Re: [PATCH net-next 1/5] ionic: clean up page handling code

[Shannon Nelson]

On 8/31/20 5:14 PM, David Miller wrote:

From: Shannon Nelson <snel...@pensando.io>
Date: Mon, 31 Aug 2020 16:35:54 -0700

@@ -100,6 +100,8 @@ static struct sk_buff *ionic_rx_frags(struct ionic_queue *q,
                frag_len = min(len, (u16)PAGE_SIZE);
                len -= frag_len;

+ dma_sync_single_for_cpu(dev, dma_unmap_addr(page_info, dma_addr),

+                                       len, DMA_FROM_DEVICE);
                dma_unmap_page(dev, dma_unmap_addr(page_info, dma_addr),
                               PAGE_SIZE, DMA_FROM_DEVICE);
                skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,

The unmap operation performs a sync, if necessary, for you.

That's the pattern of usage:

        map();
        device read/write memory
        unmap();

That's it, no more, no less.

The time to use sync is when you want to maintain the mapping and keep
using it.

Thanks, I'll drop that part.
sln