Re: [PATCH net-next v5 1/2] net: ethernet: ti: am65-cpts: Enable RX HW timestamp for PTP packets using CPTS FIFO

[Chintan Vankar]

On 04/04/24 16:10, Paolo Abeni wrote:
> On Tue, 2024-04-02 at 17:14 +0530, Chintan Vankar wrote:
> > Add a new function "am65_cpts_rx_timestamp()" which checks for PTP
> > packets from header and timestamps them.
> >
> > Add another function "am65_cpts_find_rx_ts()" which finds CPTS FIFO
> > Event to get the timestamp of received PTP packet.
> >
> > Signed-off-by: Chintan Vankar <c-vankar@xxxxxx>
> > ---
> >
> > Link to v4:
> > https://lore.kernel.org/r/20240327054234.1906957-1-c-vankar@xxxxxx/
> >
> > Changes from v4 to v5:
> > - Updated commit message.
> > - Replaced "list_del_entry()" and "list_add()" functions with equivalent
> >    "list_move()" function.
> >
> >   drivers/net/ethernet/ti/am65-cpts.c | 64 +++++++++++++++++++++++++++++
> >   drivers/net/ethernet/ti/am65-cpts.h |  6 +++
> >   2 files changed, 70 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/ti/am65-cpts.c b/drivers/net/ethernet/ti/am65-cpts.c
> > index c66618d91c28..bc0bfda1db12 100644
> > --- a/drivers/net/ethernet/ti/am65-cpts.c
> > +++ b/drivers/net/ethernet/ti/am65-cpts.c
> > @@ -906,6 +906,70 @@ static int am65_skb_get_mtype_seqid(struct sk_buff *skb, u32 *mtype_seqid)
> >   	return 1;
> >   }
> >   
> > +static u64 am65_cpts_find_rx_ts(struct am65_cpts *cpts, u32 skb_mtype_seqid)
> > +{
> > +	struct list_head *this, *next;
> > +	struct am65_cpts_event *event;
> > +	unsigned long flags;
> > +	u32 mtype_seqid;
> > +	u64 ns = 0;
> > +
> > +	am65_cpts_fifo_read(cpts);
> > +	spin_lock_irqsave(&cpts->lock, flags);
>
> am65_cpts_fifo_read() acquires and releases this same lock. If moving
> to a lockless schema is too complex, you should at least try to acquire
> the lock only once. e.g. factor out a lockless  __am65_cpts_fifo_read
> variant and explicitly acquire the lock before invoke it.

Moving to a lockless schema is complex for now, but I will make the
changes suggested by you in next version.

> > +	list_for_each_safe(this, next, &cpts->events) {
> > +		event = list_entry(this, struct am65_cpts_event, list);
> > +		if (time_after(jiffies, event->tmo)) {
> > +			list_del_init(&event->list);
> > +			list_add(&event->list, &cpts->pool);
>
> Jakub suggested to use list_move() in v4, you should apply that here,
> too.
Okay. I will update that too.

> Cheers,
>
> Paolo