netdev - Re: [PATCH v4 net] ravb: unmap descriptors when freeing rings

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Message-ID: <20170126132423.GA1030@verge.net.au>
Date:   Thu, 26 Jan 2017 14:24:25 +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,
        Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
Subject: Re: [PATCH v4 net] ravb: unmap descriptors when freeing rings

On Thu, Jan 26, 2017 at 03:58:45PM +0300, Sergei Shtylyov wrote:
> On 01/26/2017 02:04 PM, Simon Horman wrote:
> 
> >From: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
> >
> >"swiotlb buffer is full" errors occur after repeated initialisation of a
> >device - f.e. suspend/resume or ip link set up/down. This is because memory
> >mapped using dma_map_single() in ravb_ring_format() and ravb_start_xmit()
> >is not released.  Resolve this problem by unmapping descriptors when
> >freeing rings.
> >
> >Fixes: a780893c89f6 ("ravb: unmap descriptors when freeing rings")
> 
>    No such SHA1 hash known and the summary is from this patch.

Sorry, it took the HEAD commit rather than a hash I should have provided
as an argument to git fixes:


[alias]
	fixes = log -1 --pretty=fixes
[core]
	abbrev = 12
[pretty]
	fixes = Fixes: %h (\"%s\")

What I wanted to say was:

Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")

> >Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
> >[simon: reworked]
> >Signed-off-by: Simon Horman <horms+renesas@...ge.net.au>
> >--
> >
> >On inspection it appears that a similar problem is also present in
> >the SH-Ethernet driver.
> >
> >v4 [Simon Horman]
> >* As suggested by Sergei Shtylyov
> >  - Use bool as type for new parameter to ravb_tx_free()
> >  - Clean up comment style
> >  - Only increment tx_bytes for transmitted skbs
> >
> >v3 [Simon Horman]
> >* As suggested by Sergei Shtylyov
> >  - consistently use le32_to_cpu(desc->dptr)
> >  - Do not clear desc->ds_cc as it is not used
> >* Paramatise ravb_tx_free() to allow it to free non-transmitted buffers
> >
> >v2 [Simon Horman]
> >* As suggested by Sergei Shtylyov
> >  - Use dma_mapping_error() and rx_desc->ds_cc when unmapping RX descriptors;
> >    this is consistent with the way that they are mapped
> >  - Use ravb_tx_free() to clear TX descriptors
> >* Reduce scope of new local variable
> >
> >v1 [Kazuya Mizuguchi]
> >---
> > drivers/net/ethernet/renesas/ravb_main.c | 111 ++++++++++++++++++-------------
> > 1 file changed, 63 insertions(+), 48 deletions(-)
> >
> >diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> >index 89ac1e3f6175..5d66ac721335 100644
> >--- a/drivers/net/ethernet/renesas/ravb_main.c
> >+++ b/drivers/net/ethernet/renesas/ravb_main.c
> >@@ -179,6 +179,48 @@ static struct mdiobb_ops bb_ops = {
> > 	.get_mdio_data = ravb_get_mdio_data,
> > };
> >
> >+/* Free TX skb function for AVB-IP */
> >+static int ravb_tx_free(struct net_device *ndev, int q, bool free_txed_only)
> >+{
> >+	struct ravb_private *priv = netdev_priv(ndev);
> >+	struct net_device_stats *stats = &priv->stats[q];
> >+	struct ravb_tx_desc *desc;
> >+	int free_num = 0;
> >+	int entry;
> >+	u32 size;
> >+
> >+	for (; priv->cur_tx[q] - priv->dirty_tx[q] > 0; priv->dirty_tx[q]++) {
> >+		bool txed;
> >+
> >+		entry = priv->dirty_tx[q] % (priv->num_tx_ring[q] *
> >+					     NUM_TX_DESC);
> >+		desc = &priv->tx_ring[q][entry];
> >+		txed = desc->die_dt == DT_FEMPTY;
> >+		if (free_txed_only && !txed)
> >+			break;
> >+		/* Descriptor type must be checked before all other reads */
> >+		dma_rmb();
> >+		size = le16_to_cpu(desc->ds_tagl) & TX_DS;
> >+		/* Free the original skb. */
> >+		if (priv->tx_skb[q][entry / NUM_TX_DESC]) {
> >+			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;
> >+				stats->tx_packets++;
> 
>    We're still incrementing the packet # even when the packet hasn't been sent...

Thanks, sorry for missing that.

> >+			}
> >+			free_num++;
> >+		}
> >+		if (!txed)
> 
>    Your logic is reversed! :-(

Oops.

> >+			stats->tx_bytes += size;
> >+		desc->die_dt = DT_EEMPTY;
> >+	}
> >+	return free_num;
> >+}
> >+
> > /* Free skb's and DMA buffers for Ethernet AVB */
> > static void ravb_ring_free(struct net_device *ndev, int q)
> > {
> >@@ -194,19 +236,21 @@ static void ravb_ring_free(struct net_device *ndev, int q)
> [...]
> >
> > 	if (priv->rx_ring[q]) {
> >+		for (i = 0; i < priv->num_rx_ring[q]; i++) {
> >+			struct ravb_ex_rx_desc *desc = &priv->rx_ring[q][i];
> >+
> >+			if (!dma_mapping_error(ndev->dev.parent,
> >+					       le32_to_cpu(desc->dptr)))
> 
>    I'd check for zero buffer length (that marks unmapped RX buffers) but
> this should be good too... it's just that the length check is shorter. :-)

I'm pretty sure you suggested the logic above at some point.
Lets keep it :)

> >+				dma_unmap_single(ndev->dev.parent,
> >+						 le32_to_cpu(desc->dptr),
> >+						 PKT_BUF_SZ,
> >+						 DMA_FROM_DEVICE);
> >+		}
> > 		ring_size = sizeof(struct ravb_ex_rx_desc) *
> > 			    (priv->num_rx_ring[q] + 1);
> > 		dma_free_coherent(ndev->dev.parent, ring_size, priv->rx_ring[q],
> [...]
> 
> MBR, Sergei
>