Subject: Re: [PATCH net-next v2 2/2] net: phy: Add Marvell PHY PTP support

From: Simon Horman <[email-masked]>
Date: Tue, 8 Apr 2025 16:49:34 +0100

On Mon, Apr 07, 2025 at 04:03:01PM +0200, Kory Maincent wrote:
> From: Russell King <[email-masked]>
> 
> From: Russell King <[email-masked]>
> 
> Add PTP basic support for Marvell 88E151x PHYs. These PHYs support
> timestamping the egress and ingress of packets, but does not support
> any packet modification.
> 
> The PHYs support hardware pins for providing an external clock for the
> TAI counter, and a separate pin that can be used for event capture or
> generation of a trigger (either a pulse or periodic).  This code does
> not support either of these modes.
> 
> The driver takes inspiration from the Marvell 88E6xxx DSA and DP83640
> drivers.  The hardware is very similar to the implementation found in
> the 88E6xxx DSA driver, but the access methods are very different,
> although it may be possible to create a library that both can use
> along with accessor functions.
> 
> Signed-off-by: Russell King <[email-masked]>
> 
> Add support for interruption.
> Fix L2 PTP encapsulation frame detection.
> Fix first PTP timestamp being dropped.
> Fix Kconfig to depends on MARVELL_PHY.
> Update comments to use kdoc.
> 
> Co-developed-by: Kory Maincent <[email-masked]>
> Signed-off-by: Kory Maincent <[email-masked]>

Hi Kory,

Some minor feedback from my side.

> ---
> 
> Russell I don't know which email I should use, so I keep your old SOB.

Russell's SOB seems to be missing.

...

> diff --git a/drivers/net/phy/marvell/marvell_tai.c b/drivers/net/phy/marvell/marvell_tai.c

...

> +/* Read the global time registers using the readplus command */
> +static u64 marvell_tai_clock_read(const struct cyclecounter *cc)
> +{
> +	struct marvell_tai *tai = cc_to_tai(cc);
> +	struct phy_device *phydev = tai->phydev;
> +	int err, oldpage, lo, hi;
> +
> +	oldpage = phy_select_page(phydev, MARVELL_PAGE_PTP_GLOBAL);
> +	if (oldpage >= 0) {
> +		/* 88e151x says to write 0x8e0e */
> +		ptp_read_system_prets(tai->sts);
> +		err = __phy_write(phydev, PTPG_READPLUS_COMMAND, 0x8e0e);
> +		ptp_read_system_postts(tai->sts);
> +		lo = __phy_read(phydev, PTPG_READPLUS_DATA);
> +		hi = __phy_read(phydev, PTPG_READPLUS_DATA);
> +	}

If the condition above is not met then err, lo, and hi may be used
uninitialised below.

Flagged by W=1 builds with clang 20.1.2, and Smatch.

> +	err = phy_restore_page(phydev, oldpage, err);
> +
> +	if (err || lo < 0 || hi < 0)
> +		return 0;
> +
> +	return lo | hi << 16;
> +}

...

> +int marvell_tai_get(struct marvell_tai **taip, struct phy_device *phydev)
> +{
> +	struct marvell_tai *tai;
> +	unsigned long overflow_ms;
> +	int err;
> +
> +	err = marvell_tai_global_config(phydev);
> +	if (err < 0)
> +		return err;
> +
> +	tai = kzalloc(sizeof(*tai), GFP_KERNEL);
> +	if (!tai)
> +		return -ENOMEM;
> +
> +	mutex_init(&tai->mutex);
> +
> +	tai->phydev = phydev;
> +
> +	/* This assumes a 125MHz clock */
> +	tai->cc_mult = 8 << 28;
> +	tai->cc_mult_num = 1 << 9;
> +	tai->cc_mult_den = 15625U;
> +
> +	tai->cyclecounter.read = marvell_tai_clock_read;
> +	tai->cyclecounter.mask = CYCLECOUNTER_MASK(32);
> +	tai->cyclecounter.mult = tai->cc_mult;
> +	tai->cyclecounter.shift = 28;
> +
> +	overflow_ms = (1ULL << 32 * tai->cc_mult * 1000) >>
> +			tai->cyclecounter.shift;
> +	tai->half_overflow_period = msecs_to_jiffies(overflow_ms / 2);
> +
> +	timecounter_init(&tai->timecounter, &tai->cyclecounter,
> +			 ktime_to_ns(ktime_get_real()));
> +
> +	tai->caps.owner = THIS_MODULE;
> +	snprintf(tai->caps.name, sizeof(tai->caps.name), "Marvell PHY");
> +	/* max_adj of 1000000 is what MV88E6xxx DSA uses */
> +	tai->caps.max_adj = 1000000;
> +	tai->caps.adjfine = marvell_tai_adjfine;
> +	tai->caps.adjtime = marvell_tai_adjtime;
> +	tai->caps.gettimex64 = marvell_tai_gettimex64;
> +	tai->caps.settime64 = marvell_tai_settime64;
> +	tai->caps.do_aux_work = marvell_tai_aux_work;
> +
> +	tai->ptp_clock = ptp_clock_register(&tai->caps, &phydev->mdio.dev);
> +	if (IS_ERR(tai->ptp_clock)) {
> +		kfree(tai);

tai is freed on the line above, but dereferenced on the line below.

Flagged by Smatch.

> +		return PTR_ERR(tai->ptp_clock);
> +	}
> +
> +	ptp_schedule_worker(tai->ptp_clock, tai->half_overflow_period);
> +
> +	spin_lock(&tai_list_lock);
> +	list_add_tail(&tai->tai_node, &tai_list);
> +	spin_unlock(&tai_list_lock);
> +
> +	*taip = tai;
> +
> +	return 0;
> +}

...