[PATCH/RFC v3 net] ravb: unmap descriptors when freeing rings

From: Kazuya Mizuguchi <redacted>

"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 <redacted>
[simon: reworked]
Signed-off-by: Simon Horman <redacted>
--
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 | 113 ++++++++++++++++++-------------
 1 file changed, 65 insertions(+), 48 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 89ac1e3f6175..57fe1411bb9d 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c

@@ -179,6 +179,51 @@ static struct mdiobb_ops bb_ops = {
 	.get_mdio_data = ravb_get_mdio_data,
 };
 
+enum ravb_tx_free_mode {
+	ravb_tx_free_all,
+	ravb_tx_free_txed_only,
+};
+
+/* Free TX skb function for AVB-IP */
+static int ravb_tx_free(struct net_device *ndev, int q,
+			enum ravb_tx_free_mode free_mode)
+{
+	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 (free_mode == ravb_tx_free_txed_only &&
+		    desc->die_dt != DT_FEMPTY)
+			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)
 {

@@ -194,19 +239,21 @@ static void ravb_ring_free(struct net_device *ndev, int q)
 	kfree(priv->rx_skb[q]);
 	priv->rx_skb[q] = NULL;
 
-	/* Free TX skb ringbuffer */
-	if (priv->tx_skb[q]) {
-		for (i = 0; i < priv->num_tx_ring[q]; i++)
-			dev_kfree_skb(priv->tx_skb[q][i]);
-	}
-	kfree(priv->tx_skb[q]);
-	priv->tx_skb[q] = NULL;
-
 	/* Free aligned TX buffers */
 	kfree(priv->tx_align[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 *desc = &priv->rx_ring[q][i];
+
+			if (!dma_mapping_error(ndev->dev.parent,
+					       le32_to_cpu(desc->dptr)))
+				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],

@@ -215,12 +262,19 @@ static void ravb_ring_free(struct net_device *ndev, int q)
 	}
 
 	if (priv->tx_ring[q]) {
+		ravb_tx_free(ndev, q, ravb_tx_free_all);
+
 		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],
 				  priv->tx_desc_dma[q]);
 		priv->tx_ring[q] = NULL;
 	}
+
+	/* Free TX skb ringbuffer.
+	 * SKBs are freed by ravb_tx_free() call above. */
+	kfree(priv->tx_skb[q]);
+	priv->tx_skb[q] = NULL;
 }
 
 /* Format skb and descriptor buffer for Ethernet AVB */

@@ -431,44 +485,6 @@ static int ravb_dmac_init(struct net_device *ndev)
 	return 0;
 }
 
-/* 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)
-			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;
-}
-
 static void ravb_get_tx_tstamp(struct net_device *ndev)
 {
 	struct ravb_private *priv = netdev_priv(ndev);

@@ -902,7 +918,7 @@ static int ravb_poll(struct napi_struct *napi, int budget)
 			spin_lock_irqsave(&priv->lock, flags);
 			/* Clear TX interrupt */
 			ravb_write(ndev, ~mask, TIS);
-			ravb_tx_free(ndev, q);
+			ravb_tx_free(ndev, q, ravb_tx_free_txed_only);
 			netif_wake_subqueue(ndev, q);
 			mmiowb();
 			spin_unlock_irqrestore(&priv->lock, flags);

@@ -1567,7 +1583,8 @@ static netdev_tx_t ravb_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 
 	priv->cur_tx[q] += NUM_TX_DESC;
 	if (priv->cur_tx[q] - priv->dirty_tx[q] >
-	    (priv->num_tx_ring[q] - 1) * NUM_TX_DESC && !ravb_tx_free(ndev, q))
+	    (priv->num_tx_ring[q] - 1) * NUM_TX_DESC &&
+	    !ravb_tx_free(ndev, q, ravb_tx_free_txed_only))
 		netif_stop_subqueue(ndev, q);
 
 exit:

-- 
2.7.0.rc3.207.g0ac5344

Hello.

On 01/24/2017 09:21 PM, Simon Horman wrote:

    Hmm... Sorry but this looks over-engineered. A *bool* parameter (named e.g 
'all) would suffice IMHO.

+{
+	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 (free_mode == ravb_tx_free_txed_only &&
+		    desc->die_dt != DT_FEMPTY)
+			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;

    Hmmm... we shouldn't count the discarded unsent packets/bytes as sent, right?

[...]

    This is not a recommended comment format:

/* bla
  * bla
  */

[...]

MBR, Sergei

On 01/24/2017 09:21 PM, Simon Horman wrote:

From: Kazuya Mizuguchi <redacted>

"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.

    Could you look into the sh_eth driver which seems to have the same issue?

Note, ravb_tx_free() is moved but not otherwise modified by this patch.

    This is not true anymore BTW.

Signed-off-by: Kazuya Mizuguchi <redacted>
[simon: reworked]
Signed-off-by: Simon Horman <redacted>

MBR, Sergei

On Wed, Jan 25, 2017 at 07:05:08PM +0300, Sergei Shtylyov wrote:

Hello.

On 01/24/2017 09:21 PM, Simon Horman wrote:

quoted

From: Kazuya Mizuguchi <redacted>

"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 <redacted>
[simon: reworked]
Signed-off-by: Simon Horman <redacted>
--
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 | 113 ++++++++++++++++++-------------
1 file changed, 65 insertions(+), 48 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 89ac1e3f6175..57fe1411bb9d 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c

@@ -179,6 +179,51 @@ static struct mdiobb_ops bb_ops = {

	.get_mdio_data = ravb_get_mdio_data,
};

+enum ravb_tx_free_mode {
+	ravb_tx_free_all,
+	ravb_tx_free_txed_only,
+};
+
+/* Free TX skb function for AVB-IP */
+static int ravb_tx_free(struct net_device *ndev, int q,
+			enum ravb_tx_free_mode free_mode)

   Hmm... Sorry but this looks over-engineered. A *bool* parameter (named
e.g 'all) would suffice IMHO.

Ha! The last time I used a bool for something like this I was encouraged
to use an enum, admittedly that was not kernel code but I was unsure
which way to go this time. I'll change things to bool as you sugget.

quoted

+{
+	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 (free_mode == ravb_tx_free_txed_only &&
+		    desc->die_dt != DT_FEMPTY)
+			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;

   Hmmm... we shouldn't count the discarded unsent packets/bytes as sent, right?

Yes, I think so. Sorry for missing that.

[...]

quoted

@@ -215,12 +262,19 @@ static void ravb_ring_free(struct net_device *ndev, int q)

	}

	if (priv->tx_ring[q]) {
+		ravb_tx_free(ndev, q, ravb_tx_free_all);
+
		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],
				  priv->tx_desc_dma[q]);
		priv->tx_ring[q] = NULL;
	}
+
+	/* Free TX skb ringbuffer.
+	 * SKBs are freed by ravb_tx_free() call above. */

   This is not a recommended comment format:

/* bla
 * bla
 */

Thanks, I will fix that.

On Wed, Jan 25, 2017 at 07:18:15PM +0300, Sergei Shtylyov wrote:

On 01/24/2017 09:21 PM, Simon Horman wrote:

quoted

From: Kazuya Mizuguchi <redacted>

"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.

   Could you look into the sh_eth driver which seems to have the same issue?

Sure, I will check.

quoted

Note, ravb_tx_free() is moved but not otherwise modified by this patch.

   This is not true anymore BTW.

Thanks for noticing, I'll fix that.

quoted

Signed-off-by: Kazuya Mizuguchi <redacted>
[simon: reworked]
Signed-off-by: Simon Horman <redacted>

MBR, Sergei

On Wed, Jan 25, 2017 at 5:18 PM, Sergei Shtylyov
[off-list ref] wrote:

On 01/24/2017 09:21 PM, Simon Horman wrote:

quoted

From: Kazuya Mizuguchi <redacted>

"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.

   Could you look into the sh_eth driver which seems to have the same issue?

Indeed, after a few suspend/resume cycles on r8a7791/koelsch:

WARNING: CPU: 1 PID: 1699 at lib/dma-debug.c:517 add_dma_entry+0xfc/0x148
DMA-API: exceeded 7 overlapping mappings of cacheline 0x0000000001a827e3

Gr{oetje,eeting}s,

                        Geert

On Fri, Feb 10, 2017 at 02:52:50PM +0100, Geert Uytterhoeven wrote:

On Wed, Jan 25, 2017 at 5:18 PM, Sergei Shtylyov
[off-list ref] wrote:

quoted

On 01/24/2017 09:21 PM, Simon Horman wrote:

quoted

From: Kazuya Mizuguchi <redacted>

"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.

   Could you look into the sh_eth driver which seems to have the same issue?

Indeed, after a few suspend/resume cycles on r8a7791/koelsch:

WARNING: CPU: 1 PID: 1699 at lib/dma-debug.c:517 add_dma_entry+0xfc/0x148
DMA-API: exceeded 7 overlapping mappings of cacheline 0x0000000001a827e3

Thanks for confirming that. It matches my expectation after
reading of the sh_eth code.