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Message-ID: <20251119135330.551835-2-pvalerio@redhat.com>
Date: Wed, 19 Nov 2025 14:53:25 +0100
From: Paolo Valerio <pvalerio@...hat.com>
To: netdev@...r.kernel.org
Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>,
Claudiu Beznea <claudiu.beznea@...on.dev>,
Andrew Lunn <andrew+netdev@...n.ch>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Lorenzo Bianconi <lorenzo@...nel.org>
Subject: [PATCH RFC net-next 1/6] cadence: macb/gem: Add page pool support
Use the page pool allocator for the data buffers and enable skb recycling
support, instead of relying on netdev_alloc_skb allocating the entire skb
during the refill.
The change replaces the rx_skbuff array with rx_buff array to store page
pool allocated buffers instead of pre-allocated skbs. DMA mapping, rx and
refill path were updated accordingly.
Signed-off-by: Paolo Valerio <pvalerio@...hat.com>
---
drivers/net/ethernet/cadence/Kconfig | 1 +
drivers/net/ethernet/cadence/macb.h | 10 +-
drivers/net/ethernet/cadence/macb_main.c | 169 +++++++++++++++--------
3 files changed, 121 insertions(+), 59 deletions(-)
diff --git a/drivers/net/ethernet/cadence/Kconfig b/drivers/net/ethernet/cadence/Kconfig
index 5b2a461dfd28..ae500f717433 100644
--- a/drivers/net/ethernet/cadence/Kconfig
+++ b/drivers/net/ethernet/cadence/Kconfig
@@ -25,6 +25,7 @@ config MACB
depends on PTP_1588_CLOCK_OPTIONAL
select PHYLINK
select CRC32
+ select PAGE_POOL
help
The Cadence MACB ethernet interface is found on many Atmel AT32 and
AT91 parts. This driver also supports the Cadence GEM (Gigabit
diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
index 87414a2ddf6e..dcf768bd1bc1 100644
--- a/drivers/net/ethernet/cadence/macb.h
+++ b/drivers/net/ethernet/cadence/macb.h
@@ -14,6 +14,8 @@
#include <linux/interrupt.h>
#include <linux/phy/phy.h>
#include <linux/workqueue.h>
+#include <net/page_pool/helpers.h>
+#include <net/xdp.h>
#define MACB_GREGS_NBR 16
#define MACB_GREGS_VERSION 2
@@ -957,6 +959,10 @@ struct macb_dma_desc_ptp {
/* Scaled PPM fraction */
#define PPM_FRACTION 16
+/* The buf includes headroom compatible with both skb and xdpf */
+#define MACB_PP_HEADROOM XDP_PACKET_HEADROOM
+#define MACB_PP_MAX_BUF_SIZE(num) (((num) * PAGE_SIZE) - MACB_PP_HEADROOM)
+
/* struct macb_tx_skb - data about an skb which is being transmitted
* @skb: skb currently being transmitted, only set for the last buffer
* of the frame
@@ -1262,10 +1268,11 @@ struct macb_queue {
unsigned int rx_tail;
unsigned int rx_prepared_head;
struct macb_dma_desc *rx_ring;
- struct sk_buff **rx_skbuff;
+ void **rx_buff;
void *rx_buffers;
struct napi_struct napi_rx;
struct queue_stats stats;
+ struct page_pool *page_pool;
};
struct ethtool_rx_fs_item {
@@ -1289,6 +1296,7 @@ struct macb {
struct macb_dma_desc *rx_ring_tieoff;
dma_addr_t rx_ring_tieoff_dma;
size_t rx_buffer_size;
+ u16 rx_offset;
unsigned int rx_ring_size;
unsigned int tx_ring_size;
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index e461f5072884..985c81913ba6 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -1250,11 +1250,28 @@ static int macb_tx_complete(struct macb_queue *queue, int budget)
return packets;
}
-static void gem_rx_refill(struct macb_queue *queue)
+static void *gem_page_pool_get_buff(struct page_pool *pool,
+ dma_addr_t *dma_addr, gfp_t gfp_mask)
+{
+ struct page *page;
+
+ if (!pool)
+ return NULL;
+
+ page = page_pool_alloc_pages(pool, gfp_mask | __GFP_NOWARN);
+ if (!page)
+ return NULL;
+
+ *dma_addr = page_pool_get_dma_addr(page) + MACB_PP_HEADROOM;
+
+ return page_address(page);
+}
+
+static void gem_rx_refill(struct macb_queue *queue, bool napi)
{
unsigned int entry;
- struct sk_buff *skb;
dma_addr_t paddr;
+ void *data;
struct macb *bp = queue->bp;
struct macb_dma_desc *desc;
@@ -1267,25 +1284,17 @@ static void gem_rx_refill(struct macb_queue *queue)
desc = macb_rx_desc(queue, entry);
- if (!queue->rx_skbuff[entry]) {
+ if (!queue->rx_buff[entry]) {
/* allocate sk_buff for this free entry in ring */
- skb = netdev_alloc_skb(bp->dev, bp->rx_buffer_size);
- if (unlikely(!skb)) {
+ data = gem_page_pool_get_buff(queue->page_pool, &paddr,
+ napi ? GFP_ATOMIC : GFP_KERNEL);
+ if (unlikely(!data)) {
netdev_err(bp->dev,
- "Unable to allocate sk_buff\n");
+ "Unable to allocate page\n");
break;
}
- /* now fill corresponding descriptor entry */
- paddr = dma_map_single(&bp->pdev->dev, skb->data,
- bp->rx_buffer_size,
- DMA_FROM_DEVICE);
- if (dma_mapping_error(&bp->pdev->dev, paddr)) {
- dev_kfree_skb(skb);
- break;
- }
-
- queue->rx_skbuff[entry] = skb;
+ queue->rx_buff[entry] = data;
if (entry == bp->rx_ring_size - 1)
paddr |= MACB_BIT(RX_WRAP);
@@ -1295,20 +1304,6 @@ static void gem_rx_refill(struct macb_queue *queue)
*/
dma_wmb();
macb_set_addr(bp, desc, paddr);
-
- /* Properly align Ethernet header.
- *
- * Hardware can add dummy bytes if asked using the RBOF
- * field inside the NCFGR register. That feature isn't
- * available if hardware is RSC capable.
- *
- * We cannot fallback to doing the 2-byte shift before
- * DMA mapping because the address field does not allow
- * setting the low 2/3 bits.
- * It is 3 bits if HW_DMA_CAP_PTP, else 2 bits.
- */
- if (!(bp->caps & MACB_CAPS_RSC))
- skb_reserve(skb, NET_IP_ALIGN);
} else {
desc->ctrl = 0;
dma_wmb();
@@ -1349,12 +1344,16 @@ static int gem_rx(struct macb_queue *queue, struct napi_struct *napi,
int budget)
{
struct macb *bp = queue->bp;
+ int buffer_size;
unsigned int len;
unsigned int entry;
+ void *data;
struct sk_buff *skb;
struct macb_dma_desc *desc;
int count = 0;
+ buffer_size = DIV_ROUND_UP(bp->rx_buffer_size, PAGE_SIZE) * PAGE_SIZE;
+
while (count < budget) {
u32 ctrl;
dma_addr_t addr;
@@ -1387,24 +1386,49 @@ static int gem_rx(struct macb_queue *queue, struct napi_struct *napi,
queue->stats.rx_dropped++;
break;
}
- skb = queue->rx_skbuff[entry];
- if (unlikely(!skb)) {
+ data = queue->rx_buff[entry];
+ if (unlikely(!data)) {
netdev_err(bp->dev,
"inconsistent Rx descriptor chain\n");
bp->dev->stats.rx_dropped++;
queue->stats.rx_dropped++;
break;
}
+
+ skb = napi_build_skb(data, buffer_size);
+ if (unlikely(!skb)) {
+ netdev_err(bp->dev,
+ "Unable to allocate sk_buff\n");
+ page_pool_put_full_page(queue->page_pool,
+ virt_to_head_page(data),
+ false);
+ break;
+ }
+
+ /* Properly align Ethernet header.
+ *
+ * Hardware can add dummy bytes if asked using the RBOF
+ * field inside the NCFGR register. That feature isn't
+ * available if hardware is RSC capable.
+ *
+ * We cannot fallback to doing the 2-byte shift before
+ * DMA mapping because the address field does not allow
+ * setting the low 2/3 bits.
+ * It is 3 bits if HW_DMA_CAP_PTP, else 2 bits.
+ */
+ skb_reserve(skb, bp->rx_offset);
+ skb_mark_for_recycle(skb);
+
/* now everything is ready for receiving packet */
- queue->rx_skbuff[entry] = NULL;
+ queue->rx_buff[entry] = NULL;
len = ctrl & bp->rx_frm_len_mask;
netdev_vdbg(bp->dev, "gem_rx %u (len %u)\n", entry, len);
+ dma_sync_single_for_cpu(&bp->pdev->dev,
+ addr, len,
+ page_pool_get_dma_dir(queue->page_pool));
skb_put(skb, len);
- dma_unmap_single(&bp->pdev->dev, addr,
- bp->rx_buffer_size, DMA_FROM_DEVICE);
-
skb->protocol = eth_type_trans(skb, bp->dev);
skb_checksum_none_assert(skb);
if (bp->dev->features & NETIF_F_RXCSUM &&
@@ -1431,7 +1455,7 @@ static int gem_rx(struct macb_queue *queue, struct napi_struct *napi,
napi_gro_receive(napi, skb);
}
- gem_rx_refill(queue);
+ gem_rx_refill(queue, true);
return count;
}
@@ -2387,34 +2411,30 @@ static void macb_init_rx_buffer_size(struct macb *bp, size_t size)
static void gem_free_rx_buffers(struct macb *bp)
{
- struct sk_buff *skb;
- struct macb_dma_desc *desc;
struct macb_queue *queue;
- dma_addr_t addr;
unsigned int q;
+ void *data;
int i;
for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
- if (!queue->rx_skbuff)
+ if (!queue->rx_buff)
continue;
for (i = 0; i < bp->rx_ring_size; i++) {
- skb = queue->rx_skbuff[i];
-
- if (!skb)
+ data = queue->rx_buff[i];
+ if (!data)
continue;
- desc = macb_rx_desc(queue, i);
- addr = macb_get_addr(bp, desc);
-
- dma_unmap_single(&bp->pdev->dev, addr, bp->rx_buffer_size,
- DMA_FROM_DEVICE);
- dev_kfree_skb_any(skb);
- skb = NULL;
+ page_pool_put_full_page(queue->page_pool,
+ virt_to_head_page(data),
+ false);
+ queue->rx_buff[i] = NULL;
}
- kfree(queue->rx_skbuff);
- queue->rx_skbuff = NULL;
+ kfree(queue->rx_buff);
+ queue->rx_buff = NULL;
+ page_pool_destroy(queue->page_pool);
+ queue->page_pool = NULL;
}
}
@@ -2477,13 +2497,13 @@ static int gem_alloc_rx_buffers(struct macb *bp)
for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
size = bp->rx_ring_size * sizeof(struct sk_buff *);
- queue->rx_skbuff = kzalloc(size, GFP_KERNEL);
- if (!queue->rx_skbuff)
+ queue->rx_buff = kzalloc(size, GFP_KERNEL);
+ if (!queue->rx_buff)
return -ENOMEM;
else
netdev_dbg(bp->dev,
- "Allocated %d RX struct sk_buff entries at %p\n",
- bp->rx_ring_size, queue->rx_skbuff);
+ "Allocated %d RX buff entries at %p\n",
+ bp->rx_ring_size, queue->rx_buff);
}
return 0;
}
@@ -2567,6 +2587,32 @@ static int macb_alloc_consistent(struct macb *bp)
return -ENOMEM;
}
+static void gem_create_page_pool(struct macb_queue *queue)
+{
+ unsigned int num_pages = DIV_ROUND_UP(queue->bp->rx_buffer_size, PAGE_SIZE);
+ struct macb *bp = queue->bp;
+ struct page_pool_params pp_params = {
+ .order = order_base_2(num_pages),
+ .flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
+ .pool_size = queue->bp->rx_ring_size,
+ .nid = NUMA_NO_NODE,
+ .dma_dir = DMA_FROM_DEVICE,
+ .dev = &queue->bp->pdev->dev,
+ .napi = &queue->napi_rx,
+ .offset = bp->rx_offset,
+ .max_len = MACB_PP_MAX_BUF_SIZE(num_pages),
+ };
+ struct page_pool *pool;
+
+ pool = page_pool_create(&pp_params);
+ if (IS_ERR(pool)) {
+ netdev_err(queue->bp->dev, "cannot create rx page pool\n");
+ pool = NULL;
+ }
+
+ queue->page_pool = pool;
+}
+
static void macb_init_tieoff(struct macb *bp)
{
struct macb_dma_desc *desc = bp->rx_ring_tieoff;
@@ -2600,7 +2646,8 @@ static void gem_init_rings(struct macb *bp)
queue->rx_tail = 0;
queue->rx_prepared_head = 0;
- gem_rx_refill(queue);
+ gem_create_page_pool(queue);
+ gem_rx_refill(queue, false);
}
macb_init_tieoff(bp);
@@ -5604,6 +5651,12 @@ static int macb_probe(struct platform_device *pdev)
if (err)
goto err_out_phy_exit;
+ if (macb_is_gem(bp)) {
+ bp->rx_offset = MACB_PP_HEADROOM;
+ if (!(bp->caps & MACB_CAPS_RSC))
+ bp->rx_offset += NET_IP_ALIGN;
+ }
+
netif_carrier_off(dev);
err = register_netdev(dev);
--
2.51.1
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