linux-kernel - Re: [PATCH 2/7] net: stmmac: Balance PTP reference clock enable/disable

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Message-ID: <53f18077-6a4d-339f-192e-287a1f889fb7@kapsi.fi>
Date:   Mon, 27 Feb 2017 11:31:39 +0200
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Thierry Reding <thierry.reding@...il.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Alexandre Courbot <gnurou@...il.com>,
        Jon Hunter <jonathanh@...dia.com>, netdev@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] net: stmmac: Balance PTP reference clock
 enable/disable

On 23.02.2017 19:24, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
>
> clk_prepare_enable() and clk_disable_unprepare() for this clock aren't
> properly balanced, which can trigger a WARN_ON() in the common clock
> framework.
>
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c     | 4 ++++
>  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 1 -
>  2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 3cbe09682afe..6b7a5ce19589 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1711,6 +1711,10 @@ static int stmmac_hw_setup(struct net_device *dev, bool init_ptp)
>  	stmmac_mmc_setup(priv);
>
>  	if (init_ptp) {
> +		ret = clk_prepare_enable(priv->plat->clk_ptp_ref);
> +		if (ret < 0)
> +			netdev_warn(priv->dev, "failed to enable PTP reference clock: %d\n", ret);
> +

Should we return an error code if the clock enable fails?

>  		ret = stmmac_init_ptp(priv);
>  		if (ret == -EOPNOTSUPP)
>  			netdev_warn(priv->dev, "PTP not supported by HW\n");
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index 5b18355c0d2b..d285d6cfbd0d 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -365,7 +365,6 @@ stmmac_probe_config_dt(struct platform_device *pdev, const char **mac)
>  		plat->clk_ptp_ref = NULL;
>  		dev_warn(&pdev->dev, "PTP uses main clock\n");
>  	} else {
> -		clk_prepare_enable(plat->clk_ptp_ref);
>  		plat->clk_ptp_rate = clk_get_rate(plat->clk_ptp_ref);
>  		dev_dbg(&pdev->dev, "PTP rate %d\n", plat->clk_ptp_rate);
>  	}
>

It seems like there will still be a refcount mismatch for the clock if 
any of the request_irqs that are after stmmac_hw_setup in stmmac_open fail.

Cheers,
Mikko.