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

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Date:   Tue, 24 Mar 2020 06:19:52 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     "Y.b. Lu" <yangbo.lu@....com>
Cc:     Vladimir Oltean <olteanv@...il.com>,
        lkml <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        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

On Tue, Mar 24, 2020 at 05:21:27AM +0000, Y.b. Lu wrote:
> In my one previous patch, I was suggested to implement PPS with programmable pin periodic clock function.
> But I didn’t find how should PPS be implemented with periodic clock function after checking ptp driver.
> https://patchwork.ozlabs.org/patch/1215464/

Yes, for generating a 1-PPS output waveform, users call ioctl
PTP_CLK_REQ_PEROUT with ptp_perout_request.period={1,0}.

If your device can't control the start time, then it can accept an
unspecified time of ptp_perout_request.start={0,0}.
 
> Vladimir talked with me, for the special PPS case, we may consider,
> if (req.perout.period.sec ==1 && req.perout.period.nsec == 0) and configure WAVEFORM_LOW to be equal to req_perout.start.nsec.
> 
> Richard, do you think is it ok?

Sound okay to me (but I don't know about WAVEFORM_LOW).

> And another problem I am facing is, in .enable() callback (PTP_CLK_REQ_PEROUT request) I defined.
>                 /*
>                  * TODO: support disabling function
>                  * When ptp_disable_pinfunc() is to disable function,
>                  * it has already held pincfg_mux.
>                  * However ptp_find_pin() in .enable() called also needs
>                  * to hold pincfg_mux.
>                  * This causes dead lock. So, just return for function
>                  * disabling, and this needs fix-up.
>                  */
> Hope some suggestions here.

See my reply to the patch.

Thanks,
Richard