netdev - Re: [PATCH net-next v2 4/6] net: mvpp2: ptp: add TAI support

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Date:   Sun, 6 Sep 2020 21:04:02 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Richard Cochran <richardcochran@...il.com>
Cc:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        Matteo Croce <mcroce@...hat.com>,
        Andre Przywara <andre.przywara@....com>,
        Sven Auhagen <sven.auhagen@...eatech.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 4/6] net: mvpp2: ptp: add TAI support

On Sat, Sep 05, 2020 at 10:02:58AM -0700, Richard Cochran wrote:
> On Fri, Sep 04, 2020 at 08:29:27AM +0100, Russell King wrote:
> > Add support for the TAI block in the mvpp2.2 hardware.
> > 
> > Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
> 
> Acked-by: Richard Cochran <richardcochran@...il.com>
> 
> A few minor questions/comments follow...
> 
> > diff --git a/drivers/net/ethernet/marvell/Kconfig b/drivers/net/ethernet/marvell/Kconfig
> > index ef4f35ba077d..a599e44a36a8 100644
> > --- a/drivers/net/ethernet/marvell/Kconfig
> > +++ b/drivers/net/ethernet/marvell/Kconfig
> > @@ -92,6 +92,12 @@ config MVPP2
> >  	  This driver supports the network interface units in the
> >  	  Marvell ARMADA 375, 7K and 8K SoCs.
> >  
> > +config MVPP2_PTP
> > +	bool "Marvell Armada 8K Enable PTP support"
> > +	depends on NETWORK_PHY_TIMESTAMPING
> > +	depends on (PTP_1588_CLOCK = y && MVPP2 = y) || \
> > +		   (PTP_1588_CLOCK && MVPP2 = m)
> 
> So I guess this incantation obviates the need for checking whether
> ptp_clock_register() returns null?

There's no point offering the option if the result isn't going to be
functional.

> > +static long mvpp22_tai_aux_work(struct ptp_clock_info *ptp)
> > +{
> > +	return 0;
> > +}
> 
> Since this is a noop, you can leave 
> 	tai->caps.do_aux_work = mvpp22_tai_aux_work;
> as null.

Ok.

> > +static void mvpp22_tai_set_step(struct mvpp2_tai *tai)
> > +{
> > +	void __iomem *base = tai->base;
> > +	u32 nano, frac;
> > +
> > +	nano = upper_32_bits(tai->period);
> > +	frac = lower_32_bits(tai->period);
> > +
> > +	/* As the fractional nanosecond is a signed offset, if the MSB (sign)
> > +	 * bit is set, we have to increment the whole nanoseconds.
> > +	 */
> > +	if (frac >= 0x80000000)
> > +		nano += 1;
> > +
> > +	mvpp2_tai_write(nano, base + MVPP22_TAI_TOD_STEP_NANO_CR);
> > +	mvpp2_tai_write(frac >> 16, base + MVPP22_TAI_TOD_STEP_FRAC_HIGH);
> > +	mvpp2_tai_write(frac, base + MVPP22_TAI_TOD_STEP_FRAC_LOW);
> > +}
> > +
> > +static void mvpp22_tai_set_tod(struct mvpp2_tai *tai)
> > +{
> > +	struct timespec64 now;
> > +
> > +	ktime_get_real_ts64(&now);
> > +	mvpp22_tai_settime64(&tai->caps, &now);
> > +}
> > +
> > +static void mvpp22_tai_init(struct mvpp2_tai *tai)
> > +{
> > +	void __iomem *base = tai->base;
> > +
> > +	mvpp22_tai_set_step(tai);
> > +
> > +	/* Release the TAI reset */
> > +	mvpp2_tai_modify(base + MVPP22_TAI_CR0, CR0_SW_NRESET, CR0_SW_NRESET);
> > +
> > +	mvpp22_tai_set_tod(tai);
> 
> The consensus on the list seems to be that new PHCs should start
> ticking from time zero (1970), although some older drivers do use
> ktime.  For new clocks, I'd prefer using zero.

Ok.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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