Message-ID: <B256D81BAE5131468A838E5D7A243641C9F820CB@penmbx01>
Date:	Wed, 29 Jul 2015 00:38:27 +0000
From:	"Yang, Wenyou" <Wenyou.Yang@...el.com>
To:	Guenter Roeck <linux@...ck-us.net>,
	"wim@...ana.be" <wim@...ana.be>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>
CC:	"sylvain.rochet@...secur.com" <sylvain.rochet@...secur.com>,
	"Ferre, Nicolas" <Nicolas.FERRE@...el.com>,
	"boris.brezillon@...e-electrons.com" 
	<boris.brezillon@...e-electrons.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH 1/2] drivers: watchdog: at91sam9_wdt: add new feature
 support

Hi Guenter,

Thank you very much for your review.

> -----Original Message-----
> From: Guenter Roeck [mailto:linux@...ck-us.net]
> Sent: 2015年7月28日 15:14
> To: Yang, Wenyou; wim@...ana.be; robh+dt@...nel.org; pawel.moll@....com;
> mark.rutland@....com; ijc+devicetree@...lion.org.uk; galak@...eaurora.org
> Cc: sylvain.rochet@...secur.com; Ferre, Nicolas; boris.brezillon@...e-
> electrons.com; devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
> watchdog@...r.kernel.org; linux-arm-kernel@...ts.infradead.org
> Subject: Re: [PATCH 1/2] drivers: watchdog: at91sam9_wdt: add new feature
> support
> 
> On 07/28/2015 12:00 AM, Wenyou Yang wrote:
> > In the datasheet, the new feature is describled as "WDT_MR can be
> > written until a LOCKMR command is issued in WDT_CR".
> > That is to say, as long as the bootstrap and u-boot don't issue a
> > LOCKMR command, WDT_MR can be written in kernel.
> >
> > So the driver can enable/disable the watchdog timer hardware, set
> > WDV(Watchdog Counter Value) and WDD(Watchdog Delta Value) fields of
> > WDT_MR register to set the watchdog timer timeout.
> >
> > The timer is not necessary that regularly sends a keepalive ping to
> > the watchdog timer hardware.
> >
> > It is introduced from sama5d4 SoCs.
> >
> Since there are so many changes, I wonder is a separate driver would make more
> sense.
Yes, a bit many changes.
I thought reuse the driver code.
If a separate driver, I am afraid it includes much duplicated code. 
After all, it is for the same device with different feature. 

I don't think it is necessary to have multiple drivers for the same peripheral with different feature.
 
> 
> Thoughts ?
> 
> Guenter
> 
> > Signed-off-by: Wenyou Yang <wenyou.yang@...el.com>
> > ---
> >   drivers/watchdog/at91sam9_wdt.c |  255
> ++++++++++++++++++++++++++++-----------
> >   drivers/watchdog/at91sam9_wdt.h |    4 +
> >   2 files changed, 190 insertions(+), 69 deletions(-)
> >
> > diff --git a/drivers/watchdog/at91sam9_wdt.c
> > b/drivers/watchdog/at91sam9_wdt.c index 1443b3c..6b61084 100644
> > --- a/drivers/watchdog/at91sam9_wdt.c
> > +++ b/drivers/watchdog/at91sam9_wdt.c
> > @@ -10,9 +10,12 @@
> >    */
> >
> >   /*
> > + * For AT91SAM9x SoCs, the Watchdog Timer has the following constraint.
> >    * The Watchdog Timer Mode Register can be only written to once. If the
> >    * timeout need to be set from Linux, be sure that the bootstrap or the
> >    * bootloader doesn't write to this register.
> > + * From SAMA5D4, the Watchdog Timer Mode Register can be written
> > + * until a LOCKMR command is issued in WDT_CR.
> >    */
> >
> >   #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt @@ -80,6 +83,11 @@
> > MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started
> "
> >   	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> >
> >   #define to_wdt(wdd) container_of(wdd, struct at91wdt, wdd)
> > +
> > +struct at91wdt_variant {
> > +	bool mr_writable;
> > +};
> > +
> >   struct at91wdt {
> >   	struct watchdog_device wdd;
> >   	void __iomem *base;
> > @@ -90,6 +98,9 @@ struct at91wdt {
> >   	unsigned long heartbeat;	/* WDT heartbeat in jiffies */
> >   	bool nowayout;
> >   	unsigned int irq;
> > +	bool use_timer;
> > +	bool enabled;
> > +	struct at91wdt_variant *drv_data;
> >   };
> >
> >   /*
> > ......................................................................... */ @@ -133,21 +144,67 @@
> static void at91_ping(unsigned long data)
> >   static int at91_wdt_start(struct watchdog_device *wdd)
> >   {
> >   	struct at91wdt *wdt = to_wdt(wdd);
> > -	/* calculate when the next userspace timeout will be */
> > -	wdt->next_heartbeat = jiffies + wdd->timeout * HZ;
> > +	u32 reg;
> > +
> > +	if (wdt->drv_data->mr_writable) {
> > +		reg = wdt_read(wdt, AT91_WDT_MR);
> > +		reg &= ~AT91_WDT_WDDIS;
> > +		wdt_write(wdt, AT91_WDT_MR, reg);
> > +	} else {
> > +		/* calculate when the next userspace timeout will be */
> > +		wdt->next_heartbeat = jiffies + wdd->timeout * HZ;
> > +	}
> > +
> >   	return 0;
> >   }
> >
> >   static int at91_wdt_stop(struct watchdog_device *wdd)
> >   {
> > -	/* The watchdog timer hardware can not be stopped... */
> > +	struct at91wdt *wdt = to_wdt(wdd);
> > +	u32 reg;
> > +
> > +	if (wdt->drv_data->mr_writable) {
> > +		reg = wdt_read(wdt, AT91_WDT_MR);
> > +		reg |= AT91_WDT_WDDIS;
> > +		wdt_write(wdt, AT91_WDT_MR, reg);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int at91_wdt_ping(struct watchdog_device *wdd) {
> > +	struct at91wdt *wdt = to_wdt(wdd);
> > +
> > +	wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY |
> AT91_WDT_WDRSTT);
> > +
> >   	return 0;
> >   }
> >
> >   static int at91_wdt_set_timeout(struct watchdog_device *wdd, unsigned int
> new_timeout)
> >   {
> > -	wdd->timeout = new_timeout;
> > -	return at91_wdt_start(wdd);
> > +	struct at91wdt *wdt = to_wdt(wdd);
> > +	u32 reg, timeout;
> > +
> > +	if (wdt->drv_data->mr_writable) {
> > +		timeout = secs_to_ticks(new_timeout);
> > +		if (timeout > WDT_COUNTER_MAX_TICKS)
> > +			return -EINVAL;
> > +
> > +		reg = wdt_read(wdt, AT91_WDT_MR);
> > +		reg &= ~AT91_WDT_WDV;
> > +		reg |= AT91_WDT_WDV_(timeout);
> > +		reg &= ~AT91_WDT_WDD;
> > +		reg |= AT91_WDT_WDD_(timeout);
> > +		wdt_write(wdt, AT91_WDT_MR, reg);
> > +
> > +		wdd->timeout = new_timeout;
> > +
> > +		return 0;
> > +	} else {
> > +		wdd->timeout = new_timeout;
> > +		return at91_wdt_start(wdd);
> > +	}
> >   }
> >
> >   static int at91_wdt_init(struct platform_device *pdev, struct
> > at91wdt *wdt) @@ -161,50 +218,65 @@ static int at91_wdt_init(struct
> platform_device *pdev, struct at91wdt *wdt)
> >   	unsigned long max_heartbeat;
> >   	struct device *dev = &pdev->dev;
> >
> > -	tmp = wdt_read(wdt, AT91_WDT_MR);
> > -	if ((tmp & mask) != (wdt->mr & mask)) {
> > -		if (tmp == WDT_MR_RESET) {
> > -			wdt_write(wdt, AT91_WDT_MR, wdt->mr);
> > -			tmp = wdt_read(wdt, AT91_WDT_MR);
> > +	if (wdt->drv_data->mr_writable) {
> > +		wdt->use_timer = false;
> > +
> > +		wdt_write(wdt, AT91_WDT_MR, wdt->mr | AT91_WDT_WDDIS);
> > +	} else {
> > +		wdt->use_timer = true;
> > +
> > +		tmp = wdt_read(wdt, AT91_WDT_MR);
> > +		if ((tmp & mask) != (wdt->mr & mask)) {
> > +			if (tmp == WDT_MR_RESET) {
> > +				wdt_write(wdt, AT91_WDT_MR, wdt->mr);
> > +				tmp = wdt_read(wdt, AT91_WDT_MR);
> > +			}
> >   		}
> > -	}
> >
> > -	if (tmp & AT91_WDT_WDDIS) {
> > -		if (wdt->mr & AT91_WDT_WDDIS)
> > -			return 0;
> > -		dev_err(dev, "watchdog is disabled\n");
> > -		return -EINVAL;
> > +		if (tmp & AT91_WDT_WDDIS) {
> > +			if (wdt->mr & AT91_WDT_WDDIS)
> > +				return 0;
> > +
> > +			dev_err(dev, "watchdog is disabled\n");
> > +			return -EINVAL;
> > +		}
> >   	}
> >
> > -	value = tmp & AT91_WDT_WDV;
> > -	delta = (tmp & AT91_WDT_WDD) >> 16;
> > +	tmp = wdt_read(wdt, AT91_WDT_MR);
> > +	wdt->enabled = (tmp & AT91_WDT_WDDIS) ? false : true;
> >
> > -	if (delta < value)
> > -		min_heartbeat = ticks_to_hz_roundup(value - delta);
> > +	if (wdt->use_timer) {
> > +		value = tmp & AT91_WDT_WDV;
> > +		delta = (tmp & AT91_WDT_WDD) >> 16;
> >
> > -	max_heartbeat = ticks_to_hz_rounddown(value);
> > -	if (!max_heartbeat) {
> > -		dev_err(dev,
> > -			"heartbeat is too small for the system to handle it
> correctly\n");
> > -		return -EINVAL;
> > -	}
> > +		if (delta < value)
> > +			min_heartbeat = ticks_to_hz_roundup(value - delta);
> >
> > -	/*
> > -	 * Try to reset the watchdog counter 4 or 2 times more often than
> > -	 * actually requested, to avoid spurious watchdog reset.
> > -	 * If this is not possible because of the min_heartbeat value, reset
> > -	 * it at the min_heartbeat period.
> > -	 */
> > -	if ((max_heartbeat / 4) >= min_heartbeat)
> > -		wdt->heartbeat = max_heartbeat / 4;
> > -	else if ((max_heartbeat / 2) >= min_heartbeat)
> > -		wdt->heartbeat = max_heartbeat / 2;
> > -	else
> > -		wdt->heartbeat = min_heartbeat;
> > -
> > -	if (max_heartbeat < min_heartbeat + 4)
> > -		dev_warn(dev,
> > -			 "min heartbeat and max heartbeat might be too close for
> the system to handle it correctly\n");
> > +		max_heartbeat = ticks_to_hz_rounddown(value);
> > +		if (!max_heartbeat) {
> > +			dev_err(dev,
> > +				"heartbeat is too small for the system to handle it
> correctly\n");
> > +			return -EINVAL;
> > +		}
> > +
> > +		/*
> > +		 * Try to reset the watchdog counter 4 or 2 times more often than
> > +		 * actually requested, to avoid spurious watchdog reset.
> > +		 * If this is not possible because of the min_heartbeat value, reset
> > +		 * it at the min_heartbeat period.
> > +		 */
> > +		if ((max_heartbeat / 4) >= min_heartbeat)
> > +			wdt->heartbeat = max_heartbeat / 4;
> > +		else if ((max_heartbeat / 2) >= min_heartbeat)
> > +			wdt->heartbeat = max_heartbeat / 2;
> > +		else
> > +			wdt->heartbeat = min_heartbeat;
> > +
> > +		if (max_heartbeat < min_heartbeat + 4) {
> > +			dev_warn(dev,
> > +				 "min heartbeat and max heartbeat might be too
> close for the system to handle it correctly\n");
> > +		}
> > +	}
> >
> >   	if ((tmp & AT91_WDT_WDFIEN) && wdt->irq) {
> >   		err = request_irq(wdt->irq, wdt_interrupt, @@ -215,21 +287,24
> @@
> > static int at91_wdt_init(struct platform_device *pdev, struct at91wdt *wdt)
> >   			return err;
> >   	}
> >
> > -	if ((tmp & wdt->mr_mask) != (wdt->mr & wdt->mr_mask))
> > -		dev_warn(dev,
> > -			 "watchdog already configured differently (mr = %x
> expecting %x)\n",
> > -			 tmp & wdt->mr_mask, wdt->mr & wdt->mr_mask);
> > +	if (wdt->use_timer) {
> > +		if ((tmp & wdt->mr_mask) != (wdt->mr & wdt->mr_mask)) {
> > +			dev_warn(dev,
> > +				 "watchdog already configured differently (mr
> = %x expecting %x)\n",
> > +				 tmp & wdt->mr_mask, wdt->mr & wdt->mr_mask);
> > +		}
> >
> > -	setup_timer(&wdt->timer, at91_ping, (unsigned long)wdt);
> > +		setup_timer(&wdt->timer, at91_ping, (unsigned long)wdt);
> >
> > -	/*
> > -	 * Use min_heartbeat the first time to avoid spurious watchdog reset:
> > -	 * we don't know for how long the watchdog counter is running, and
> > -	 *  - resetting it right now might trigger a watchdog fault reset
> > -	 *  - waiting for heartbeat time might lead to a watchdog timeout
> > -	 *    reset
> > -	 */
> > -	mod_timer(&wdt->timer, jiffies + min_heartbeat);
> > +		/*
> > +		 * Use min_heartbeat the first time to avoid spurious watchdog
> reset:
> > +		 * we don't know for how long the watchdog counter is running,
> and
> > +		 *  - resetting it right now might trigger a watchdog fault reset
> > +		 *  - waiting for heartbeat time might lead to a watchdog timeout
> > +		 *    reset
> > +		 */
> > +		mod_timer(&wdt->timer, jiffies + min_heartbeat);
> > +	}
> >
> >   	/* Try to set timeout from device tree first */
> >   	if (watchdog_init_timeout(&wdt->wdd, 0, dev)) @@ -239,12 +314,14 @@
> > static int at91_wdt_init(struct platform_device *pdev, struct at91wdt *wdt)
> >   	if (err)
> >   		goto out_stop_timer;
> >
> > -	wdt->next_heartbeat = jiffies + wdt->wdd.timeout * HZ;
> > +	if (wdt->use_timer)
> > +		wdt->next_heartbeat = jiffies + wdt->wdd.timeout * HZ;
> >
> >   	return 0;
> >
> >   out_stop_timer:
> > -	del_timer(&wdt->timer);
> > +	if (wdt->use_timer)
> > +		del_timer(&wdt->timer);
> >   	return err;
> >   }
> >
> > @@ -256,13 +333,54 @@ static const struct watchdog_info at91_wdt_info = {
> >   						WDIOF_MAGICCLOSE,
> >   };
> >
> > -static const struct watchdog_ops at91_wdt_ops = {
> > +static struct watchdog_ops at91_wdt_ops = {
> >   	.owner =	THIS_MODULE,
> >   	.start =	at91_wdt_start,
> >   	.stop =		at91_wdt_stop,
> >   	.set_timeout =	at91_wdt_set_timeout,
> >   };
> >
> > +static const struct at91wdt_variant drv_data_at91sam9260 = {
> > +	.mr_writable = false,
> > +};
> > +
> > +#if defined(CONFIG_OF)
> > +static const struct at91wdt_variant drv_data_sama5d4 = {
> > +	.mr_writable = true,
> > +};
> > +
> > +static const struct of_device_id at91_wdt_dt_ids[] = {
> > +	{ .compatible = "atmel,at91sam9260-wdt",
> > +	  .data = &drv_data_at91sam9260 },
> > +	{ .compatible = "atmel,sama5d4-wdt",
> > +	  .data = &drv_data_sama5d4 },
> > +	{ /* sentinel */ }
> > +};
> > +MODULE_DEVICE_TABLE(of, at91_wdt_dt_ids); #endif
> > +
> > +static const struct platform_device_id at91wdt_ids[] = {
> > +	{
> > +		.name = "at91_wdt",
> > +		.driver_data = (unsigned long)&drv_data_at91sam9260,
> > +	},
> > +	{}
> > +};
> > +MODULE_DEVICE_TABLE(platform, at91wdt_ids);
> > +
> > +static struct at91wdt_variant *at91wdt_get_drv_data(struct
> > +platform_device *pdev) {
> > +	const struct of_device_id *match;
> > +
> > +	if (pdev->dev.of_node) {
> > +		match = of_match_node(at91_wdt_dt_ids, pdev->dev.of_node);
> > +		return (struct at91wdt_variant *)match->data;
> > +	} else {
> > +		return (struct at91wdt_variant *)
> > +			platform_get_device_id(pdev)->driver_data;
> > +	}
> > +}
> > +
> >   #if defined(CONFIG_OF)
> >   static int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
> >   {
> > @@ -336,6 +454,10 @@ static int __init at91wdt_probe(struct platform_device
> *pdev)
> >   	if (!wdt)
> >   		return -ENOMEM;
> >
> > +	wdt->drv_data = at91wdt_get_drv_data(pdev);
> > +	if (wdt->drv_data->mr_writable)
> > +		at91_wdt_ops.ping = at91_wdt_ping;
> > +
> >   	wdt->mr = (WDT_HW_TIMEOUT * 256) | AT91_WDT_WDRSTEN |
> AT91_WDT_WDD |
> >   		  AT91_WDT_WDDBGHLT | AT91_WDT_WDIDLEHLT;
> >   	wdt->mr_mask = 0x3FFFFFFF;
> > @@ -364,8 +486,12 @@ static int __init at91wdt_probe(struct
> > platform_device *pdev)
> >
> >   	platform_set_drvdata(pdev, wdt);
> >
> > -	pr_info("enabled (heartbeat=%d sec, nowayout=%d)\n",
> > -		wdt->wdd.timeout, wdt->nowayout);
> > +	if (wdt->enabled) {
> > +		dev_info(&pdev->dev, "enabled (heartbeat=%d sec,
> nowayout=%d)\n",
> > +			wdt->wdd.timeout, wdt->nowayout);
> > +	} else {
> > +		dev_info(&pdev->dev, "not enabled\n");
> > +	}
> >
> >   	return 0;
> >   }
> > @@ -381,15 +507,6 @@ static int __exit at91wdt_remove(struct
> platform_device *pdev)
> >   	return 0;
> >   }
> >
> > -#if defined(CONFIG_OF)
> > -static const struct of_device_id at91_wdt_dt_ids[] = {
> > -	{ .compatible = "atmel,at91sam9260-wdt" },
> > -	{ /* sentinel */ }
> > -};
> > -
> > -MODULE_DEVICE_TABLE(of, at91_wdt_dt_ids); -#endif
> > -
> >   static struct platform_driver at91wdt_driver = {
> >   	.remove		= __exit_p(at91wdt_remove),
> >   	.driver		= {
> > diff --git a/drivers/watchdog/at91sam9_wdt.h
> > b/drivers/watchdog/at91sam9_wdt.h index c6fbb2e6..79add4f 100644
> > --- a/drivers/watchdog/at91sam9_wdt.h
> > +++ b/drivers/watchdog/at91sam9_wdt.h
> > @@ -22,11 +22,15 @@
> >
> >   #define AT91_WDT_MR		0x04			/* Watchdog
> Mode Register */
> >   #define		AT91_WDT_WDV		(0xfff << 0)		/*
> Counter Value */
> > +#define			AT91_WDT_WDV_MSK	(0xfff)
> > +#define			AT91_WDT_WDV_(x)	(((x) &
> AT91_WDT_WDV_MSK) << 0)
> >   #define		AT91_WDT_WDFIEN		(1     << 12)		/*
> Fault Interrupt Enable */
> >   #define		AT91_WDT_WDRSTEN	(1     << 13)		/*
> Reset Processor */
> >   #define		AT91_WDT_WDRPROC	(1     << 14)		/*
> Timer Restart */
> >   #define		AT91_WDT_WDDIS		(1     << 15)		/*
> Watchdog Disable */
> >   #define		AT91_WDT_WDD		(0xfff << 16)		/*
> Delta Value */
> > +#define			AT91_WDT_WDD_MSK	(0xfff)
> > +#define			AT91_WDT_WDD_(x)	(((x) &
> AT91_WDT_WDD_MSK) << 16)
> >   #define		AT91_WDT_WDDBGHLT	(1     << 28)		/*
> Debug Halt */
> >   #define		AT91_WDT_WDIDLEHLT	(1     << 29)		/*
> Idle Halt */
> >
> >


Best Regards,
Wenyou Yang

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