linux-kernel - Re: [PATCH 6/6] ptp_ocelot: support 4 programmable pins

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Date:   Fri, 20 Mar 2020 15:20:32 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Yangbo Lu <yangbo.lu@....com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Richard Cochran <richardcochran@...il.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH 6/6] ptp_ocelot: support 4 programmable pins

Hi Yangbo,

On Fri, 20 Mar 2020 at 12:42, Yangbo Lu <yangbo.lu@....com> wrote:
>
> Support 4 programmable pins for only one function periodic
> signal for now. Since the hardware is not able to support
> absolute start time, driver starts periodic signal immediately.
>

Are you absolutely sure it doesn't support absolute start time?
Because that would mean it's pretty useless if the phase of the PTP
clock signal is out of control.

I tested your patch on the LS1028A-RDB board using the following commands:

# Select PEROUT function and assign a channel to each of pins
SWITCH_1588_DAT0 and SWITCH_1588_DAT1
echo '2 0' > /sys/class/ptp/ptp1/pins/switch_1588_dat0
echo '2 1' > /sys/class/ptp/ptp1/pins/switch_1588_dat1
# Generate pulses with 1 second period on channel 0
echo '0 0 0 1 0' > /sys/class/ptp/ptp1/period
# Generate pulses with 1 second period on channel 1
echo '1 0 0 1 0' > /sys/class/ptp/ptp1/period

And here is what I get:
https://drive.google.com/open?id=1ErWufJL0TWv6hKDQdF1pRL5gn4hn4X-r

So the periodic output really starts 'now' just like the print says,
so the output from DAT0 is not even in sync with DAT1.

> Signed-off-by: Yangbo Lu <yangbo.lu@....com>
> ---

Thanks,
-Vladimir