Re: [PATCH] rtc: s3c: Rewrite clock handling

[Krzysztof Kozlowski <krzk@kernel.org>]

On Fri, Jan 18, 2019 at 02:27:54PM +0100, Marek Szyprowski wrote:
> s3c_rtc_enable/disable_clk() functions were designed to be called multiple
> times without reference counting, because they were initially used in

s/used/used only/
(if I understand correctly the logic)

> alarm setting/clearing functions, which can be called both when alarm is
> already set or not. Later however, calls to those functions have been added to
> other places in the driver - like time and /proc reading callbacks, what
> results in broken alarm if any of such events happens after the alarm has
> been set. Fix this by simplifying s3c_rtc_enable/disable_clk() functions
> to rely on proper reference counting in clock core and move alarm enable
> counter to s3c_rtc_setaie() function.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/rtc/rtc-s3c.c | 67 ++++++++++++++++++-------------------------
>  1 file changed, 28 insertions(+), 39 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-s3c.c b/drivers/rtc/rtc-s3c.c
> index 04c68178c42d..e682977b4f6e 100644
> --- a/drivers/rtc/rtc-s3c.c
> +++ b/drivers/rtc/rtc-s3c.c
> @@ -39,7 +39,7 @@ struct s3c_rtc {
>  	void __iomem *base;
>  	struct clk *rtc_clk;
>  	struct clk *rtc_src_clk;
> -	bool clk_disabled;
> +	bool alarm_enabled;
>  
>  	const struct s3c_rtc_data *data;
>  
> @@ -47,7 +47,7 @@ struct s3c_rtc {
>  	int irq_tick;
>  
>  	spinlock_t pie_lock;
> -	spinlock_t alarm_clk_lock;
> +	spinlock_t alarm_lock;

Maybe add short comment that it protects only "alarm_enabled" property?

>  
>  	int ticnt_save;
>  	int ticnt_en_save;
> @@ -70,44 +70,28 @@ struct s3c_rtc_data {
>  
>  static int s3c_rtc_enable_clk(struct s3c_rtc *info)
>  {
> -	unsigned long irq_flags;
>  	int ret = 0;
>  
> -	spin_lock_irqsave(&info->alarm_clk_lock, irq_flags);
> +	ret = clk_enable(info->rtc_clk);
> +	if (ret)
> +		goto out;

The out label is now empty so just "return ret". It is easier to read -
no need to jump anywhere to see the simple return.

>  
> -	if (info->clk_disabled) {
> -		ret = clk_enable(info->rtc_clk);
> -		if (ret)
> +	if (info->data->needs_src_clk) {
> +		ret = clk_enable(info->rtc_src_clk);
> +		if (ret) {
> +			clk_disable(info->rtc_clk);
>  			goto out;
> -
> -		if (info->data->needs_src_clk) {
> -			ret = clk_enable(info->rtc_src_clk);
> -			if (ret) {
> -				clk_disable(info->rtc_clk);
> -				goto out;
> -			}
>  		}
> -		info->clk_disabled = false;
>  	}
> -
>  out:
> -	spin_unlock_irqrestore(&info->alarm_clk_lock, irq_flags);
> -
>  	return ret;
>  }
>  
>  static void s3c_rtc_disable_clk(struct s3c_rtc *info)
>  {
> -	unsigned long irq_flags;
> -
> -	spin_lock_irqsave(&info->alarm_clk_lock, irq_flags);
> -	if (!info->clk_disabled) {
> -		if (info->data->needs_src_clk)
> -			clk_disable(info->rtc_src_clk);
> -		clk_disable(info->rtc_clk);
> -		info->clk_disabled = true;
> -	}
> -	spin_unlock_irqrestore(&info->alarm_clk_lock, irq_flags);
> +	if (info->data->needs_src_clk)
> +		clk_disable(info->rtc_src_clk);
> +	clk_disable(info->rtc_clk);
>  }
>  
>  /* IRQ Handlers */
> @@ -135,6 +119,7 @@ static irqreturn_t s3c_rtc_alarmirq(int irq, void *id)
>  static int s3c_rtc_setaie(struct device *dev, unsigned int enabled)
>  {
>  	struct s3c_rtc *info = dev_get_drvdata(dev);
> +	unsigned long flags;
>  	unsigned int tmp;
>  	int ret;
>  
> @@ -151,17 +136,19 @@ static int s3c_rtc_setaie(struct device *dev, unsigned int enabled)
>  
>  	writeb(tmp, info->base + S3C2410_RTCALM);
>  
> -	s3c_rtc_disable_clk(info);
> +	spin_lock_irqsave(&info->alarm_lock, flags);
>  
> -	if (enabled) {
> -		ret = s3c_rtc_enable_clk(info);
> -		if (ret)
> -			return ret;
> -	} else {
> +	if (info->alarm_enabled && !enabled)
>  		s3c_rtc_disable_clk(info);
> -	}
> +	else if (!info->alarm_enabled && enabled)
> +		ret = s3c_rtc_enable_clk(info);
>  
> -	return 0;
> +	info->alarm_enabled = enabled;
> +	spin_unlock_irqrestore(&info->alarm_lock, flags);
> +
> +	s3c_rtc_disable_clk(info);
> +
> +	return ret;
>  }
>  
>  /* Set RTC frequency */
> @@ -357,10 +344,10 @@ static int s3c_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
>  
>  	writeb(alrm_en, info->base + S3C2410_RTCALM);
>  
> -	s3c_rtc_disable_clk(info);
> -
>  	s3c_rtc_setaie(dev, alrm->enabled);
>  
> +	s3c_rtc_disable_clk(info);

I do not understand this change - why do you have to move the disable
clk? The s3c_rtc_setaie() takes care about clock enabling/disabling for
the time of accessing registers.

> +
>  	return 0;
>  }
>  
> @@ -491,7 +478,7 @@ static int s3c_rtc_probe(struct platform_device *pdev)
>  		return -EINVAL;
>  	}
>  	spin_lock_init(&info->pie_lock);
> -	spin_lock_init(&info->alarm_clk_lock);
> +	spin_lock_init(&info->alarm_lock);
>  
>  	platform_set_drvdata(pdev, info);
>  
> @@ -591,6 +578,8 @@ static int s3c_rtc_probe(struct platform_device *pdev)
>  
>  	s3c_rtc_setfreq(info, 1);
>  
> +	s3c_rtc_disable_clk(info);

I cannot find the reason why this is related to this particular change.
I mean, it looks reasonable because previously the clock looked like it
was enabled all the time... but maybe this should be separate pach?


Best regards,
Krzysztof

> +
>  	return 0;
>  
>  err_nortc:
> -- 
> 2.17.1
>