netdev - Re: [PATCH/RFC v2 net-next] ravb: unmap descriptors when freeing rings

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Date:   Thu, 12 Jan 2017 14:18:21 +0100
From:   Simon Horman <horms@...ge.net.au>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:     David Miller <davem@...emloft.net>,
        Magnus Damm <magnus.damm@...il.com>, netdev@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH/RFC v2 net-next] ravb: unmap descriptors when freeing
 rings

On Thu, Jan 12, 2017 at 03:03:05PM +0300, Sergei Shtylyov wrote:
> On 01/12/2017 12:11 PM, Simon Horman wrote:

...

> >>   Here, it stop once an untransmitted buffer is encountered...
> >
> >Yes, I see that now.
> >
> >I wonder if we should:
> >
> >a) paramatise ravb_tx_free() so it may either clear all transmitted buffers
> >   (current behaviour) or all buffers (new behaviour).
> >b) provide a different version of this loop in ravb_ring_free()
> >
> >What are your thoughts?
> 
>    I'm voting for (b).

Ok, something like this?

@@ -215,6 +225,30 @@ static void ravb_ring_free(struct net_device *ndev, int q)
 	}
 
 	if (priv->tx_ring[q]) {
+		for (; priv->cur_tx[q] - priv->dirty_tx[q] > 0; priv->dirty_tx[q]++) {
+			struct ravb_tx_desc *desc;
+			int entry;
+
+			entry = priv->dirty_tx[q] % (priv->num_tx_ring[q] *
+						     NUM_TX_DESC);
+			desc = &priv->tx_ring[q][entry];
+
+			/* Free the original skb. */
+			if (priv->tx_skb[q][entry / NUM_TX_DESC]) {
+				u32 size = le16_to_cpu(desc->ds_tagl) & TX_DS;
+
+				dma_unmap_single(ndev->dev.parent,
+						 le32_to_cpu(desc->dptr),
+						 size, DMA_TO_DEVICE);
+				/* Last packet descriptor? */
+				if (entry % NUM_TX_DESC == NUM_TX_DESC - 1) {
+					entry /= NUM_TX_DESC;
+					dev_kfree_skb_any(priv->tx_skb[q][entry]);
+					priv->tx_skb[q][entry] = NULL;
+				}
+			}
+		}
+
 		ring_size = sizeof(struct ravb_tx_desc) *
 			    (priv->num_tx_ring[q] * NUM_TX_DESC + 1);
 		dma_free_coherent(ndev->dev.parent, ring_size, priv->tx_ring[q],