RE: [PATCH net-next v5 2/5] net: phy: microchip_ptp : Add ptp library for Microchip phys

[Divya.Koppera]

Hi Paolo Abeni,

Thanks for the review.

> -----Original Message-----
> From: Paolo Abeni <pabeni@xxxxxxxxxx>
> Sent: Thursday, December 5, 2024 3:17 PM
> To: Divya Koppera - I30481 <Divya.Koppera@xxxxxxxxxxxxx>;
> andrew@xxxxxxx; Arun Ramadoss - I17769
> <Arun.Ramadoss@xxxxxxxxxxxxx>; UNGLinuxDriver
> <UNGLinuxDriver@xxxxxxxxxxxxx>; hkallweit1@xxxxxxxxx;
> linux@xxxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx;
> kuba@xxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> richardcochran@xxxxxxxxx; vadim.fedorenko@xxxxxxxxx
> Subject: Re: [PATCH net-next v5 2/5] net: phy: microchip_ptp : Add ptp library
> for Microchip phys
> 
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> On 12/3/24 09:52, Divya Koppera wrote:
> > +struct mchp_ptp_clock *mchp_ptp_probe(struct phy_device *phydev, u8
> mmd,
> > +                                   u16 clk_base_addr, u16
> > +port_base_addr) {
> > +     struct mchp_ptp_clock *clock;
> > +     int rc;
> > +
> > +     clock = devm_kzalloc(&phydev->mdio.dev, sizeof(*clock), GFP_KERNEL);
> > +     if (!clock)
> > +             return ERR_PTR(-ENOMEM);
> > +
> > +     clock->port_base_addr   = port_base_addr;
> > +     clock->clk_base_addr    = clk_base_addr;
> > +     clock->mmd              = mmd;
> > +
> > +     /* Register PTP clock */
> > +     clock->caps.owner          = THIS_MODULE;
> > +     snprintf(clock->caps.name, 30, "%s", phydev->drv->name);
> > +     clock->caps.max_adj        = MCHP_PTP_MAX_ADJ;
> > +     clock->caps.n_ext_ts       = 0;
> > +     clock->caps.pps            = 0;
> > +     clock->caps.adjfine        = mchp_ptp_ltc_adjfine;
> > +     clock->caps.adjtime        = mchp_ptp_ltc_adjtime;
> > +     clock->caps.gettime64      = mchp_ptp_ltc_gettime64;
> > +     clock->caps.settime64      = mchp_ptp_ltc_settime64;
> > +     clock->ptp_clock = ptp_clock_register(&clock->caps,
> > +                                           &phydev->mdio.dev);
> > +     if (IS_ERR(clock->ptp_clock))
> > +             return ERR_PTR(-EINVAL);
> > +
> > +     /* Initialize the SW */
> > +     skb_queue_head_init(&clock->tx_queue);
> > +     skb_queue_head_init(&clock->rx_queue);
> > +     INIT_LIST_HEAD(&clock->rx_ts_list);
> > +     spin_lock_init(&clock->rx_ts_lock);
> > +     mutex_init(&clock->ptp_lock);
> 
> The s/w initialization is completed after successfully registering the new ptp
> clock, is that safe? It looks like it may race with ptp callbacks.

If I understand your comment correctly ptp_lock in the clock instance is not initialized before registering the clock.
Rest of the initializations are related to packet processing and also depends on phydev->default_timestamp and mii_ts instance only after which packets will be forwarded to phy.
As we are also re-initializing the clock ptp4l/application need to restart.

Initializing ptp_lock before registering the clock should be safe from ptp point of view. 

Let me know your opinion?

> 
> Cheers,
> 
> Paolo

Thanks,
Divya