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

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Date:   Thu, 28 Apr 2022 08:29:52 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Pali Rohár <pali@...nel.org>
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 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.

>>> 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().

>>> +		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.

>>> +
>>>    	err = max63xx_mmap_init(pdev, wdt);

Doesn't this override the gpio ping function set above ?

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