Subject: Re: [PATCH v4 iwl-next 08/10] idpf: add Tx timestamp flows

From: Simon Horman <[email-masked]>
Date: Tue, 14 Jan 2025 16:26:48 +0000

On Tue, Jan 14, 2025 at 01:11:13PM +0100, Milena Olech wrote:
> Add functions to request Tx timestamp for the PTP packets, read the Tx
> timestamp when the completion tag for that packet is being received,
> extend the Tx timestamp value and set the supported timestamping modes.
> 
> Tx timestamp is requested for the PTP packets by setting a TSYN bit and
> index value in the Tx context descriptor. The driver assumption is that
> the Tx timestamp value is ready to be read when the completion tag is
> received. Then the driver schedules delayed work and the Tx timestamp
> value read is requested through virtchnl message. At the end, the Tx
> timestamp value is extended to 64-bit and provided back to the skb.
> 
> Co-developed-by: Josh Hay <[email-masked]>
> Signed-off-by: Josh Hay <[email-masked]>
> Signed-off-by: Milena Olech <[email-masked]>

...

> diff --git a/drivers/net/ethernet/intel/idpf/idpf_ptp.c b/drivers/net/ethernet/intel/idpf/idpf_ptp.c

...

> +/**
> + * idpf_ptp_request_ts - Request an available Tx timestamp index
> + * @tx_q: Transmit queue on which the Tx timestamp is requested
> + * @skb: The SKB to associate with this timestamp request
> + * @idx: Index of the Tx timestamp latch
> + *
> + * Request tx timestamp index negotiated during PTP init that will be set into
> + * Tx descriptor.
> + *
> + * Return: 0 and the index that can be provided to Tx descriptor on success,
> + * -errno otherwise.
> + */
> +int idpf_ptp_request_ts(struct idpf_tx_queue *tx_q, struct sk_buff *skb,
> +			u32 *idx)
> +{
> +	struct idpf_ptp_tx_tstamp *ptp_tx_tstamp;
> +	struct list_head *head;
> +
> +	/* Get the index from the free latches list */
> +	spin_lock_bh(&tx_q->cached_tstamp_caps->lock_free);
> +
> +	head = &tx_q->cached_tstamp_caps->latches_free;
> +	if (list_empty(head)) {
> +		spin_unlock_bh(&tx_q->cached_tstamp_caps->lock_in_use);

Hi Milena and Josh,

Should the line above be:

		spin_unlock_bh(&tx_q->cached_tstamp_caps->lock_free);
		                                          ^^^^^^^^^

Flagged by Smatch.

> +		return -ENOBUFS;
> +	}
> +
> +	ptp_tx_tstamp = list_first_entry(head, struct idpf_ptp_tx_tstamp,
> +					 list_member);
> +	list_del(&ptp_tx_tstamp->list_member);
> +	spin_unlock_bh(&tx_q->cached_tstamp_caps->lock_free);
> +
> +	ptp_tx_tstamp->skb = skb_get(skb);
> +	skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
> +
> +	/* Move the element to the used latches list */
> +	spin_lock_bh(&tx_q->cached_tstamp_caps->lock_in_use);
> +	list_add(&ptp_tx_tstamp->list_member,
> +		 &tx_q->cached_tstamp_caps->latches_in_use);
> +	spin_unlock_bh(&tx_q->cached_tstamp_caps->lock_in_use);
> +
> +	*idx = ptp_tx_tstamp->idx;
> +
> +	return 0;
> +}

...