Re: [PATCH net] net: airoha: Add dma_rmb() and READ_ONCE() in airoha_qdma_rx_process()

Lorenzo Bianconi
2026-04-03T13:41:11Z

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> Add missing dma_rmb() in airoha_qdma_rx_process routine to make sure the
> DMA read operations are completed when the NIC reports the processing on
> the current descriptor is done. Moreover, add missing READ_ONCE() in
> airoha_qdma_rx_process() for DMA descriptor control fields in order to
> avoid any compiler reordering.
>
> Fixes: 23020f0493270 ("net: airoha: Introduce ethernet support for EN7581 SoC")
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
> drivers/net/ethernet/airoha/airoha_eth.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)

Please drop this version, I will post v2 to add a missing READ_ONCE() for
airoha_qdma_get_gdm_port().

Regards,
Lorenzo

>
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index 95ba99b89428e4cafb91ff7813e43ffeb38e6d9b..29dea8b35f64bfdcf88bc09fd711e0d8b4f7b6fa 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> @@ -612,15 +612,17 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
> while (done < budget) {
> struct airoha_queue_entry *e = &q->entry[q->tail];
> struct airoha_qdma_desc *desc = &q->desc[q->tail];
> - u32 hash, reason, msg1 = le32_to_cpu(desc->msg1);
> - struct page *page = virt_to_head_page(e->buf);
> - u32 desc_ctrl = le32_to_cpu(desc->ctrl);
> + u32 hash, reason, msg1, desc_ctrl;
> struct airoha_gdm_port *port;
> int data_len, len, p;
> + struct page *page;
>
> + desc_ctrl = le32_to_cpu(READ_ONCE(desc->ctrl));
> if (!(desc_ctrl & QDMA_DESC_DONE_MASK))
> break;
>
> + dma_rmb();
> +
> q->tail = (q->tail + 1) % q->ndesc;
> q->queued--;
>
> @@ -637,6 +639,7 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
> if (p < 0 || !eth->ports[p])
> goto free_frag;
>
> + page = virt_to_head_page(e->buf);
> port = eth->ports[p];
> if (!q->skb) { /* first buffer */
> q->skb = napi_build_skb(e->buf, q->buf_size);
> @@ -670,8 +673,8 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
> * DMA descriptor. Report DSA tag to the DSA stack
> * via skb dst info.
> */
> - u32 sptag = FIELD_GET(QDMA_ETH_RXMSG_SPTAG,
> - le32_to_cpu(desc->msg0));
> + u32 msg0 = le32_to_cpu(READ_ONCE(desc->msg0));
> + u32 sptag = FIELD_GET(QDMA_ETH_RXMSG_SPTAG, msg0);
>
> if (sptag < ARRAY_SIZE(port->dsa_meta) &&
> port->dsa_meta[sptag])
> @@ -679,6 +682,7 @@ static int airoha_qdma_rx_process(struct airoha_queue *q, int budget)
> &port->dsa_meta[sptag]->dst);
> }
>
> + msg1 = le32_to_cpu(READ_ONCE(desc->msg1));
> hash = FIELD_GET(AIROHA_RXD4_FOE_ENTRY, msg1);
> if (hash != AIROHA_RXD4_FOE_ENTRY)
> skb_set_hash(q->skb, jhash_1word(hash, 0),
>
> ---
> base-commit: ec7067e661193403a7a00980bda8612db5954142
> change-id: 20260402-airoha_qdma_rx_process-fix-reordering-722308255b65
>
> Best regards,
> --
> Lorenzo Bianconi <lorenzo@kernel.org>
>

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