linux-kernel - Re: [PATCH net-next 2/2] net: ethernet: ti: am65-cpsw: Enable RX HW timestamp only for PTP packets

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Date: Mon, 26 Feb 2024 14:18:22 +0200
From: Roger Quadros <rogerq@...nel.org>
To: Siddharth Vadapalli <s-vadapalli@...com>
Cc: Chintan Vankar <c-vankar@...com>, Dan Carpenter
 <dan.carpenter@...aro.org>, Richard Cochran <richardcochran@...il.com>,
 Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
 Eric Dumazet <edumazet@...gle.com>, "David S. Miller" <davem@...emloft.net>,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 Pekka Varis <p-varis@...com>
Subject: Re: [PATCH net-next 2/2] net: ethernet: ti: am65-cpsw: Enable RX HW
 timestamp only for PTP packets

On 24/02/2024 10:59, Siddharth Vadapalli wrote:
> On Mon, Feb 19, 2024 at 12:59:55PM +0200, Roger Quadros wrote:
>> Hi,
>>
>> On 15/02/2024 13:09, Chintan Vankar wrote:
>>> The CPSW peripherals on J7AHP, J7VCL, J7AEP, J7ES, AM64 SoCs have
>>> an errata i2401 "CPSW: Host Timestamps Cause CPSW Port to Lock up".
>>
> ...
> 
>>>  
>>> @@ -856,6 +852,9 @@ static int am65_cpsw_nuss_rx_packets(struct am65_cpsw_common *common,
>>>  		ndev_priv = netdev_priv(ndev);
>>>  		am65_cpsw_nuss_set_offload_fwd_mark(skb, ndev_priv->offload_fwd_mark);
>>>  		skb_put(skb, pkt_len);
>>> +		skb_reset_mac_header(skb);
>>
>> Why do you need to add skb_reset_mac_header here?
>>
>>> +		if (port->rx_ts_enabled)
>>> +			am65_cpts_rx_timestamp(common->cpts, skb);
>>
>> The timestamp should be added before you do skb_put().
> 
> Roger,
> 
> Could you please clarify why the timestamp should be added before
> skb_put()?

My bad. hwtimestamps lies after skb->end so it doesn't matter.

-- 
cheers,
-roger