linux-kernel - Re: [PATCH 2/4] watchdog: jz4740: Avoid starting watchdog in set

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Message-ID: <20190528192702.GB24853@roeck-us.net>
Date:   Tue, 28 May 2019 12:27:02 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>, od@...c.me,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] watchdog: jz4740: Avoid starting watchdog in
 set_timeout

On Tue, May 21, 2019 at 05:53:11PM +0200, Paul Cercueil wrote:
> Previously the jz4740_wdt_set_timeout() function was starting the timer
> unconditionally, even if it was stopped when that function was entered.
> 
> Now, the timer will be restarted only if it was already running before
> this function is called.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>

Comment inline, but not worth a respin (and I don't have a good idea how to
improve it).

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>  drivers/watchdog/jz4740_wdt.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/jz4740_wdt.c b/drivers/watchdog/jz4740_wdt.c
> index 51be321c775a..f970a7a53084 100644
> --- a/drivers/watchdog/jz4740_wdt.c
> +++ b/drivers/watchdog/jz4740_wdt.c
> @@ -77,6 +77,7 @@ static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  	unsigned int rtc_clk_rate;
>  	unsigned int timeout_value;
>  	unsigned short clock_div = JZ_WDT_CLOCK_DIV_1;
> +	u8 tcer;
>  
>  	rtc_clk_rate = clk_get_rate(drvdata->rtc_clk);
>  
> @@ -92,6 +93,7 @@ static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  		clock_div += (1 << TCU_TCSR_PRESCALE_LSB);
>  	}
>  
> +	tcer = readb(drvdata->base + TCU_REG_WDT_TCER);
>  	writeb(0x0, drvdata->base + TCU_REG_WDT_TCER);
>  	writew(clock_div, drvdata->base + TCU_REG_WDT_TCSR);
>  
> @@ -99,7 +101,7 @@ static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  	writew(0x0, drvdata->base + TCU_REG_WDT_TCNT);
>  	writew(clock_div | JZ_WDT_CLOCK_RTC, drvdata->base + TCU_REG_WDT_TCSR);
>  
> -	writeb(0x1, drvdata->base + TCU_REG_WDT_TCER);
> +	writeb(tcer & TCU_WDT_TCER_TCEN, drvdata->base + TCU_REG_WDT_TCER);

This unnecessarily writes 0 if the timer is not running.

>  
>  	wdt_dev->timeout = new_timeout;
>  	return 0;
> @@ -107,8 +109,11 @@ static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  
>  static int jz4740_wdt_start(struct watchdog_device *wdt_dev)
>  {
> +	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> +
>  	jz4740_timer_enable_watchdog();
>  	jz4740_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
> +	writeb(TCU_WDT_TCER_TCEN, drvdata->base + TCU_REG_WDT_TCER);

This unnecessarily enables the timer even if it is already enabled (that should not
happen, but does if the watchdog is already running at boot).

>  
>  	return 0;
>  }
> -- 
> 2.21.0.593.g511ec345e18
>