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From:   Anson Huang <anson.huang@nxp.com>
To:     Guenter Roeck <linux@roeck-us.net>
CC:     "wim@linux-watchdog.org" <wim@linux-watchdog.org>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
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        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: RE: [PATCH V3 1/2] watchdog: imx7ulp: Strictly follow the sequence
 for wdog operations
Thread-Topic: [PATCH V3 1/2] watchdog: imx7ulp: Strictly follow the sequence
 for wdog operations
Thread-Index: AQHWZhYvIsu3X7R3l0CXWRnCv98krqkgV38AgABjQnA=
Date:   Thu, 30 Jul 2020 22:48:42 +0000
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 <20200730165240.GA178323@roeck-us.net>
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Hi, Guenter


> Subject: Re: [PATCH V3 1/2] watchdog: imx7ulp: Strictly follow the sequen=
ce
> for wdog operations
>=20
> On Thu, Jul 30, 2020 at 10:03:10AM +0800, Anson Huang wrote:
> > According to reference manual, the i.MX7ULP WDOG's operations except
> > refresh should follow below sequence:
> >
> > 1. disable global interrupts;
> > 2. unlock the wdog and wait unlock bit set; 3. reconfigure the wdog
> > and wait for reconfiguration bit set; 4. enabel global interrupts.
> >
> > Strictly follow the recommended sequence can make it more robust.
> >
> > Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
> > ---
> > changes since V2:
> > 	- change the wait timeout to 20us according to experiment;
> > 	- drop WARN_ON when timeout, and check its return value in each caller
> for
> > 	  unlock wait, no need to handle the return value for reconfiguration.
> > ---
> >  drivers/watchdog/imx7ulp_wdt.c | 74
> > ++++++++++++++++++++++++++++++++++--------
> >  1 file changed, 61 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/watchdog/imx7ulp_wdt.c
> > b/drivers/watchdog/imx7ulp_wdt.c index 7993c8c..010ddd1 100644
> > --- a/drivers/watchdog/imx7ulp_wdt.c
> > +++ b/drivers/watchdog/imx7ulp_wdt.c
> > @@ -5,6 +5,7 @@
> >
> >  #include <linux/clk.h>
> >  #include <linux/io.h>
> > +#include <linux/iopoll.h>
> >  #include <linux/kernel.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> > @@ -36,6 +37,7 @@
> >  #define DEFAULT_TIMEOUT	60
> >  #define MAX_TIMEOUT	128
> >  #define WDOG_CLOCK_RATE	1000
> > +#define WDOG_WAIT_TIMEOUT	20
> >
> >  static bool nowayout =3D WATCHDOG_NOWAYOUT;
> module_param(nowayout,
> > bool, 0000); @@ -48,17 +50,40 @@ struct imx7ulp_wdt_device {
> >  	struct clk *clk;
> >  };
> >
> > -static void imx7ulp_wdt_enable(struct watchdog_device *wdog, bool
> > enable)
> > +static int imx7ulp_wdt_wait(void __iomem *base, u32 mask) {
> > +	u32 val =3D readl(base + WDOG_CS);
> > +
> > +	if (!(val & mask) && readl_poll_timeout_atomic(base + WDOG_CS, val,
> > +						       val & mask, 0,
> > +						       WDOG_WAIT_TIMEOUT))
> > +		return -ETIMEDOUT;
> > +
> > +	return 0;
> > +}
> > +
> > +static int imx7ulp_wdt_enable(struct watchdog_device *wdog, bool
> > +enable)
> >  {
> >  	struct imx7ulp_wdt_device *wdt =3D watchdog_get_drvdata(wdog);
> >
> >  	u32 val =3D readl(wdt->base + WDOG_CS);
> > +	int ret;
> >
> > +	local_irq_disable();
> >  	writel(UNLOCK, wdt->base + WDOG_CNT);
> > +	ret =3D imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK);
> > +	if (ret)
> > +		goto enable_out;
> >  	if (enable)
> >  		writel(val | WDOG_CS_EN, wdt->base + WDOG_CS);
> >  	else
> >  		writel(val & ~WDOG_CS_EN, wdt->base + WDOG_CS);
> > +	imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS);
> > +
> > +enable_out:
> > +	local_irq_enable();
> > +
> > +	return ret;
> >  }
> >
> >  static bool imx7ulp_wdt_is_enabled(void __iomem *base) @@ -79,17
> > +104,12 @@ static int imx7ulp_wdt_ping(struct watchdog_device *wdog)
> >
> >  static int imx7ulp_wdt_start(struct watchdog_device *wdog)  {
> > -
> > -	imx7ulp_wdt_enable(wdog, true);
> > -
> > -	return 0;
> > +	return imx7ulp_wdt_enable(wdog, true);
> >  }
> >
> >  static int imx7ulp_wdt_stop(struct watchdog_device *wdog)  {
> > -	imx7ulp_wdt_enable(wdog, false);
> > -
> > -	return 0;
> > +	return imx7ulp_wdt_enable(wdog, false);
> >  }
> >
> >  static int imx7ulp_wdt_set_timeout(struct watchdog_device *wdog, @@
> > -97,22 +117,37 @@ static int imx7ulp_wdt_set_timeout(struct
> > watchdog_device *wdog,  {
> >  	struct imx7ulp_wdt_device *wdt =3D watchdog_get_drvdata(wdog);
> >  	u32 val =3D WDOG_CLOCK_RATE * timeout;
> > +	int ret;
> >
> > +	local_irq_disable();
> >  	writel(UNLOCK, wdt->base + WDOG_CNT);
> > +	ret =3D imx7ulp_wdt_wait(wdt->base, WDOG_CS_ULK);
> > +	if (ret)
> > +		goto timeout_out;
> >  	writel(val, wdt->base + WDOG_TOVAL);
> > +	imx7ulp_wdt_wait(wdt->base, WDOG_CS_RCS);
> > +
> > +timeout_out:
> > +	local_irq_enable();
> >
> >  	wdog->timeout =3D timeout;
>=20
> This needs to be moved up - the timeout did not get changed on error.

Ah, yes, will fix it in V4.

Thanks,
Anson