linux-kernel - Re: [PATCH] arm: at91: do not disable/enable clocks in a row

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Date:	Wed, 30 Mar 2016 20:06:52 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm: at91: do not disable/enable clocks in a row

On 03/29/2016 03:26 PM, Sebastian Andrzej Siewior wrote:
> Currently the driver will disable the clock and enable it one line later
> if it is switching from periodic mode into one shot.
> This can be avoided and causes a needless warning on -RT.

I don't see the connection between the description and the content of 
the patch.

It can be avoided by not disabling the clock when going to periodic / 
oneshot.

The function below suggest clk_enable() is called twice, is that the 
real issue ?

> Tested-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> Acked-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>   drivers/clocksource/tcb_clksrc.c | 33 +++++++++++++++++++++++++++++----
>   1 file changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/clocksource/tcb_clksrc.c b/drivers/clocksource/tcb_clksrc.c
> index 4da2af9694a2..ed1ae4445e8d 100644
> --- a/drivers/clocksource/tcb_clksrc.c
> +++ b/drivers/clocksource/tcb_clksrc.c
> @@ -74,6 +74,7 @@ static struct clocksource clksrc = {
>   struct tc_clkevt_device {
>   	struct clock_event_device	clkevt;
>   	struct clk			*clk;
> +	bool				clk_enabled;
>   	void __iomem			*regs;
>   };
>
> @@ -91,6 +92,24 @@ static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
>    */
>   static u32 timer_clock;
>
> +static void tc_clk_disable(struct clock_event_device *d)
> +{
> +	struct tc_clkevt_device *tcd = to_tc_clkevt(d);
> +
> +	clk_disable(tcd->clk);
> +	tcd->clk_enabled = false;
> +}
> +
> +static void tc_clk_enable(struct clock_event_device *d)
> +{
> +	struct tc_clkevt_device *tcd = to_tc_clkevt(d);
> +
> +	if (tcd->clk_enabled)
> +		return;
> +	clk_enable(tcd->clk);
> +	tcd->clk_enabled = true;
> +}

This function.


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