Subject: Re: [PATCH net v2] net: airoha: Add missing bits in airoha_qdma_cleanup_tx_queue()

From: Lorenzo Bianconi <[email-masked]>
Date: Wed, 15 Apr 2026 19:58:50 +0200

> On Tue, Apr 14, 2026 at 08:50:52AM +0200, Lorenzo Bianconi wrote:
> > Similar to airoha_qdma_cleanup_rx_queue(), reset DMA TX descriptors in
> > airoha_qdma_cleanup_tx_queue routine. Moreover, reset TX_DMA_IDX to
> > TX_CPU_IDX to notify the NIC the QDMA TX ring is empty.
> > 
> > Fixes: 23020f0493270 ("net: airoha: Introduce ethernet support for EN7581 SoC")
> > Signed-off-by: Lorenzo Bianconi <[email-masked]>
> > ---
> > Changes in v2:
> > - Move q->ndesc initialization at end of airoha_qdma_init_tx routine in
> >   order to avoid any possible NULL pointer dereference in
> >   airoha_qdma_cleanup_tx_queue()
> 
> This seems to be a separate issue.
> If so, I think it should be split out into a separate patch.

Sorry, I missed this comment.
Ack. I will repost splitting this in two separated patches.

Regards,
Lorenzo

> 
> > - Check if q->tx_list is empty in airoha_qdma_cleanup_tx_queue()
> > - Link to v1: https://lore.kernel.org/r/[email-masked]
> 
> I think it was covered in the review Jakub forwarded for v1.  But FTR,
> Sashiko has some feedback on this patch in the form of an existing bug
> (that should almost certainly be handled separately from this patch).
> 
> > ---
> >  drivers/net/ethernet/airoha/airoha_eth.c | 41 ++++++++++++++++++++++++++------
> >  1 file changed, 34 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> > index 9e995094c32a..3c1a2bc68c42 100644
> > --- a/drivers/net/ethernet/airoha/airoha_eth.c
> > +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> > @@ -966,27 +966,27 @@ static int airoha_qdma_init_tx_queue(struct airoha_queue *q,
> >  	dma_addr_t dma_addr;
> >  
> >  	spin_lock_init(&q->lock);
> > -	q->ndesc = size;
> >  	q->qdma = qdma;
> >  	q->free_thr = 1 + MAX_SKB_FRAGS;
> >  	INIT_LIST_HEAD(&q->tx_list);
> >  
> > -	q->entry = devm_kzalloc(eth->dev, q->ndesc * sizeof(*q->entry),
> > +	q->entry = devm_kzalloc(eth->dev, size * sizeof(*q->entry),
> >  				GFP_KERNEL);
> >  	if (!q->entry)
> >  		return -ENOMEM;
> >  
> > -	q->desc = dmam_alloc_coherent(eth->dev, q->ndesc * sizeof(*q->desc),
> > +	q->desc = dmam_alloc_coherent(eth->dev, size * sizeof(*q->desc),
> >  				      &dma_addr, GFP_KERNEL);
> >  	if (!q->desc)
> >  		return -ENOMEM;
> >  
> > -	for (i = 0; i < q->ndesc; i++) {
> > +	for (i = 0; i < size; i++) {
> >  		u32 val = FIELD_PREP(QDMA_DESC_DONE_MASK, 1);
> >  
> >  		list_add_tail(&q->entry[i].list, &q->tx_list);
> >  		WRITE_ONCE(q->desc[i].ctrl, cpu_to_le32(val));
> >  	}
> > +	q->ndesc = size;
> >  
> >  	/* xmit ring drop default setting */
> >  	airoha_qdma_set(qdma, REG_TX_RING_BLOCKING(qid),
> > @@ -1051,13 +1051,17 @@ static int airoha_qdma_init_tx(struct airoha_qdma *qdma)
> >  
> >  static void airoha_qdma_cleanup_tx_queue(struct airoha_queue *q)
> >  {
> > -	struct airoha_eth *eth = q->qdma->eth;
> > -	int i;
> > +	struct airoha_qdma *qdma = q->qdma;
> > +	struct airoha_eth *eth = qdma->eth;
> > +	int i, qid = q - &qdma->q_tx[0];
> > +	struct airoha_queue_entry *e;
> > +	u16 index = 0;
> >  
> >  	spin_lock_bh(&q->lock);
> >  	for (i = 0; i < q->ndesc; i++) {
> > -		struct airoha_queue_entry *e = &q->entry[i];
> 
> super nit: In v2 e is always used within a block (here and in the hunk below).
>            So I would lean towards declaring e in the blocks where it is
> 	   used.
> 
> 	   No need to repost just for this!
> 
> > +		struct airoha_qdma_desc *desc = &q->desc[i];
> >  
> > +		e = &q->entry[i];
> >  		if (!e->dma_addr)
> >  			continue;
> >  
> > @@ -1067,8 +1071,31 @@ static void airoha_qdma_cleanup_tx_queue(struct airoha_queue *q)
> >  		e->dma_addr = 0;
> >  		e->skb = NULL;
> >  		list_add_tail(&e->list, &q->tx_list);
> > +
> > +		/* Reset DMA descriptor */
> > +		WRITE_ONCE(desc->ctrl, 0);
> > +		WRITE_ONCE(desc->addr, 0);
> > +		WRITE_ONCE(desc->data, 0);
> > +		WRITE_ONCE(desc->msg0, 0);
> > +		WRITE_ONCE(desc->msg1, 0);
> > +		WRITE_ONCE(desc->msg2, 0);
> > +
> >  		q->queued--;
> >  	}
> > +
> > +	if (!list_empty(&q->tx_list)) {
> > +		e = list_first_entry(&q->tx_list, struct airoha_queue_entry,
> > +				     list);
> > +		index = e - q->entry;
> > +	}
> > +	/* Set TX_DMA_IDX to TX_CPU_IDX to notify the hw the QDMA TX ring is
> > +	 * empty.
> > +	 */
> > +	airoha_qdma_rmw(qdma, REG_TX_CPU_IDX(qid), TX_RING_CPU_IDX_MASK,
> > +			FIELD_PREP(TX_RING_CPU_IDX_MASK, index));
> > +	airoha_qdma_rmw(qdma, REG_TX_DMA_IDX(qid), TX_RING_DMA_IDX_MASK,
> > +			FIELD_PREP(TX_RING_DMA_IDX_MASK, index));
> > +
> >  	spin_unlock_bh(&q->lock);
> >  }
> >  
> > 
> > ---
> > base-commit: 2cd7e6971fc2787408ceef17906ea152791448cf
> > change-id: 20260410-airoha_qdma_cleanup_tx_queue-fix-net-93375f5ee80f
> > 
> > Best regards,
> > -- 
> > Lorenzo Bianconi <[email-masked]>
> >