linux-kernel - Re: [PATCH net-next v7 3/3] net: axienet: Introduce dmaengine support

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Message-ID: <995341e0-d2d7-451e-bd8b-0741cb98bcff@gmail.com>
Date:   Mon, 9 Oct 2023 13:20:36 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Radhey Shyam Pandey <radhey.shyam.pandey@....com>,
        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,
        michal.simek@....com, linux@...linux.org.uk
Cc:     netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        git@....com
Subject: Re: [PATCH net-next v7 3/3] net: axienet: Introduce dmaengine support

On 9/27/23 12:32, Radhey Shyam Pandey wrote:
> Add dmaengine framework to communicate with the xilinx DMAengine
> driver(AXIDMA).
> 
> Axi ethernet driver uses separate channels for transmit and receive.
> Add support for these channels to handle TX and RX with skb and
> appropriate callbacks. Also add axi ethernet core interrupt for
> dmaengine framework support.
> 
> The dmaengine framework was extended for metadata API support.
> However it still needs further enhancements to make it well suited for
> ethernet usecases. The ethernet features i.e ethtool set/get of DMA IP
> properties, ndo_poll_controller,(mentioned in TODO) are not supported
> and it requires follow-up discussions.
> 
> dmaengine support has a dependency on xilinx_dma as it uses
> xilinx_vdma_channel_set_config() API to reset the DMA IP
> which internally reset MAC prior to accessing MDIO.
> 
> Benchmark with netperf:
> 
> xilinx-zcu102-20232:~$ netperf -H 192.168.10.20 -t TCP_STREAM
> MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET
> to 192.168.10.20 () port 0 AF_INET
> Recv   Send    Send
> Socket Socket  Message  Elapsed
> Size   Size    Size     Time     Throughput
> bytes  bytes   bytes    secs.    10^6bits/sec
> 
> 131072  16384  16384    10.03     915.55
> 
> xilinx-zcu102-20232:~$ netperf -H 192.168.10.20 -t UDP_STREAM
> MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET
> to 192.168.10.20 () port 0 AF_INET
> Socket  Message  Elapsed      Messages
> Size    Size     Time         Okay Errors   Throughput
> bytes   bytes    secs            #      #   10^6bits/sec
> 
> 212992   65507   10.00       18192      0     953.35
> 212992           10.00       18192            953.35
> 
> Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@....com>
> ---
[snip]
>   /**
>    * axienet_tx_poll - Invoked once a transmit is completed by the
>    * Axi DMA Tx channel.
> @@ -911,7 +1036,43 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
>   	if (!lp->use_dmaengine)
>   		return axienet_start_xmit_legacy(skb, ndev);
>   	else
> -		return NETDEV_TX_BUSY;
> +		return axienet_start_xmit_dmaengine(skb, ndev);

Did not notice this before, but should consider using a separate set of 
net_device_ops with a different ndo_start_xmit() implementation, rather 
than add another layer of indirection here.
-- 
Florian