linux-kernel - Re: [PATCH] watchdog: max63xx_wdt: Add support for specifying WDI logic via GPIO

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Message-ID: <20220428182513.ava4ebkdclmxlf3b@pali>
Date:   Thu, 28 Apr 2022 20:25:13 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-watchdog@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: max63xx_wdt: Add support for specifying WDI
 logic via GPIO

On Thursday 28 April 2022 08:29:52 Guenter Roeck wrote:
> On 4/28/22 07:32, Pali Rohár wrote:
> > On Thursday 28 April 2022 06:10:56 Guenter Roeck wrote:
> > > On 4/28/22 02:16, Pali Rohár wrote:
> > > > On some boards is WDI logic of max6370 chip connected via GPIO. So extend
> > > > max63xx_wdt driver and DTS schema to allow specifying WDI logic via GPIO.
> > > > 
> > > > Signed-off-by: Pali Rohár <pali@...nel.org>
> > > 
> > > How is that different to just using the gpio watchdog driver ?
> > 
> > GPIO watchdog driver does not support max6370 memory mapped
> > configuration.
> > 
> > With this change, max6370 can use memory mapped space for watchdog
> > configuration and GPIO WDI for pinging.
> > 
> 
> Ok, that makes sense. Comments below.
> 
> Thanks,
> Guenter
> 
> > > Guenter
> > > 
> > > > ---
> > > >    .../bindings/watchdog/maxim,max63xx.yaml      |  4 +++
> > > >    drivers/watchdog/max63xx_wdt.c                | 28 +++++++++++++++++++
> > > >    2 files changed, 32 insertions(+)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml b/Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml
> > > > index ab9641e845db..a97aa0135ef9 100644
> > > > --- a/Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml
> > > > +++ b/Documentation/devicetree/bindings/watchdog/maxim,max63xx.yaml
> > > > @@ -27,6 +27,10 @@ properties:
> > > >        description: This is a 1-byte memory-mapped address
> > > >        maxItems: 1
> > > > +  gpios:
> > > > +    description: Optional GPIO used for controlling WDI when WDI bit is not mapped to memory
> > > > +    maxItems: 1
> > > > +
> > > >    required:
> > > >      - compatible
> > > >      - reg
> 
> Devicetree patches needs to be separate.

Ok.

> > > > diff --git a/drivers/watchdog/max63xx_wdt.c b/drivers/watchdog/max63xx_wdt.c
> > > > index 9e1541cfae0d..eaf00c3f06a5 100644
> > > > --- a/drivers/watchdog/max63xx_wdt.c
> > > > +++ b/drivers/watchdog/max63xx_wdt.c
> > > > @@ -27,6 +27,7 @@
> > > >    #include <linux/io.h>
> > > >    #include <linux/slab.h>
> > > >    #include <linux/property.h>
> > > > +#include <linux/gpio/consumer.h>
> > > >    #define DEFAULT_HEARTBEAT 60
> > > >    #define MAX_HEARTBEAT     60
> > > > @@ -53,6 +54,9 @@ struct max63xx_wdt {
> > > >    	void __iomem *base;
> > > >    	spinlock_t lock;
> > > > +	/* GPIOs */
> > > > +	struct gpio_desc *gpio_wdi;
> > > > +
> > > >    	/* WDI and WSET bits write access routines */
> > > >    	void (*ping)(struct max63xx_wdt *wdt);
> > > >    	void (*set)(struct max63xx_wdt *wdt, u8 set);
> > > > @@ -158,6 +162,17 @@ static const struct watchdog_info max63xx_wdt_info = {
> > > >    	.identity = "max63xx Watchdog",
> > > >    };
> > > > +static void max63xx_gpio_ping(struct max63xx_wdt *wdt)
> > > > +{
> > > > +	spin_lock(&wdt->lock);
> > > > +
> > > > +	gpiod_set_value_cansleep(wdt->gpio_wdi, 1);
> > > > +	udelay(1);
> > > > +	gpiod_set_value_cansleep(wdt->gpio_wdi, 0);
> > > > +
> > > > +	spin_unlock(&wdt->lock);
> > > > +}
> > > > +
> > > >    static void max63xx_mmap_ping(struct max63xx_wdt *wdt)
> > > >    {
> > > >    	u8 val;
> > > > @@ -225,6 +240,19 @@ static int max63xx_wdt_probe(struct platform_device *pdev)
> > > >    		return -EINVAL;
> > > >    	}
> > > > +	wdt->gpio_wdi = devm_gpiod_get(dev, NULL, GPIOD_FLAGS_BIT_DIR_OUT);
> > > > +	if (IS_ERR(wdt->gpio_wdi) && PTR_ERR(wdt->gpio_wdi) != -ENOENT) {
> > > > +		if (PTR_ERR(wdt->gpio_wdi) != -EPROBE_DEFER)
> > > > +			dev_err(dev, "unable to request gpio: %ld\n",
> > > > +				PTR_ERR(wdt->gpio_wdi));
> 
> Please use dev_err_probe().

Ok.

> > > > +		return PTR_ERR(wdt->gpio_wdi);
> > > > +	}
> > > > +
> > > > +	if (!IS_ERR(wdt->gpio_wdi))
> > > > +		wdt->ping = max63xx_gpio_ping;
> > > > +	else
> > > > +		wdt->gpio_wdi = NULL;
> 
> Why set gpio_wdi to NULL? It isn't used if the ping function is not set.

I thought that it would be more safer to have NULL value stored in
pointer variable as opposite of some non-NULL value used for the error
reporting. But I can remove this part of the code.

> > > > +
> > > >    	err = max63xx_mmap_init(pdev, wdt);
> 
> Doesn't this override the gpio ping function set above ?

Yes, it does. I forgot to amend local change to this patch. wdt->ping
has to be changed to gpio_ping _after_ max63xx_mmap_init call.

I will fix all those issues in v2.

> > > >    	if (err)
> > > >    		return err;
> > > 
>