linux-kernel - Re: [PATCH 3/7] clocksource/cadence_ttc: Store timer frequency in driver data

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Date:	Tue, 12 Nov 2013 17:26:34 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Soren Brinkmann <soren.brinkmann@...inx.com>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Russell King <linux@....linux.org.uk>,
	Michal Simek <michal.simek@...inx.com>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH 3/7] clocksource/cadence_ttc: Store timer frequency in
 driver data

On 11/08/2013 10:21 PM, Soren Brinkmann wrote:
> It is not allowed to call clk_get_rate() from interrupt context. To
> avoid such calls the timer input frequency is stored in the driver's
> data struct which makes it accessible to the driver in any context.
>
> Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
> ---

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>

>   drivers/clocksource/cadence_ttc_timer.c | 21 +++++++++++++--------
>   1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/clocksource/cadence_ttc_timer.c b/drivers/clocksource/cadence_ttc_timer.c
> index b2bb3a4bc205..a92350b55d32 100644
> --- a/drivers/clocksource/cadence_ttc_timer.c
> +++ b/drivers/clocksource/cadence_ttc_timer.c
> @@ -67,11 +67,13 @@
>    * struct ttc_timer - This definition defines local timer structure
>    *
>    * @base_addr:	Base address of timer
> + * @freq:	Timer input clock frequency
>    * @clk:	Associated clock source
>    * @clk_rate_change_nb	Notifier block for clock rate changes
>    */
>   struct ttc_timer {
>   	void __iomem *base_addr;
> +	unsigned long freq;
>   	struct clk *clk;
>   	struct notifier_block clk_rate_change_nb;
>   };
> @@ -196,9 +198,8 @@ static void ttc_set_mode(enum clock_event_mode mode,
>
>   	switch (mode) {
>   	case CLOCK_EVT_MODE_PERIODIC:
> -		ttc_set_interval(timer,
> -				DIV_ROUND_CLOSEST(clk_get_rate(ttce->ttc.clk),
> -					PRESCALE * HZ));
> +		ttc_set_interval(timer, DIV_ROUND_CLOSEST(ttce->ttc.freq,
> +						PRESCALE * HZ));
>   		break;
>   	case CLOCK_EVT_MODE_ONESHOT:
>   	case CLOCK_EVT_MODE_UNUSED:
> @@ -273,6 +274,8 @@ static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base)
>   		return;
>   	}
>
> +	ttccs->ttc.freq = clk_get_rate(ttccs->ttc.clk);
> +
>   	ttccs->ttc.clk_rate_change_nb.notifier_call =
>   		ttc_rate_change_clocksource_cb;
>   	ttccs->ttc.clk_rate_change_nb.next = NULL;
> @@ -298,16 +301,14 @@ static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base)
>   	__raw_writel(CNT_CNTRL_RESET,
>   		     ttccs->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
>
> -	err = clocksource_register_hz(&ttccs->cs,
> -			clk_get_rate(ttccs->ttc.clk) / PRESCALE);
> +	err = clocksource_register_hz(&ttccs->cs, ttccs->ttc.freq / PRESCALE);
>   	if (WARN_ON(err)) {
>   		kfree(ttccs);
>   		return;
>   	}
>
>   	ttc_sched_clock_val_reg = base + TTC_COUNT_VAL_OFFSET;
> -	setup_sched_clock(ttc_sched_clock_read, 16,
> -			clk_get_rate(ttccs->ttc.clk) / PRESCALE);
> +	setup_sched_clock(ttc_sched_clock_read, 16, ttccs->ttc.freq / PRESCALE);
>   }
>
>   static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
> @@ -334,6 +335,9 @@ static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
>   				ndata->new_rate / PRESCALE);
>   		local_irq_restore(flags);
>
> +		/* update cached frequency */
> +		ttc->freq = ndata->new_rate;
> +
>   		/* fall through */
>   	}
>   	case PRE_RATE_CHANGE:
> @@ -367,6 +371,7 @@ static void __init ttc_setup_clockevent(struct clk *clk,
>   	if (clk_notifier_register(ttcce->ttc.clk,
>   				&ttcce->ttc.clk_rate_change_nb))
>   		pr_warn("Unable to register clock notifier.\n");
> +	ttcce->ttc.freq = clk_get_rate(ttcce->ttc.clk);
>
>   	ttcce->ttc.base_addr = base;
>   	ttcce->ce.name = "ttc_clockevent";
> @@ -396,7 +401,7 @@ static void __init ttc_setup_clockevent(struct clk *clk,
>   	}
>
>   	clockevents_config_and_register(&ttcce->ce,
> -			clk_get_rate(ttcce->ttc.clk) / PRESCALE, 1, 0xfffe);
> +			ttcce->ttc.freq / PRESCALE, 1, 0xfffe);
>   }
>
>   /**
>


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