linux-kernel - Re: [PATCH net-next v8 06/11] net: ti: prueth: Adds HW timestamping support for PTP using PRU-ICSS IEP module

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Message-ID: <909024001.1496409.1749819222224.JavaMail.zimbra@couthit.local>
Date: Fri, 13 Jun 2025 18:23:42 +0530 (IST)
From: Parvathi Pudi <parvathi@...thit.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Cc: parvathi <parvathi@...thit.com>, danishanwar <danishanwar@...com>, 
	rogerq <rogerq@...nel.org>, andrew+netdev <andrew+netdev@...n.ch>, 
	davem <davem@...emloft.net>, edumazet <edumazet@...gle.com>, 
	kuba <kuba@...nel.org>, pabeni <pabeni@...hat.com>, 
	robh <robh@...nel.org>, krzk+dt <krzk+dt@...nel.org>, 
	conor+dt <conor+dt@...nel.org>, ssantosh <ssantosh@...nel.org>, 
	richardcochran <richardcochran@...il.com>, 
	s hauer <s.hauer@...gutronix.de>, m-karicheri2 <m-karicheri2@...com>, 
	glaroque <glaroque@...libre.com>, afd <afd@...com>, 
	saikrishnag@...vell.com, m-malladi <m-malladi@...com>, 
	jacob e keller <jacob.e.keller@...el.com>, 
	diogo ivo <diogo.ivo@...mens.com>, 
	javier carrasco cruz <javier.carrasco.cruz@...il.com>, 
	horms <horms@...nel.org>, s-anna <s-anna@...com>, 
	basharath <basharath@...thit.com>, 
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>, 
	netdev <netdev@...r.kernel.org>, 
	devicetree <devicetree@...r.kernel.org>, 
	linux-kernel <linux-kernel@...r.kernel.org>, 
	pratheesh <pratheesh@...com>, Prajith Jayarajan <prajith@...com>, 
	Vignesh Raghavendra <vigneshr@...com>, praneeth <praneeth@...com>, 
	srk <srk@...com>, rogerq <rogerq@...com>, 
	krishna <krishna@...thit.com>, pmohan <pmohan@...thit.com>, 
	mohan <mohan@...thit.com>
Subject: Re: [PATCH net-next v8 06/11] net: ti: prueth: Adds HW timestamping
 support for PTP using PRU-ICSS IEP module

Hi,

> On 10/06/2025 13:32, Parvathi Pudi wrote:
>> From: Roger Quadros <rogerq@...com>
>> 
>> PRU-ICSS IEP module, which is capable of timestamping RX and
>> TX packets at HW level, is used for time synchronization by PTP4L.
>> 
>> This change includes interaction between firmware and user space
>> application (ptp4l) with required packet timestamps. The driver
>> initializes the PRU firmware with appropriate mode and configuration
>> flags. Firmware updates local registers with the flags set by driver
>> and uses for further operation. RX SOF timestamp comes along with
>> packet and firmware will rise interrupt with TX SOF timestamp after
>> pushing the packet on to the wire.
>> 
>> IEP driver is available in upstream and we are reusing for hardware
>> configuration for ICSSM as well. On top of that we have extended it
>> with the changes for AM57xx SoC.
>> 
>> Extended ethtool for reading HW timestamping capability of the PRU
>> interfaces.
>> 
>> Currently ordinary clock (OC) configuration has been validated with
>> Linux ptp4l.
>> 
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> Signed-off-by: Andrew F. Davis <afd@...com>
>> Signed-off-by: Basharath Hussain Khaja <basharath@...thit.com>
>> Signed-off-by: Parvathi Pudi <parvathi@...thit.com>
>> ---
>>   drivers/net/ethernet/ti/icssg/icss_iep.c      |  42 ++
>>   drivers/net/ethernet/ti/icssm/icssm_ethtool.c |  23 +
>>   drivers/net/ethernet/ti/icssm/icssm_prueth.c  | 443 +++++++++++++++++-
>>   drivers/net/ethernet/ti/icssm/icssm_prueth.h  |  11 +
>>   .../net/ethernet/ti/icssm/icssm_prueth_ptp.h  |  85 ++++
>>   5 files changed, 602 insertions(+), 2 deletions(-)
>>   create mode 100644 drivers/net/ethernet/ti/icssm/icssm_prueth_ptp.h
> 
> [...]
> 
>> @@ -732,9 +949,22 @@ int icssm_emac_rx_packet(struct prueth_emac *emac, u16
>> *bd_rd_ptr,
>>   		src_addr += actual_pkt_len;
>>   	}
>>   
>> +	if (pkt_info->timestamp) {
>> +		src_addr = (void *)PTR_ALIGN((uintptr_t)src_addr,
>> +					   ICSS_BLOCK_SIZE);
>> +		dst_addr = &ts;
>> +		memcpy(dst_addr, src_addr, sizeof(ts));
>> +	}
>> +
>>   	if (!pkt_info->sv_frame) {
>>   		skb_put(skb, actual_pkt_len);
>>   
>> +		if (icssm_prueth_ptp_rx_ts_is_enabled(emac) &&
>> +		    pkt_info->timestamp) {
>> +			ssh = skb_hwtstamps(skb);
>> +			memset(ssh, 0, sizeof(*ssh));
>> +			ssh->hwtstamp = ns_to_ktime(ts);
>> +		}
>>   		/* send packet up the stack */
>>   		skb->protocol = eth_type_trans(skb, ndev);
>>   		netif_receive_skb(skb);
> 
> Could you please explain why do you need to copy timestamp to a
> temporary variable if you won't use it in some cases? I believe these
> 2 blocks should be placed under the last if condition and simplified a
> bit, like
> 
> +		if (icssm_prueth_ptp_rx_ts_is_enabled(emac) &&
> +		    pkt_info->timestamp) {
> +			src_addr = (void*)PTR_ALIGN((uintptr_t)src_addr,
> +					   ICSS_BLOCK_SIZE);
> +			memcpy(&ts, src_addr, sizeof(ts));
> +			ssh = skb_hwtstamps(skb);
> +			ssh->hwtstamp = ns_to_ktime(ts);
> +		}
> 
> This will avoid useless copy when the packet will be dropped anyway, WDYT?

Yes, we can merge both the if conditions to make it simple.

We will address this in the next version.

Thanks and Regards,
Parvathi.