/net/arm/at91_ehter.c | Date | Tue, 5 Jan 2010 16:41:16 -0500 | From | "James Kosin" <> |
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Since, a AT91_EMAC_TUND only happens when the transmitter is unable to transfer the frame in time for a frame to be sent. It makes sense to RETRY the packet in this condition in the ISR. Or would this overcomplicate a simple task? ... see below ...
James
---- Attached code snippet ----
/* * MAC interrupt handler */ static irqreturn_t at91ether_interrupt(int irq, void *dev_id) { ...
if (intstatus & AT91_EMAC_TCOM) { /* Transmit complete */ /* The TCOM bit is set even if the transmission failed. */ if (intstatus & (AT91_EMAC_TUND | AT91_EMAC_RTRY)) dev->stats.tx_errors += 1;
if (lp->skb) { dev_kfree_skb_irq(lp->skb); lp->skb = NULL; dma_unmap_single(NULL, lp->skb_physaddr, lp->skb_length, DMA_TO_DEVICE); } netif_wake_queue(dev); } ...
---- Alternate approach ----
/* The TCOM bit is set even if the transmission failed. */ if (intstatus & (AT91_EMAC_TUND)) { /* Set address of the data in the Transmit Address register */ at91_emac_write(AT91_EMAC_TAR, lp->skb_physaddr); /* Set length of the packet in the Transmit Control register */ at91_emac_write(AT91_EMAC_TCR, skb->len); } else if (intstatus & (AT91_EMAC_RTRY)) dev->stats.tx_errors += 1;
... I do know there needs to be a bit more code then to handle the successful case below this; but, this is enough to understand what I am talking about. The UNDERRUN error should happen infrequently and in ideal circumstances not happen at all.
---- James Kosin
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