linux-kernel - Re: [PATCH] watchdog: da9062: make restart handler atomic safe

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Message-ID: <20200114173036.ueepbqf54yzh26lm@pengutronix.de>
Date:   Tue, 14 Jan 2020 18:30:36 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     support.opensource@...semi.com, contact@...fanchrist.eu,
        Adam.Thomson.Opensource@...semi.com,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de
Subject: Re: [PATCH] watchdog: da9062: make restart handler atomic safe

Hi,

On 20-01-13 12:28, Guenter Roeck wrote:
> On Mon, Jan 13, 2020 at 10:15:21AM +0100, Marco Felsch wrote:
> > The restart handler is executed during the shutdown phase which is
> > atomic/irq-less. The i2c framework supports atomic transfers since
> > commit 63b96983a5dd ("i2c: core: introduce callbacks for atomic
> > transfers") but unfortunately the regmap framework doesn't support it
> > yet. Hard coding the i2c stuff can be done without worries since the
> > DA9062 is an i2c-only device.
> > 
> > Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
> > ---
> > Hi,
> > 
> > This patch is based on Stefan Lengfeld's RFC Patch [1].
> > 
> > [1] https://patchwork.ozlabs.org/patch/1085942/
> > ---
> >  drivers/watchdog/da9062_wdt.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/watchdog/da9062_wdt.c b/drivers/watchdog/da9062_wdt.c
> > index c9b9d6394525..84c5a0a455b2 100644
> > --- a/drivers/watchdog/da9062_wdt.c
> > +++ b/drivers/watchdog/da9062_wdt.c
> > @@ -11,6 +11,7 @@
> >  #include <linux/platform_device.h>
> >  #include <linux/uaccess.h>
> >  #include <linux/slab.h>
> > +#include <linux/i2c.h>
> >  #include <linux/delay.h>
> >  #include <linux/jiffies.h>
> >  #include <linux/mfd/da9062/registers.h>
> > @@ -149,12 +150,18 @@ static int da9062_wdt_restart(struct watchdog_device *wdd, unsigned long action,
> >  			      void *data)
> >  {
> >  	struct da9062_watchdog *wdt = watchdog_get_drvdata(wdd);
> > +	struct i2c_client *client = to_i2c_client(wdt->hw->dev);
> > +	u8 buf[] = {DA9062AA_CONTROL_F, DA9062AA_SHUTDOWN_MASK};
> > +	struct i2c_msg msg = {
> > +		.addr = client->addr,
> > +		.flags = 0,
> > +		.len = sizeof(buf),
> > +		.buf = buf,
> > +	};
> >  	int ret;
> >  
> > -	ret = regmap_write(wdt->hw->regmap,
> > -			   DA9062AA_CONTROL_F,
> > -			   DA9062AA_SHUTDOWN_MASK);
> > -	if (ret)
> > +	ret = i2c_transfer(client->adapter, &msg, 1);
> 
> Why not i2c_smbus_write_byte_data() ? I don't immediately see the difference.

Because I didn't noticed it, sorry. I changed it and notice no
differences. Thanks for the review =)

Regards,
  Marco

> Guenter
> 
> > +	if (ret < 0)
> >  		dev_alert(wdt->hw->dev, "Failed to shutdown (err = %d)\n",
> >  			  ret);
> >  
> > -- 
> > 2.20.1
> >