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

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Date:   Fri, 6 Jan 2017 22:02:36 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Simon Horman <horms+renesas@...ge.net.au>,
        David Miller <davem@...emloft.net>
Cc:     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

Hello!

On 01/05/2017 01:43 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.
>
> Note, ravb_tx_free() is moved but not otherwise modified by this patch.
>
> Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@...esas.com>
> [simon: reworked]
> Signed-off-by: Simon Horman <horms+renesas@...ge.net.au>
> --
> v1 [Kazuya Mizuguchi]
>
> 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

    Not sure that was good idea (sorry)... ravb_tx_ring() only unmaps the 
transmitted buffers, while we need to unmap everything...

> * Reduce scope of new local variable
> ---
>  drivers/net/ethernet/renesas/ravb_main.c | 89 ++++++++++++++++++--------------
>  1 file changed, 51 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 92d7692c840d..1797c48e3176 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -179,6 +179,44 @@ 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)
> +{
> +	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]++) {
> +		entry = priv->dirty_tx[q] % (priv->num_tx_ring[q] *
> +					     NUM_TX_DESC);
> +		desc = &priv->tx_ring[q][entry];
> +		if (desc->die_dt != DT_FEMPTY)

    Here, it stop once an untransmitted buffer is encountered...

> +			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++;
> +			}
> +			free_num++;
> +		}
> +		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)
>  {
> @@ -207,6 +245,18 @@ static void ravb_ring_free(struct net_device *ndev, int q)
>  	priv->tx_align[q] = NULL;
>
>  	if (priv->rx_ring[q]) {
> +		for (i = 0; i < priv->num_rx_ring[q]; i++) {
> +			struct ravb_ex_rx_desc *rx_desc = &priv->rx_ring[q][i];
> +
> +			if (!dma_mapping_error(ndev->dev.parent,
> +					       rx_desc->dptr)) {

   You forgot le32_to_cpu() here, we can't use the raw descriptor fields.

> +				dma_unmap_single(ndev->dev.parent,
> +						 le32_to_cpu(rx_desc->dptr),
> +						 PKT_BUF_SZ,
> +						 DMA_FROM_DEVICE);
> +				rx_desc->ds_cc = cpu_to_le16(0);

    You don't check it anyway, not sure what that buys...

[...]

MBR, Sergei