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Date: Fri, 7 Jun 2024 11:24:09 +0530
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH net-next v3 1/4] net: macb: queue tie-off or disable
 during WOL suspend
Content-Language: en-GB
To: Andrew Lunn <andrew@lunn.ch>
Cc: nicolas.ferre@microchip.com, claudiu.beznea@tuxon.dev,
 davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
 pabeni@redhat.com, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
 conor+dt@kernel.org, linux@armlinux.org.uk, vadim.fedorenko@linux.dev,
 netdev@vger.kernel.org, devicetree@vger.kernel.org,
 linux-kernel@vger.kernel.org, git@amd.com
References: <20240605102457.4050539-1-vineeth.karumanchi@amd.com>
 <20240605102457.4050539-2-vineeth.karumanchi@amd.com>
 <90da3dd6-e361-46d0-b547-c662b649b03d@lunn.ch>
From: Vineeth Karumanchi <vineeth.karumanchi@amd.com>
In-Reply-To: <90da3dd6-e361-46d0-b547-c662b649b03d@lunn.ch>
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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