Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20200320103726.32559-1-yangbo.lu@nxp.com> <20200320103726.32559-7-yangbo.lu@nxp.com>
In-Reply-To: <20200320103726.32559-7-yangbo.lu@nxp.com>
From:   Vladimir Oltean <olteanv@gmail.com>
Date:   Fri, 20 Mar 2020 15:20:32 +0200
Message-ID: <CA+h21hoBwDuWCFbO70u1FAERB8zc5F+H5URBkn=2_bpRRRz1oA@mail.gmail.com>
Subject: Re: [PATCH 6/6] ptp_ocelot: support 4 programmable pins
To:     Yangbo Lu <yangbo.lu@nxp.com>
Cc:     lkml <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        "David S . Miller" <davem@davemloft.net>,
        Richard Cochran <richardcochran@gmail.com>,
        Vladimir Oltean <vladimir.oltean@nxp.com>,
        Claudiu Manoil <claudiu.manoil@nxp.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Yangbo,

On Fri, 20 Mar 2020 at 12:42, Yangbo Lu <yangbo.lu@nxp.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@nxp.com>
> ---

Thanks,
-Vladimir