netdev - Re: [PATCH net-next v3 1/4] net: macb: queue tie-off or disable during WOL suspend

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Message-ID: <8829c75f-eea5-41e2-b594-5c648216756a@amd.com>
Date: Fri, 7 Jun 2024 11:24:09 +0530
From: Vineeth Karumanchi <vineeth.karumanchi@....com>
To: Andrew Lunn <andrew@...n.ch>
Cc: nicolas.ferre@...rochip.com, claudiu.beznea@...on.dev,
 davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
 conor+dt@...nel.org, linux@...linux.org.uk, vadim.fedorenko@...ux.dev,
 netdev@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, git@....com
Subject: Re: [PATCH net-next v3 1/4] net: macb: queue tie-off or disable
 during WOL suspend

Hi Andrew,


On 06/06/24 7:14 am, Andrew Lunn wrote:
>> @@ -5224,17 +5257,38 @@ static int __maybe_unused macb_suspend(struct device *dev)
>>   
>>   	if (bp->wol & MACB_WOL_ENABLED) {
>>   		spin_lock_irqsave(&bp->lock, flags);
>> -		/* Flush all status bits */
>> -		macb_writel(bp, TSR, -1);
>> -		macb_writel(bp, RSR, -1);
>> +
>> +		/* Disable Tx and Rx engines before  disabling the queues,
>> +		 * this is mandatory as per the IP spec sheet
>> +		 */
>> +		tmp = macb_readl(bp, NCR);
>> +		macb_writel(bp, NCR, tmp & ~(MACB_BIT(TE) | MACB_BIT(RE)));
> 
> Is there any need to wait for this to complete? What if there is a DMA
> transaction in flight?
> 
> 	Andrew


For newer (r1p10 +) versions , there is a new bit in status register to 
get the active axi transaction, we can leverage it.


For older versions, there is no mechanism to check the current ongoing
transaction, it is a corner case. Currently, in macb_close(), iflink 
down and in suspend we are disabling / cutting clocks to the engine
without checking any DMA transaction in flight.


Thanks
Vineeth