[PATCH net-next v4 1/2] net: airoha: refactor QDMA start/stop into reusable helpers

[Lorenzo Bianconi]

> Factor out airoha_qdma_start() and airoha_qdma_stop() from
> airoha_dev_open() and airoha_dev_stop(). These helpers will be reused
> by the QDMA hot-migration logic introduced in the next patch to
> dynamically switch GDM3/GDM4 ports between LAN and WAN QDMA blocks.
> Add a DMA engine busy poll in airoha_qdma_stop() to wait for in-flight
> DMA transfers to complete before cleaning up TX queues.
> 
> Tested-by: Madhur Agrawal <madhur.agrawal at airoha.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo at kernel.org>
> ---
>  drivers/net/ethernet/airoha/airoha_eth.c | 53 ++++++++++++++++++++++----------
>  1 file changed, 36 insertions(+), 17 deletions(-)

Both of the issues reportd by sashiko here are not introduced by this patch
https://sashiko.dev/#/patchset/20260610-airoha-ethtool-priv_flags-v4-0-60e89cf28fea%40kernel.org

Regards,
Lorenzo

> 
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index 5a8e84fa9918..aeac66df5f3b 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> @@ -1771,6 +1771,40 @@ static void airoha_update_hw_stats(struct airoha_gdm_dev *dev)
>  	spin_unlock(&port->stats.lock);
>  }
>  
> +static void airoha_qdma_start(struct airoha_qdma *qdma)
> +{
> +	airoha_qdma_set(qdma, REG_QDMA_GLOBAL_CFG,
> +			GLOBAL_CFG_TX_DMA_EN_MASK |
> +			GLOBAL_CFG_RX_DMA_EN_MASK);
> +	atomic_inc(&qdma->users);
> +}
> +
> +static void airoha_qdma_stop(struct airoha_qdma *qdma)
> +{
> +	u32 status;
> +
> +	if (!atomic_dec_and_test(&qdma->users))
> +		return;
> +
> +	airoha_qdma_clear(qdma, REG_QDMA_GLOBAL_CFG,
> +			  GLOBAL_CFG_TX_DMA_EN_MASK |
> +			  GLOBAL_CFG_RX_DMA_EN_MASK);
> +
> +	if (read_poll_timeout(airoha_qdma_rr, status,
> +			      !(status & (GLOBAL_CFG_TX_DMA_BUSY_MASK |
> +					  GLOBAL_CFG_RX_DMA_BUSY_MASK)),
> +			      USEC_PER_MSEC, 50 * USEC_PER_MSEC, true,
> +			      qdma, REG_QDMA_GLOBAL_CFG))
> +		dev_warn(qdma->eth->dev, "QDMA DMA engine busy timeout\n");
> +
> +	for (int i = 0; i < ARRAY_SIZE(qdma->q_tx); i++) {
> +		if (!qdma->q_tx[i].ndesc)
> +			continue;
> +
> +		airoha_qdma_cleanup_tx_queue(&qdma->q_tx[i]);
> +	}
> +}
> +
>  static int airoha_dev_open(struct net_device *netdev)
>  {
>  	int err, len = ETH_HLEN + netdev->mtu + ETH_FCS_LEN;
> @@ -1806,10 +1840,7 @@ static int airoha_dev_open(struct net_device *netdev)
>  	}
>  	port->users++;
>  
> -	airoha_qdma_set(qdma, REG_QDMA_GLOBAL_CFG,
> -			GLOBAL_CFG_TX_DMA_EN_MASK |
> -			GLOBAL_CFG_RX_DMA_EN_MASK);
> -	atomic_inc(&qdma->users);
> +	airoha_qdma_start(qdma);
>  
>  	if (!airoha_is_lan_gdm_dev(dev) &&
>  	    airoha_ppe_is_enabled(qdma->eth, 1))
> @@ -1862,19 +1893,7 @@ static int airoha_dev_stop(struct net_device *netdev)
>  		airoha_set_gdm_port_fwd_cfg(qdma->eth,
>  					    REG_GDM_FWD_CFG(port->id),
>  					    FE_PSE_PORT_DROP);
> -
> -	if (atomic_dec_and_test(&qdma->users)) {
> -		airoha_qdma_clear(qdma, REG_QDMA_GLOBAL_CFG,
> -				  GLOBAL_CFG_TX_DMA_EN_MASK |
> -				  GLOBAL_CFG_RX_DMA_EN_MASK);
> -
> -		for (i = 0; i < ARRAY_SIZE(qdma->q_tx); i++) {
> -			if (!qdma->q_tx[i].ndesc)
> -				continue;
> -
> -			airoha_qdma_cleanup_tx_queue(&qdma->q_tx[i]);
> -		}
> -	}
> +	airoha_qdma_stop(qdma);
>  
>  	return 0;
>  }
> 
> -- 
> 2.54.0
> 
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