netdev - Re: [PATCH net-next 8/8] net: mscc: PTP Hardware Clock (PHC) support

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Date:   Fri, 5 Jul 2019 09:47:36 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     davem@...emloft.net, alexandre.belloni@...tlin.com,
        UNGLinuxDriver@...rochip.com, ralf@...ux-mips.org,
        paul.burton@...s.com, jhogan@...nel.org, netdev@...r.kernel.org,
        linux-mips@...r.kernel.org, thomas.petazzoni@...tlin.com,
        allan.nielsen@...rochip.com
Subject: Re: [PATCH net-next 8/8] net: mscc: PTP Hardware Clock (PHC) support

On Mon, Jul 01, 2019 at 12:03:27PM +0200, Antoine Tenart wrote:

> +void ocelot_get_hwtimestamp(struct ocelot *ocelot, struct timespec64 *ts)
> +{
> +	/* Read current PTP time to get seconds */
> +	u32 val = ocelot_read_rix(ocelot, PTP_PIN_CFG, TOD_ACC_PIN);

This register is protected by ocelot->ptp_clock_lock from other code
paths, but not in this one!

> +	val &= ~(PTP_PIN_CFG_SYNC | PTP_PIN_CFG_ACTION_MASK | PTP_PIN_CFG_DOM);
> +	val |= PTP_PIN_CFG_ACTION(PTP_PIN_ACTION_SAVE);
> +	ocelot_write_rix(ocelot, val, PTP_PIN_CFG, TOD_ACC_PIN);
> +	ts->tv_sec = ocelot_read_rix(ocelot, PTP_PIN_TOD_SEC_LSB, TOD_ACC_PIN);
	...
> +}


> +static int ocelot_init_timestamp(struct ocelot *ocelot)
> +{
> +	ocelot->ptp_info = ocelot_ptp_clock_info;
> +
> +	ocelot->ptp_clock = ptp_clock_register(&ocelot->ptp_info, ocelot->dev);
> +	if (IS_ERR(ocelot->ptp_clock))
> +		return PTR_ERR(ocelot->ptp_clock);

You need to handle the NULL case:

ptp_clock_register() - register a PTP hardware clock driver

@info:   Structure describing the new clock.
@parent: Pointer to the parent device of the new clock.

Returns a valid pointer on success or PTR_ERR on failure.  If PHC
support is missing at the configuration level, this function
returns NULL, and drivers are expected to gracefully handle that
case separately.

> +
> +	ocelot_write(ocelot, SYS_PTP_CFG_PTP_STAMP_WID(30), SYS_PTP_CFG);
> +	ocelot_write(ocelot, 0xffffffff, ANA_TABLES_PTP_ID_LOW);
> +	ocelot_write(ocelot, 0xffffffff, ANA_TABLES_PTP_ID_HIGH);
> +
> +	ocelot_write(ocelot, PTP_CFG_MISC_PTP_EN, PTP_CFG_MISC);
> +
> +	return 0;
> +}

Thanks,
Richard