diff mbox series

[net-next,7/7] tsnep: Rework RX buffer allocation

Message ID 20220915203638.42917-8-gerhard@engleder-embedded.com
State New
Headers show
Series tsnep: multi queue support and some other improvements | expand

Commit Message

Gerhard Engleder Sept. 15, 2022, 8:36 p.m. UTC 
Try to refill RX queue continously instead of dropping frames if
allocation fails. This seems to be the more common pattern for network
drivers and makes future XDP support simpler.

Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
---
 drivers/net/ethernet/engleder/tsnep.h         |   2 +
 drivers/net/ethernet/engleder/tsnep_ethtool.c |   7 +
 drivers/net/ethernet/engleder/tsnep_main.c    | 143 ++++++++++--------
 3 files changed, 85 insertions(+), 67 deletions(-)

Comments

Gerhard Engleder Sept. 23, 2022, 7:33 p.m. UTC | #1 
On 22.09.22 03:01, Jakub Kicinski wrote:
> On Thu, 15 Sep 2022 22:36:37 +0200 Gerhard Engleder wrote:
>> Try to refill RX queue continously instead of dropping frames if
>> allocation fails. This seems to be the more common pattern for network
>> drivers and makes future XDP support simpler.
> 
> Is there anything preventing the queue from becoming completely empty
> and potentially never getting refilled?
> 
> The lazy refill usually comes with some form of a watchdog / periodic
> depletion check.

You are right, I need to improve that. I will remove that commit for
now and rework it.
diff mbox series

Patch

diff --git a/drivers/net/ethernet/engleder/tsnep.h b/drivers/net/ethernet/engleder/tsnep.h
index 09a723b827c7..48811f361523 100644
--- a/drivers/net/ethernet/engleder/tsnep.h
+++ b/drivers/net/ethernet/engleder/tsnep.h
@@ -110,6 +110,7 @@  struct tsnep_rx {
 	dma_addr_t page_dma[TSNEP_RING_PAGE_COUNT];
 
 	struct tsnep_rx_entry entry[TSNEP_RING_SIZE];
+	int write;
 	int read;
 	u32 owner_counter;
 	int increment_owner_counter;
@@ -119,6 +120,7 @@  struct tsnep_rx {
 	u32 bytes;
 	u32 dropped;
 	u32 multicast;
+	u32 alloc_failed;
 };
 
 struct tsnep_queue {
diff --git a/drivers/net/ethernet/engleder/tsnep_ethtool.c b/drivers/net/ethernet/engleder/tsnep_ethtool.c
index b9c4c45db052..8fb00fe2be8c 100644
--- a/drivers/net/ethernet/engleder/tsnep_ethtool.c
+++ b/drivers/net/ethernet/engleder/tsnep_ethtool.c
@@ -8,6 +8,7 @@  static const char tsnep_stats_strings[][ETH_GSTRING_LEN] = {
 	"rx_bytes",
 	"rx_dropped",
 	"rx_multicast",
+	"rx_alloc_failed",
 	"rx_phy_errors",
 	"rx_forwarded_phy_errors",
 	"rx_invalid_frame_errors",
@@ -21,6 +22,7 @@  struct tsnep_stats {
 	u64 rx_bytes;
 	u64 rx_dropped;
 	u64 rx_multicast;
+	u64 rx_alloc_failed;
 	u64 rx_phy_errors;
 	u64 rx_forwarded_phy_errors;
 	u64 rx_invalid_frame_errors;
@@ -36,6 +38,7 @@  static const char tsnep_rx_queue_stats_strings[][ETH_GSTRING_LEN] = {
 	"rx_%d_bytes",
 	"rx_%d_dropped",
 	"rx_%d_multicast",
+	"rx_%d_alloc_failed",
 	"rx_%d_no_descriptor_errors",
 	"rx_%d_buffer_too_small_errors",
 	"rx_%d_fifo_overflow_errors",
@@ -47,6 +50,7 @@  struct tsnep_rx_queue_stats {
 	u64 rx_bytes;
 	u64 rx_dropped;
 	u64 rx_multicast;
+	u64 rx_alloc_failed;
 	u64 rx_no_descriptor_errors;
 	u64 rx_buffer_too_small_errors;
 	u64 rx_fifo_overflow_errors;
@@ -178,6 +182,7 @@  static void tsnep_ethtool_get_ethtool_stats(struct net_device *netdev,
 		tsnep_stats.rx_bytes += adapter->rx[i].bytes;
 		tsnep_stats.rx_dropped += adapter->rx[i].dropped;
 		tsnep_stats.rx_multicast += adapter->rx[i].multicast;
+		tsnep_stats.rx_alloc_failed += adapter->rx[i].alloc_failed;
 	}
 	reg = ioread32(adapter->addr + ECM_STAT);
 	tsnep_stats.rx_phy_errors =
@@ -200,6 +205,8 @@  static void tsnep_ethtool_get_ethtool_stats(struct net_device *netdev,
 		tsnep_rx_queue_stats.rx_bytes = adapter->rx[i].bytes;
 		tsnep_rx_queue_stats.rx_dropped = adapter->rx[i].dropped;
 		tsnep_rx_queue_stats.rx_multicast = adapter->rx[i].multicast;
+		tsnep_rx_queue_stats.rx_alloc_failed =
+			adapter->rx[i].alloc_failed;
 		reg = ioread32(adapter->addr + TSNEP_QUEUE(i) +
 			       TSNEP_RX_STATISTIC);
 		tsnep_rx_queue_stats.rx_no_descriptor_errors =
diff --git a/drivers/net/ethernet/engleder/tsnep_main.c b/drivers/net/ethernet/engleder/tsnep_main.c
index 444a6c4a7be4..61e958cf9aee 100644
--- a/drivers/net/ethernet/engleder/tsnep_main.c
+++ b/drivers/net/ethernet/engleder/tsnep_main.c
@@ -608,23 +608,6 @@  static void tsnep_rx_ring_cleanup(struct tsnep_rx *rx)
 	}
 }
 
-static int tsnep_rx_alloc_buffer(struct tsnep_rx *rx,
-				 struct tsnep_rx_entry *entry)
-{
-	struct page *page;
-
-	page = page_pool_dev_alloc_pages(rx->page_pool);
-	if (unlikely(!page))
-		return -ENOMEM;
-
-	entry->page = page;
-	entry->len = TSNEP_MAX_RX_BUF_SIZE;
-	entry->dma = page_pool_get_dma_addr(entry->page);
-	entry->desc->rx = __cpu_to_le64(entry->dma + TSNEP_SKB_PAD);
-
-	return 0;
-}
-
 static int tsnep_rx_ring_init(struct tsnep_rx *rx)
 {
 	struct device *dmadev = rx->adapter->dmadev;
@@ -671,10 +654,6 @@  static int tsnep_rx_ring_init(struct tsnep_rx *rx)
 		entry = &rx->entry[i];
 		next_entry = &rx->entry[(i + 1) % TSNEP_RING_SIZE];
 		entry->desc->next = __cpu_to_le64(next_entry->desc_dma);
-
-		retval = tsnep_rx_alloc_buffer(rx, entry);
-		if (retval)
-			goto failed;
 	}
 
 	return 0;
@@ -684,6 +663,31 @@  static int tsnep_rx_ring_init(struct tsnep_rx *rx)
 	return retval;
 }
 
+static int tsnep_rx_desc_available(struct tsnep_rx *rx)
+{
+	if (rx->read <= rx->write)
+		return TSNEP_RING_SIZE - rx->write + rx->read - 1;
+	else
+		return rx->read - rx->write - 1;
+}
+
+static int tsnep_rx_alloc_buffer(struct tsnep_rx *rx, int index)
+{
+	struct tsnep_rx_entry *entry = &rx->entry[index];
+	struct page *page;
+
+	page = page_pool_dev_alloc_pages(rx->page_pool);
+	if (unlikely(!page))
+		return -ENOMEM;
+
+	entry->page = page;
+	entry->len = TSNEP_MAX_RX_BUF_SIZE;
+	entry->dma = page_pool_get_dma_addr(entry->page);
+	entry->desc->rx = __cpu_to_le64(entry->dma + TSNEP_SKB_PAD);
+
+	return 0;
+}
+
 static void tsnep_rx_activate(struct tsnep_rx *rx, int index)
 {
 	struct tsnep_rx_entry *entry = &rx->entry[index];
@@ -711,6 +715,40 @@  static void tsnep_rx_activate(struct tsnep_rx *rx, int index)
 	entry->desc->properties = __cpu_to_le32(entry->properties);
 }
 
+static void tsnep_rx_refill(struct tsnep_rx *rx)
+{
+	int count = tsnep_rx_desc_available(rx);
+	int index;
+	bool enable = false;
+	int i;
+	int retval;
+
+	for (i = 0; i < count; i++) {
+		index = (rx->write + i) % TSNEP_RING_SIZE;
+
+		retval = tsnep_rx_alloc_buffer(rx, index);
+		if (unlikely(retval)) {
+			rx->alloc_failed++;
+			break;
+		}
+
+		tsnep_rx_activate(rx, index);
+
+		enable = true;
+	}
+
+	if (enable) {
+		rx->write = (rx->write + i) % TSNEP_RING_SIZE;
+
+		/* descriptor properties shall be valid before hardware is
+		 * notified
+		 */
+		dma_wmb();
+
+		iowrite32(TSNEP_CONTROL_RX_ENABLE, rx->addr + TSNEP_CONTROL);
+	}
+}
+
 static struct sk_buff *tsnep_build_skb(struct tsnep_rx *rx, struct page *page,
 				       int length)
 {
@@ -749,15 +787,12 @@  static int tsnep_rx_poll(struct tsnep_rx *rx, struct napi_struct *napi,
 	int done = 0;
 	enum dma_data_direction dma_dir;
 	struct tsnep_rx_entry *entry;
-	struct page *page;
 	struct sk_buff *skb;
 	int length;
-	bool enable = false;
-	int retval;
 
 	dma_dir = page_pool_get_dma_dir(rx->page_pool);
 
-	while (likely(done < budget)) {
+	while (likely(done < budget) && (rx->read != rx->write)) {
 		entry = &rx->entry[rx->read];
 		if ((__le32_to_cpu(entry->desc_wb->properties) &
 		     TSNEP_DESC_OWNER_COUNTER_MASK) !=
@@ -774,49 +809,30 @@  static int tsnep_rx_poll(struct tsnep_rx *rx, struct napi_struct *napi,
 			 TSNEP_DESC_LENGTH_MASK;
 		dma_sync_single_range_for_cpu(dmadev, entry->dma, TSNEP_SKB_PAD,
 					      length, dma_dir);
-		page = entry->page;
 
-		/* forward skb only if allocation is successful, otherwise
-		 * page is reused and frame dropped
-		 */
-		retval = tsnep_rx_alloc_buffer(rx, entry);
-		if (!retval) {
-			skb = tsnep_build_skb(rx, page, length);
-			if (skb) {
-				page_pool_release_page(rx->page_pool, page);
-
-				rx->packets++;
-				rx->bytes += length -
-					     TSNEP_RX_INLINE_METADATA_SIZE;
-				if (skb->pkt_type == PACKET_MULTICAST)
-					rx->multicast++;
-
-				napi_gro_receive(napi, skb);
-			} else {
-				page_pool_recycle_direct(rx->page_pool, page);
-
-				rx->dropped++;
-			}
-			done++;
+		skb = tsnep_build_skb(rx, entry->page, length);
+		if (skb) {
+			page_pool_release_page(rx->page_pool, entry->page);
+
+			rx->packets++;
+			rx->bytes += length - TSNEP_RX_INLINE_METADATA_SIZE;
+			if (skb->pkt_type == PACKET_MULTICAST)
+				rx->multicast++;
+
+			napi_gro_receive(napi, skb);
 		} else {
+			page_pool_recycle_direct(rx->page_pool, entry->page);
+
 			rx->dropped++;
 		}
+		entry->page = NULL;
 
-		tsnep_rx_activate(rx, rx->read);
-
-		enable = true;
+		done++;
 
 		rx->read = (rx->read + 1) % TSNEP_RING_SIZE;
 	}
 
-	if (enable) {
-		/* descriptor properties shall be valid before hardware is
-		 * notified
-		 */
-		dma_wmb();
-
-		iowrite32(TSNEP_CONTROL_RX_ENABLE, rx->addr + TSNEP_CONTROL);
-	}
+	tsnep_rx_refill(rx);
 
 	return done;
 }
@@ -825,7 +841,6 @@  static int tsnep_rx_open(struct tsnep_adapter *adapter, void __iomem *addr,
 			 int queue_index, struct tsnep_rx *rx)
 {
 	dma_addr_t dma;
-	int i;
 	int retval;
 
 	memset(rx, 0, sizeof(*rx));
@@ -843,13 +858,7 @@  static int tsnep_rx_open(struct tsnep_adapter *adapter, void __iomem *addr,
 	rx->owner_counter = 1;
 	rx->increment_owner_counter = TSNEP_RING_SIZE - 1;
 
-	for (i = 0; i < TSNEP_RING_SIZE; i++)
-		tsnep_rx_activate(rx, i);
-
-	/* descriptor properties shall be valid before hardware is notified */
-	dma_wmb();
-
-	iowrite32(TSNEP_CONTROL_RX_ENABLE, rx->addr + TSNEP_CONTROL);
+	tsnep_rx_refill(rx);
 
 	return 0;
 }