linux-kernel - Re: [PATCH net-next v5 1/6] net: ti: icssg-prueth: Add functions to create and destroy Rx/Tx queues

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Message-ID: <3737a9bf-e95b-4ea8-b16b-418b777f407c@ti.com>
Date: Fri, 14 Nov 2025 16:43:21 +0530
From: Meghana Malladi <m-malladi@...com>
To: Simon Horman <horms@...nel.org>
CC: <namcao@...utronix.de>, <vadim.fedorenko@...ux.dev>,
	<jacob.e.keller@...el.com>, <christian.koenig@....com>,
	<sumit.semwal@...aro.org>, <sdf@...ichev.me>, <john.fastabend@...il.com>,
	<hawk@...nel.org>, <daniel@...earbox.net>, <ast@...nel.org>,
	<pabeni@...hat.com>, <kuba@...nel.org>, <edumazet@...gle.com>,
	<davem@...emloft.net>, <andrew+netdev@...n.ch>,
	<linaro-mm-sig@...ts.linaro.org>, <dri-devel@...ts.freedesktop.org>,
	<linux-media@...r.kernel.org>, <bpf@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <srk@...com>, Vignesh Raghavendra
	<vigneshr@...com>, Roger Quadros <rogerq@...nel.org>, <danishanwar@...com>
Subject: Re: [PATCH net-next v5 1/6] net: ti: icssg-prueth: Add functions to
 create and destroy Rx/Tx queues

Hi Simon,

On 11/14/25 16:06, Simon Horman wrote:
> On Tue, Nov 11, 2025 at 03:45:18PM +0530, Meghana Malladi wrote:
> 
> ...
> 
>> diff --git a/drivers/net/ethernet/ti/icssg/icssg_prueth.c b/drivers/net/ethernet/ti/icssg/icssg_prueth.c
>> index 57a7d1ceab08..b66ffbfb499c 100644
>> --- a/drivers/net/ethernet/ti/icssg/icssg_prueth.c
>> +++ b/drivers/net/ethernet/ti/icssg/icssg_prueth.c
>> @@ -735,6 +735,114 @@ static int icssg_update_vlan_mcast(struct net_device *vdev, int vid,
>>   	return 0;
>>   }
>>   
>> +static void prueth_destroy_txq(struct prueth_emac *emac)
>> +{
>> +	int ret, i;
>> +
>> +	atomic_set(&emac->tdown_cnt, emac->tx_ch_num);
>> +	/* ensure new tdown_cnt value is visible */
>> +	smp_mb__after_atomic();
>> +	/* tear down and disable UDMA channels */
>> +	reinit_completion(&emac->tdown_complete);
>> +	for (i = 0; i < emac->tx_ch_num; i++)
>> +		k3_udma_glue_tdown_tx_chn(emac->tx_chns[i].tx_chn, false);
>> +
>> +	ret = wait_for_completion_timeout(&emac->tdown_complete,
>> +					  msecs_to_jiffies(1000));
>> +	if (!ret)
>> +		netdev_err(emac->ndev, "tx teardown timeout\n");
>> +
>> +	for (i = 0; i < emac->tx_ch_num; i++) {
>> +		napi_disable(&emac->tx_chns[i].napi_tx);
>> +		hrtimer_cancel(&emac->tx_chns[i].tx_hrtimer);
>> +		k3_udma_glue_reset_tx_chn(emac->tx_chns[i].tx_chn,
>> +					  &emac->tx_chns[i],
>> +					  prueth_tx_cleanup);
>> +		k3_udma_glue_disable_tx_chn(emac->tx_chns[i].tx_chn);
>> +	}
>> +}
>> +
>> +static void prueth_destroy_rxq(struct prueth_emac *emac)
>> +{
>> +	int i, ret;
>> +
>> +	/* tear down and disable UDMA channels */
>> +	reinit_completion(&emac->tdown_complete);
>> +	k3_udma_glue_tdown_rx_chn(emac->rx_chns.rx_chn, true);
>> +
>> +	/* When RX DMA Channel Teardown is initiated, it will result in an
>> +	 * interrupt and a Teardown Completion Marker (TDCM) is queued into
>> +	 * the RX Completion queue. Acknowledging the interrupt involves
>> +	 * popping the TDCM descriptor from the RX Completion queue via the
>> +	 * RX NAPI Handler. To avoid timing out when waiting for the TDCM to
>> +	 * be popped, schedule the RX NAPI handler to run immediately.
>> +	 */
>> +	if (!napi_if_scheduled_mark_missed(&emac->napi_rx)) {
>> +		if (napi_schedule_prep(&emac->napi_rx))
>> +			__napi_schedule(&emac->napi_rx);
>> +	}
>> +
>> +	ret = wait_for_completion_timeout(&emac->tdown_complete,
>> +					  msecs_to_jiffies(1000));
>> +	if (!ret)
>> +		netdev_err(emac->ndev, "rx teardown timeout\n");
>> +
>> +	for (i = 0; i < PRUETH_MAX_RX_FLOWS; i++) {
>> +		napi_disable(&emac->napi_rx);
>> +		hrtimer_cancel(&emac->rx_hrtimer);
> 
> Hi Meghana,
> 
> Is it intentional that the napi_disable() and hrtimer_cancel()
> are made once for each (possible) flow, rather than just once
> as was the case before this patch?
> 
> Maybe the tx code, which does the same, was used as a template here
> in error?
> 

Currently there is only one flow per Rx channel. But we can enable 
support to add multiple flows to a given given channel. In that case 
napi_disable() and hrtimer_cancel() will be invoked per flow. That being 
said, though right now this for loop is redundant this is a intentional 
change for multiple flows.

> Flagged by Claude Code with https://github.com/masoncl/review-prompts/
> 
>> +		k3_udma_glue_reset_rx_chn(emac->rx_chns.rx_chn, i,
>> +					  &emac->rx_chns,
>> +					  prueth_rx_cleanup);
>> +	}
>> +
>> +	prueth_destroy_xdp_rxqs(emac);
>> +	k3_udma_glue_disable_rx_chn(emac->rx_chns.rx_chn);
>> +}
> 
> ...
> 
>> @@ -905,32 +988,8 @@ static int emac_ndo_stop(struct net_device *ndev)
>>   	else
>>   		__dev_mc_unsync(ndev, icssg_prueth_del_mcast);
>>   
>> -	atomic_set(&emac->tdown_cnt, emac->tx_ch_num);
>> -	/* ensure new tdown_cnt value is visible */
>> -	smp_mb__after_atomic();
>> -	/* tear down and disable UDMA channels */
>> -	reinit_completion(&emac->tdown_complete);
>> -	for (i = 0; i < emac->tx_ch_num; i++)
>> -		k3_udma_glue_tdown_tx_chn(emac->tx_chns[i].tx_chn, false);
>> -
>> -	ret = wait_for_completion_timeout(&emac->tdown_complete,
>> -					  msecs_to_jiffies(1000));
>> -	if (!ret)
>> -		netdev_err(ndev, "tx teardown timeout\n");
>> -
>> -	prueth_reset_tx_chan(emac, emac->tx_ch_num, true);
>> -	for (i = 0; i < emac->tx_ch_num; i++) {
>> -		napi_disable(&emac->tx_chns[i].napi_tx);
>> -		hrtimer_cancel(&emac->tx_chns[i].tx_hrtimer);
>> -	}
>> -
>> -	max_rx_flows = PRUETH_MAX_RX_FLOWS;
>> -	k3_udma_glue_tdown_rx_chn(emac->rx_chns.rx_chn, true);
>> -
>> -	prueth_reset_rx_chan(&emac->rx_chns, max_rx_flows, true);
>> -	prueth_destroy_xdp_rxqs(emac);
>> -	napi_disable(&emac->napi_rx);
>> -	hrtimer_cancel(&emac->rx_hrtimer);
>> +	prueth_destroy_txq(emac);
>> +	prueth_destroy_rxq(emac);
>>   
>>   	cancel_work_sync(&emac->rx_mode_work);
>>   
>> @@ -943,10 +1002,10 @@ static int emac_ndo_stop(struct net_device *ndev)
>>   
>>   	free_irq(emac->tx_ts_irq, emac);
>>   
>> -	free_irq(emac->rx_chns.irq[rx_flow], emac);
>> +	free_irq(emac->rx_chns.irq[PRUETH_RX_FLOW_DATA], emac);
>>   	prueth_ndev_del_tx_napi(emac, emac->tx_ch_num);
>>   
>> -	prueth_cleanup_rx_chns(emac, &emac->rx_chns, max_rx_flows);
>> +	prueth_cleanup_rx_chns(emac, &emac->rx_chns, PRUETH_MAX_RX_FLOWS);
>>   	prueth_cleanup_tx_chns(emac);
>>   
>>   	prueth->emacs_initialized--;
> 
> ...