linux-kernel - Re: [PATCH 1/3] drivers: clk: st: Support for enable/disable in Clockgen PLLs

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Date:	Wed, 15 Jul 2015 16:48:23 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Gabriel Fernandez <gabriel.fernandez@...aro.org>
Cc:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Maxime Coquelin <maxime.coquelin@...com>,
	Patrice Chotard <patrice.chotard@...com>,
	Russell King <linux@....linux.org.uk>,
	Michael Turquette <mturquette@...libre.com>,
	Peter Griffin <peter.griffin@...aro.org>,
	Pankaj Dev <pankaj.dev@...com>,
	Olivier Bideau <olivier.bideau@...com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Fabian Frederick <fabf@...net.be>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kernel@...inux.com, linux-clk@...r.kernel.org
Subject: Re: [PATCH 1/3] drivers: clk: st: Support for enable/disable in
 Clockgen PLLs

On 07/09, Gabriel Fernandez wrote:
> @@ -270,6 +285,73 @@ static int clkgen_pll_is_enabled(struct clk_hw *hw)
>  	return !poweroff;
>  }
>  
> +static int __clkgen_pll_enable(struct clk_hw *hw)
> +{
> +	struct clkgen_pll *pll = to_clkgen_pll(hw);
> +	unsigned long timeout;
> +	int ret = 0;
> +
> +	if (clkgen_pll_is_enabled(hw))
> +		return 0;
> +
> +	CLKGEN_WRITE(pll, pdn_ctrl, 0);
> +
> +	timeout = jiffies + msecs_to_jiffies(10);

Jiffies isn't guaranteed to increment here because
.enable/.disable is called with irqs disabled and if this is the
only CPU running it won't be getting interrupts to update
jiffies.

> +
> +	while (!clkgen_pll_is_locked(hw)) {
> +		if (time_after(jiffies, timeout))
> +			return -ETIMEDOUT;
> +		cpu_relax();
> +	}
> +
> +	pr_debug("%s:%s enabled\n", __clk_get_name(hw->clk), __func__);
> +
> +	return ret;
> +}

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