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Date:   Fri, 10 Aug 2018 06:36:48 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Paul Cercueil <paul@crapouillou.net>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        Paul Burton <paul.burton@mips.com>,
        James Hogan <jhogan@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Lee Jones <lee.jones@linaro.org>,
        Mathieu Malaterre <malat@debian.org>,
        Ezequiel Garcia <ezequiel@collabora.co.uk>,
        linux-pwm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org,
        linux-mips@linux-mips.org, linux-doc@vger.kernel.org,
        linux-clk@vger.kernel.org
Subject: Re: [PATCH v6 08/24] watchdog: jz4740: Use WDT clock provided by TCU
 driver
Message-ID: <20180810133648.GA29028@roeck-us.net>
References: <20180809214414.20905-1-paul@crapouillou.net>
 <20180809214414.20905-9-paul@crapouillou.net>
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On Thu, Aug 09, 2018 at 11:43:58PM +0200, Paul Cercueil wrote:
> Instead of requesting the "ext" clock and handling the watchdog clock
> divider and gating in the watchdog driver, we now request and use the
> "wdt" clock that is supplied by the ingenic-timer "TCU" driver.
> 
> The major benefit is that the watchdog's clock rate and parent can now
> be specified from within devicetree, instead of hardcoded in the driver.
> 
> Also, this driver won't poke anymore into the TCU registers to
> enable/disable the clock, as this is now handled by the TCU driver.
> 
> On the bad side, we break the ABI with devicetree - as we now request a
> different clock. In this very specific case it is still okay, as every
> Ingenic JZ47xx-based board out there compile the devicetree within the
> kernel; so it's still time to push breaking changes, in order to get a
> clean devicetree that won't break once it musn't.
> 
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>

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

> ---
>  drivers/watchdog/Kconfig      |  2 +
>  drivers/watchdog/jz4740_wdt.c | 86 +++++++++++++++++--------------------------
>  2 files changed, 36 insertions(+), 52 deletions(-)
> 
>  v5: New patch
> 
>  v6: - Split regmap change to new patch 09/24
>      - The code now sets the WDT clock to the smallest rate possible and
>        calculates the maximum timeout from that
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 9af07fd92763..834222abbbdb 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1476,7 +1476,9 @@ config INDYDOG
>  config JZ4740_WDT
>  	tristate "Ingenic jz4740 SoC hardware watchdog"
>  	depends on MACH_JZ4740 || MACH_JZ4780
> +	depends on COMMON_CLK
>  	select WATCHDOG_CORE
> +	select INGENIC_TIMER
>  	help
>  	  Hardware driver for the built-in watchdog timer on Ingenic jz4740 SoCs.
>  
> diff --git a/drivers/watchdog/jz4740_wdt.c b/drivers/watchdog/jz4740_wdt.c
> index ec4d99a830ba..1d504ecf45e1 100644
> --- a/drivers/watchdog/jz4740_wdt.c
> +++ b/drivers/watchdog/jz4740_wdt.c
> @@ -26,25 +26,9 @@
>  #include <linux/err.h>
>  #include <linux/of.h>
>  
> -#include <asm/mach-jz4740/timer.h>
> -
>  #define JZ_REG_WDT_TIMER_DATA     0x0
>  #define JZ_REG_WDT_COUNTER_ENABLE 0x4
>  #define JZ_REG_WDT_TIMER_COUNTER  0x8
> -#define JZ_REG_WDT_TIMER_CONTROL  0xC
> -
> -#define JZ_WDT_CLOCK_PCLK 0x1
> -#define JZ_WDT_CLOCK_RTC  0x2
> -#define JZ_WDT_CLOCK_EXT  0x4
> -
> -#define JZ_WDT_CLOCK_DIV_SHIFT   3
> -
> -#define JZ_WDT_CLOCK_DIV_1    (0 << JZ_WDT_CLOCK_DIV_SHIFT)
> -#define JZ_WDT_CLOCK_DIV_4    (1 << JZ_WDT_CLOCK_DIV_SHIFT)
> -#define JZ_WDT_CLOCK_DIV_16   (2 << JZ_WDT_CLOCK_DIV_SHIFT)
> -#define JZ_WDT_CLOCK_DIV_64   (3 << JZ_WDT_CLOCK_DIV_SHIFT)
> -#define JZ_WDT_CLOCK_DIV_256  (4 << JZ_WDT_CLOCK_DIV_SHIFT)
> -#define JZ_WDT_CLOCK_DIV_1024 (5 << JZ_WDT_CLOCK_DIV_SHIFT)
>  
>  #define DEFAULT_HEARTBEAT 5
>  #define MAX_HEARTBEAT     2048
> @@ -65,7 +49,8 @@ MODULE_PARM_DESC(heartbeat,
>  struct jz4740_wdt_drvdata {
>  	struct watchdog_device wdt;
>  	void __iomem *base;
> -	struct clk *rtc_clk;
> +	struct clk *clk;
> +	unsigned long clk_rate;
>  };
>  
>  static int jz4740_wdt_ping(struct watchdog_device *wdt_dev)
> @@ -80,31 +65,12 @@ static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  				    unsigned int new_timeout)
>  {
>  	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> -	unsigned int rtc_clk_rate;
> -	unsigned int timeout_value;
> -	unsigned short clock_div = JZ_WDT_CLOCK_DIV_1;
> -
> -	rtc_clk_rate = clk_get_rate(drvdata->rtc_clk);
> -
> -	timeout_value = rtc_clk_rate * new_timeout;
> -	while (timeout_value > 0xffff) {
> -		if (clock_div == JZ_WDT_CLOCK_DIV_1024) {
> -			/* Requested timeout too high;
> -			* use highest possible value. */
> -			timeout_value = 0xffff;
> -			break;
> -		}
> -		timeout_value >>= 2;
> -		clock_div += (1 << JZ_WDT_CLOCK_DIV_SHIFT);
> -	}
> +	u16 timeout_value = (u16)(drvdata->clk_rate * new_timeout);
>  
>  	writeb(0x0, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
> -	writew(clock_div, drvdata->base + JZ_REG_WDT_TIMER_CONTROL);
>  
>  	writew((u16)timeout_value, drvdata->base + JZ_REG_WDT_TIMER_DATA);
>  	writew(0x0, drvdata->base + JZ_REG_WDT_TIMER_COUNTER);
> -	writew(clock_div | JZ_WDT_CLOCK_RTC,
> -		drvdata->base + JZ_REG_WDT_TIMER_CONTROL);
>  
>  	writeb(0x1, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
>  
> @@ -114,7 +80,13 @@ static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
>  
>  static int jz4740_wdt_start(struct watchdog_device *wdt_dev)
>  {
> -	jz4740_timer_enable_watchdog();
> +	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
> +	int ret;
> +
> +	ret = clk_prepare_enable(drvdata->clk);
> +	if (ret)
> +		return ret;
> +
>  	jz4740_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
>  
>  	return 0;
> @@ -125,7 +97,7 @@ static int jz4740_wdt_stop(struct watchdog_device *wdt_dev)
>  	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
>  
>  	writeb(0x0, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
> -	jz4740_timer_disable_watchdog();
> +	clk_disable_unprepare(drvdata->clk);
>  
>  	return 0;
>  }
> @@ -163,26 +135,42 @@ MODULE_DEVICE_TABLE(of, jz4740_wdt_of_matches);
>  
>  static int jz4740_wdt_probe(struct platform_device *pdev)
>  {
> +	struct device *dev = &pdev->dev;
>  	struct jz4740_wdt_drvdata *drvdata;
>  	struct watchdog_device *jz4740_wdt;
>  	struct resource	*res;
> +	long rate;
>  	int ret;
>  
> -	drvdata = devm_kzalloc(&pdev->dev, sizeof(struct jz4740_wdt_drvdata),
> -			       GFP_KERNEL);
> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
>  	if (!drvdata)
>  		return -ENOMEM;
>  
> -	if (heartbeat < 1 || heartbeat > MAX_HEARTBEAT)
> -		heartbeat = DEFAULT_HEARTBEAT;
> +	drvdata->clk = devm_clk_get(&pdev->dev, "wdt");
> +	if (IS_ERR(drvdata->clk)) {
> +		dev_err(&pdev->dev, "cannot find WDT clock\n");
> +		return PTR_ERR(drvdata->clk);
> +	}
> +
> +	/* Set smallest clock possible */
> +	rate = clk_round_rate(drvdata->clk, 1);
> +	if (rate < 0)
> +		return rate;
>  
> +	ret = clk_set_rate(drvdata->clk, rate);
> +	if (ret)
> +		return ret;
> +
> +	drvdata->clk_rate = rate;
>  	jz4740_wdt = &drvdata->wdt;
>  	jz4740_wdt->info = &jz4740_wdt_info;
>  	jz4740_wdt->ops = &jz4740_wdt_ops;
> -	jz4740_wdt->timeout = heartbeat;
>  	jz4740_wdt->min_timeout = 1;
> -	jz4740_wdt->max_timeout = MAX_HEARTBEAT;
> -	jz4740_wdt->parent = &pdev->dev;
> +	jz4740_wdt->max_timeout = 0xffff / rate;
> +	jz4740_wdt->timeout = clamp(heartbeat,
> +				    jz4740_wdt->min_timeout,
> +				    jz4740_wdt->max_timeout);
> +	jz4740_wdt->parent = dev;
>  	watchdog_set_nowayout(jz4740_wdt, nowayout);
>  	watchdog_set_drvdata(jz4740_wdt, drvdata);
>  
> @@ -191,12 +179,6 @@ static int jz4740_wdt_probe(struct platform_device *pdev)
>  	if (IS_ERR(drvdata->base))
>  		return PTR_ERR(drvdata->base);
>  
> -	drvdata->rtc_clk = devm_clk_get(&pdev->dev, "rtc");
> -	if (IS_ERR(drvdata->rtc_clk)) {
> -		dev_err(&pdev->dev, "cannot find RTC clock\n");
> -		return PTR_ERR(drvdata->rtc_clk);
> -	}
> -
>  	ret = devm_watchdog_register_device(&pdev->dev, &drvdata->wdt);
>  	if (ret < 0)
>  		return ret;
> -- 
> 2.11.0
>