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

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Date:   Tue, 24 Mar 2020 10:24:36 +0100
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     Vladimir Oltean <olteanv@...il.com>
CC:     Yangbo Lu <yangbo.lu@....com>, 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 Vladimir,

The 03/20/2020 15:20, Vladimir Oltean wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> 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.

It looks like there is no support for absolute start time. But you
should be able to control the phase using the register
PIN_WF_LOW_PERIOD.

> 
> 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

-- 
/Horatiu