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

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Message-ID: <20200324130733.GA18149@localhost>
Date:   Tue, 24 Mar 2020 06:07:33 -0700
From:   Richard Cochran <richardcochran@...il.com>
To:     Yangbo Lu <yangbo.lu@....com>
Cc:     linux-kernel@...r.kernel.org, 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 Fri, Mar 20, 2020 at 06:37:26PM +0800, Yangbo Lu wrote:
> +static int ocelot_ptp_enable(struct ptp_clock_info *ptp,
> +			     struct ptp_clock_request *rq, int on)
> +{
> +	struct ocelot *ocelot = container_of(ptp, struct ocelot, ptp_info);
> +	enum ocelot_ptp_pins ptp_pin;
> +	struct timespec64 ts;
> +	unsigned long flags;
> +	int pin = -1;
> +	u32 val;
> +	s64 ns;
> +
> +	switch (rq->type) {
> +	case PTP_CLK_REQ_PEROUT:
> +		/* Reject requests with unsupported flags */
> +		if (rq->perout.flags)
> +			return -EOPNOTSUPP;
> +
> +		/*
> +		 * 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.

What dead lock?

When enable(PTP_CLK_REQ_PEROUT, on=0) is called, you don't need to
call ptp_disable_pinfunc().  Just stop the periodic waveform
generator.  The assignment of function to pin remains unchanged.

> +		 */
> +		if (!on)
> +			break;
> +
> +		pin = ptp_find_pin(ocelot->ptp_clock, PTP_PF_PEROUT,
> +				   rq->perout.index);
> +		if (pin == 0)
> +			ptp_pin = PTP_PIN_0;
> +		else if (pin == 1)
> +			ptp_pin = PTP_PIN_1;
> +		else if (pin == 2)
> +			ptp_pin = PTP_PIN_2;
> +		else if (pin == 3)
> +			ptp_pin = PTP_PIN_3;
> +		else
> +			return -EINVAL;

Return -EBUSY here instead.

Thanks,
Richard