[PATCH net] net: airoha: dma map xmit frags with skb_frag_dma_map()
Harshitha Ramamurthy
hramamurthy at google.com
Thu Jun 25 15:59:10 PDT 2026
On Thu, Jun 25, 2026 at 2:43 AM Lorenzo Bianconi <lorenzo at kernel.org> wrote:
>
> Map xmit skb fragments using skb_frag_dma_map() instead of
> dma_map_single(skb_frag_address()). skb_frag_address() relies on
> page_address() to obtain a kernel virtual address, which is not
> guaranteed to work for all page types (e.g. highmem pages or
> user-pinned pages from MSG_ZEROCOPY).
> skb_frag_dma_map() maps the fragment directly via its struct page and
> offset through dma_map_page(), avoiding the need for a kernel virtual
> address entirely.
> Introduce an enum airoha_dma_map_type to track how each queue entry was
> mapped (single vs page), so that the matching unmap function is called
> on completion and in error paths.
>
> Fixes: 23020f049327 ("net: airoha: Introduce ethernet support for EN7581 SoC")
> Signed-off-by: Lorenzo Bianconi <lorenzo at kernel.org>
Reviewed-by: Harshitha Ramamurthy <hramamurthy at google.com>
> ---
> drivers/net/ethernet/airoha/airoha_eth.c | 61 ++++++++++++++++++++------------
> drivers/net/ethernet/airoha/airoha_eth.h | 7 ++++
> 2 files changed, 45 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index 932b3a3df2e5..1caf6766f2c0 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> @@ -944,6 +944,25 @@ static void airoha_qdma_wake_netdev_txqs(struct airoha_queue *q)
> q->txq_stopped = false;
> }
>
> +static void airoha_unmap_xmit_buf(struct airoha_eth *eth,
> + struct airoha_queue_entry *e)
> +{
> + switch (e->dma_type) {
> + case AIROHA_DMA_MAP_PAGE:
> + dma_unmap_page(eth->dev, e->dma_addr, e->dma_len,
> + DMA_TO_DEVICE);
> + break;
> + case AIROHA_DMA_MAP_SINGLE:
> + dma_unmap_single(eth->dev, e->dma_addr, e->dma_len,
> + DMA_TO_DEVICE);
> + break;
> + case AIROHA_DMA_UNMAPPED:
> + default:
> + break;
> + }
> + e->dma_type = AIROHA_DMA_UNMAPPED;
> +}
> +
> static int airoha_qdma_tx_napi_poll(struct napi_struct *napi, int budget)
> {
> struct airoha_tx_irq_queue *irq_q;
> @@ -1006,9 +1025,7 @@ static int airoha_qdma_tx_napi_poll(struct napi_struct *napi, int budget)
> skb = e->skb;
> e->skb = NULL;
>
> - dma_unmap_single(eth->dev, e->dma_addr, e->dma_len,
> - DMA_TO_DEVICE);
> - e->dma_addr = 0;
> + airoha_unmap_xmit_buf(eth, e);
> list_add_tail(&e->list, &q->tx_list);
>
> WRITE_ONCE(desc->msg0, 0);
> @@ -1177,12 +1194,10 @@ static void airoha_qdma_tx_cleanup(struct airoha_qdma *qdma)
> struct airoha_qdma_desc *desc = &q->desc[j];
> struct sk_buff *skb = e->skb;
>
> - if (!e->dma_addr)
> + if (e->dma_type == AIROHA_DMA_UNMAPPED)
> continue;
>
> - dma_unmap_single(qdma->eth->dev, e->dma_addr,
> - e->dma_len, DMA_TO_DEVICE);
> - e->dma_addr = 0;
> + airoha_unmap_xmit_buf(qdma->eth, e);
> list_add_tail(&e->list, &q->tx_list);
>
> WRITE_ONCE(desc->ctrl, 0);
> @@ -2193,8 +2208,8 @@ static netdev_tx_t airoha_dev_xmit(struct sk_buff *skb,
> struct netdev_queue *txq;
> struct airoha_queue *q;
> LIST_HEAD(tx_list);
> + dma_addr_t addr;
> int i = 0, qid;
> - void *data;
> u16 index;
> u8 fport;
>
> @@ -2250,24 +2265,22 @@ static netdev_tx_t airoha_dev_xmit(struct sk_buff *skb,
> return NETDEV_TX_BUSY;
> }
>
> - len = skb_headlen(skb);
> - data = skb->data;
> -
> e = list_first_entry(&q->tx_list, struct airoha_queue_entry,
> list);
> + len = skb_headlen(skb);
> + addr = dma_map_single(netdev->dev.parent, skb->data, len,
> + DMA_TO_DEVICE);
> + if (unlikely(dma_mapping_error(netdev->dev.parent, addr)))
> + goto error_unlock;
> +
> + e->dma_type = AIROHA_DMA_MAP_SINGLE;
> index = e - q->entry;
>
> while (true) {
> struct airoha_qdma_desc *desc = &q->desc[index];
> skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
> - dma_addr_t addr;
> u32 val;
>
> - addr = dma_map_single(netdev->dev.parent, data, len,
> - DMA_TO_DEVICE);
> - if (unlikely(dma_mapping_error(netdev->dev.parent, addr)))
> - goto error_unmap;
> -
> list_move_tail(&e->list, &tx_list);
> e->skb = i == nr_frags - 1 ? skb : NULL;
> e->dma_addr = addr;
> @@ -2291,8 +2304,13 @@ static netdev_tx_t airoha_dev_xmit(struct sk_buff *skb,
> if (++i == nr_frags)
> break;
>
> - data = skb_frag_address(frag);
> len = skb_frag_size(frag);
> + addr = skb_frag_dma_map(netdev->dev.parent, frag, 0, len,
> + DMA_TO_DEVICE);
> + if (unlikely(dma_mapping_error(netdev->dev.parent, addr)))
> + goto error_unmap;
> +
> + e->dma_type = AIROHA_DMA_MAP_PAGE;
> }
> q->queued += i;
>
> @@ -2313,11 +2331,8 @@ static netdev_tx_t airoha_dev_xmit(struct sk_buff *skb,
> return NETDEV_TX_OK;
>
> error_unmap:
> - list_for_each_entry(e, &tx_list, list) {
> - dma_unmap_single(netdev->dev.parent, e->dma_addr, e->dma_len,
> - DMA_TO_DEVICE);
> - e->dma_addr = 0;
> - }
> + list_for_each_entry(e, &tx_list, list)
> + airoha_unmap_xmit_buf(dev->eth, e);
> list_splice(&tx_list, &q->tx_list);
> error_unlock:
> spin_unlock_bh(&q->lock);
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.h b/drivers/net/ethernet/airoha/airoha_eth.h
> index d7ff8c5200e2..2765244d937c 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.h
> +++ b/drivers/net/ethernet/airoha/airoha_eth.h
> @@ -170,12 +170,19 @@ enum trtcm_param {
> #define TRTCM_TOKEN_RATE_MASK GENMASK(23, 6)
> #define TRTCM_TOKEN_RATE_FRACTION_MASK GENMASK(5, 0)
>
> +enum airoha_dma_map_type {
> + AIROHA_DMA_UNMAPPED,
> + AIROHA_DMA_MAP_SINGLE,
> + AIROHA_DMA_MAP_PAGE,
> +};
> +
> struct airoha_queue_entry {
> union {
> void *buf;
> struct {
> struct list_head list;
> struct sk_buff *skb;
> + enum airoha_dma_map_type dma_type;
> };
> };
> dma_addr_t dma_addr;
>
> ---
> base-commit: 232c4ca2343d1181cbfc061f9856d9591e397579
> change-id: 20260625-airoha-eth-skb_frag_dma_map-bcccd5d6e4b1
>
> Best regards,
> --
> Lorenzo Bianconi <lorenzo at kernel.org>
>
>
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