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Date:   Thu, 13 Jul 2023 10:19:48 -0700
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To:     huaqian.li@siemens.com, wim@linux-watchdog.org, robh+dt@kernel.org,
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References: <20230713095127.1230109-1-huaqian.li@siemens.com>
 <20230713095127.1230109-4-huaqian.li@siemens.com>
From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH v3 3/3] watchdog:rit_wdt: Add support for WDIOF_CARDRESET
In-Reply-To: <20230713095127.1230109-4-huaqian.li@siemens.com>
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On 7/13/23 02:51, huaqian.li@siemens.com wrote:
> From: Li Hua Qian <huaqian.li@siemens.com>
> 
> This patch adds the WDIOF_CARDRESET support for the platform watchdog
> whose hardware does not support this feature, to know if the board
> reboot is due to a watchdog reset.
> 
> This is done via reserved memory(RAM), which indicates if specific
> info saved, triggering the watchdog reset in last boot.
> 
> Signed-off-by: Li Hua Qian <huaqian.li@siemens.com>
> ---
>   drivers/watchdog/rti_wdt.c | 51 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 51 insertions(+)
> 
> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
> index ce8f18e93aa9..b9435b972cb9 100644
> --- a/drivers/watchdog/rti_wdt.c
> +++ b/drivers/watchdog/rti_wdt.c
> @@ -18,6 +18,8 @@
>   #include <linux/pm_runtime.h>
>   #include <linux/types.h>
>   #include <linux/watchdog.h>
> +#include <linux/of_address.h>
> +#include <linux/of.h>
>   

This driver so far managed to keep include files in alphabetic order.
Please keep it that way.

>   #define DEFAULT_HEARTBEAT 60
>   
> @@ -52,6 +54,11 @@
>   
>   #define DWDST			BIT(1)
>   
> +#define PON_REASON_SOF_NUM	0xBBBBCCCC
> +#define PON_REASON_MAGIC_NUM	0xDDDDDDDD
> +#define PON_REASON_EOF_NUM	0xCCCCBBBB
> +#define RESERVED_MEM_MIN_SIZE	12
> +
>   static int heartbeat = DEFAULT_HEARTBEAT;
>   
>   /*
> @@ -198,6 +205,11 @@ static int rti_wdt_probe(struct platform_device *pdev)
>   	struct rti_wdt_device *wdt;
>   	struct clk *clk;
>   	u32 last_ping = 0;
> +	struct device_node *node;
> +	u32 reserved_mem_size;
> +	struct resource res;
> +	u32 *vaddr;
> +	u64 paddr;
>   
>   	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
>   	if (!wdt)
> @@ -284,6 +296,45 @@ static int rti_wdt_probe(struct platform_device *pdev)
>   		}
>   	}
>   
> +	node = of_parse_phandle(pdev->dev.of_node, "memory-region", 0);
> +	if (!node) {
> +		dev_dbg(dev, "No memory-region specified.\n");

If you really want that debug message, please keep the action part
first. I personally think it is just noise; the devicetree can always
be looked up if needed.

> +	} else {
> +		ret = of_address_to_resource(node, 0, &res);
> +		if (ret) {
> +			dev_err(dev, "No memory address assigned to the region.\n");
> +			goto err_iomap;
> +		}
> +
> +		/*
> +		 * If reserved memory is defined for watchdog reset cause.
> +		 * Readout the Power-on(PON) reason and pass to bootstatus.
> +		 */
> +		paddr = res.start;
> +		reserved_mem_size = res.end - (res.start - 1);

Please use resource_size().

> +		if (reserved_mem_size < RESERVED_MEM_MIN_SIZE) {
> +			dev_err(dev, "The size of reserved memory is too small.\n");
> +			ret = -EINVAL;
> +			goto err_iomap;
> +		}
> +
> +		vaddr = memremap(paddr, reserved_mem_size, MEMREMAP_WB);
> +		if (vaddr == NULL) {
> +			dev_err(dev, "Failed to map memory-region.\n");
> +			ret = -ENOMEM;
> +			goto err_iomap;
> +		}
> +
> +		if (vaddr[0] == PON_REASON_SOF_NUM &&
> +		    vaddr[1] == PON_REASON_MAGIC_NUM &&
> +		    vaddr[2] == PON_REASON_EOF_NUM) {
> +			dev_dbg(dev, "Watchdog reset cause detected.\n");

Isn't that a bit pointless ? That is obvious when reading the boot status.

> +			wdd->bootstatus |= WDIOF_CARDRESET;
> +		}
> +		memset(vaddr, 0, reserved_mem_size);
> +		memunmap(vaddr);
> +	}
> +
>   	watchdog_init_timeout(wdd, heartbeat, dev);
>   
>   	ret = watchdog_register_device(wdd);