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Sender: Guenter Roeck <groeck7@gmail.com>
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Date: Tue, 26 Mar 2024 08:28:52 -0700
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Subject: Re: [PATCH v3 4/4] drivers: watchdog: ast2500 and ast2600 support
 bootstatus
Content-Language: en-US
To: Peter Yin <peteryin.openbmc@gmail.com>, patrick@stwcx.xyz,
 Wim Van Sebroeck <wim@linux-watchdog.org>, Rob Herring <robh@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
 Conor Dooley <conor+dt@kernel.org>, Joel Stanley <joel@jms.id.au>,
 Andrew Jeffery <andrew@codeconstruct.com.au>,
 linux-watchdog@vger.kernel.org, devicetree@vger.kernel.org,
 linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org,
 linux-kernel@vger.kernel.org
References: <20240326150027.3015958-1-peteryin.openbmc@gmail.com>
 <20240326150027.3015958-5-peteryin.openbmc@gmail.com>
From: Guenter Roeck <linux@roeck-us.net>
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In-Reply-To: <20240326150027.3015958-5-peteryin.openbmc@gmail.com>
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On 3/26/24 08:00, Peter Yin wrote:
> Add WDIOF_EXTERN1 and WDIOF_CARDRESET bootstatus in ast2600
> 
> Regarding the AST2600 specification, the WDTn Timeout Status Register
> (WDT10) has bit 1 reserved. Bit 1 of the status register indicates
> on ast2500 if the boot was from the second boot source.
> It does not indicate that the most recent reset was triggered by
> the watchdog. The code should just be changed to set WDIOF_CARDRESET
> if bit 0 of the status register is set.
> 
> Include SCU register to veriy WDIOF_EXTERN1 in ast2600 SCU74 or
> ast2500 SCU3C when bit1 is set.
> 
> Signed-off-by: Peter Yin <peteryin.openbmc@gmail.com>
> ---
>   drivers/watchdog/aspeed_wdt.c | 53 ++++++++++++++++++++++++-----------
>   1 file changed, 37 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
> index b4773a6aaf8c..52afc5240b1c 100644
> --- a/drivers/watchdog/aspeed_wdt.c
> +++ b/drivers/watchdog/aspeed_wdt.c
> @@ -11,10 +11,12 @@
>   #include <linux/io.h>
>   #include <linux/kernel.h>
>   #include <linux/kstrtox.h>
> +#include <linux/mfd/syscon.h>
>   #include <linux/module.h>
>   #include <linux/of.h>
>   #include <linux/of_irq.h>
>   #include <linux/platform_device.h>
> +#include <linux/regmap.h>
>   #include <linux/watchdog.h>
>   
>   static bool nowayout = WATCHDOG_NOWAYOUT;
> @@ -65,23 +67,32 @@ MODULE_DEVICE_TABLE(of, aspeed_wdt_of_table);
>   #define WDT_RELOAD_VALUE	0x04
>   #define WDT_RESTART		0x08
>   #define WDT_CTRL		0x0C
> -#define   WDT_CTRL_BOOT_SECONDARY	BIT(7)
> -#define   WDT_CTRL_RESET_MODE_SOC	(0x00 << 5)
> -#define   WDT_CTRL_RESET_MODE_FULL_CHIP	(0x01 << 5)
> -#define   WDT_CTRL_RESET_MODE_ARM_CPU	(0x10 << 5)
> -#define   WDT_CTRL_1MHZ_CLK		BIT(4)
> -#define   WDT_CTRL_WDT_EXT		BIT(3)
> -#define   WDT_CTRL_WDT_INTR		BIT(2)
> -#define   WDT_CTRL_RESET_SYSTEM		BIT(1)
> -#define   WDT_CTRL_ENABLE		BIT(0)
> +#define WDT_CTRL_BOOT_SECONDARY	BIT(7)
> +#define WDT_CTRL_RESET_MODE_SOC	(0x00 << 5)
> +#define WDT_CTRL_RESET_MODE_FULL_CHIP	(0x01 << 5)
> +#define WDT_CTRL_RESET_MODE_ARM_CPU	(0x10 << 5)
> +#define WDT_CTRL_1MHZ_CLK		BIT(4)
> +#define WDT_CTRL_WDT_EXT		BIT(3)
> +#define WDT_CTRL_WDT_INTR		BIT(2)
> +#define WDT_CTRL_RESET_SYSTEM		BIT(1)
> +#define WDT_CTRL_ENABLE		BIT(0)
>   #define WDT_TIMEOUT_STATUS	0x10
> -#define   WDT_TIMEOUT_STATUS_IRQ		BIT(2)
> -#define   WDT_TIMEOUT_STATUS_BOOT_SECONDARY	BIT(1)
> +#define WDT_TIMEOUT_STATUS_IRQ		BIT(2)
> +#define WDT_TIMEOUT_STATUS_BOOT_SECONDARY	BIT(1)
> +#define WDT_TIMEOUT_STATUS_EVENT		BIT(0)
>   #define WDT_CLEAR_TIMEOUT_STATUS	0x14
> -#define   WDT_CLEAR_TIMEOUT_AND_BOOT_CODE_SELECTION	BIT(0)
> +#define WDT_CLEAR_TIMEOUT_AND_BOOT_CODE_SELECTION	BIT(0)
>   #define WDT_RESET_MASK1		0x1c
>   #define WDT_RESET_MASK2		0x20
>   
> +/*
> + * Ast2600 SCU74 bit1 is External reset flag
> + * Ast2500 SCU3C bit1 is External reset flag
> + */
> +#define   EXTERN_RESET_FLAG		BIT(1)
> +#define   AST2500_SYSTEM_RESET_EVENT	(0x3C)
> +#define   AST2600_SYSTEM_RESET_EVENT	(0x74)

() around constants does not add any value.

> +
>   /*
>    * WDT_RESET_WIDTH controls the characteristics of the external pulse (if
>    * enabled), specifically:
> @@ -458,15 +469,25 @@ static int aspeed_wdt_probe(struct platform_device *pdev)
>   		writel(duration - 1, wdt->base + WDT_RESET_WIDTH);
>   	}
>   
> +	struct regmap *scu_base = syscon_regmap_lookup_by_phandle(dev->of_node,
> +							     "aspeed,scu");
>   	status = readl(wdt->base + WDT_TIMEOUT_STATUS);
> -	if (status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY) {
> +	if (status & WDT_TIMEOUT_STATUS_EVENT)
>   		wdt->wdd.bootstatus = WDIOF_CARDRESET;
>   
> -		if (of_device_is_compatible(np, "aspeed,ast2400-wdt") ||
> -		    of_device_is_compatible(np, "aspeed,ast2500-wdt"))
> -			wdt->wdd.groups = bswitch_groups;
> +	if (of_device_is_compatible(np, "aspeed,ast2600-wdt")) {
> +		regmap_read(scu_base, AST2600_SYSTEM_RESET_EVENT, &status);

scu_base as returned from syscon_regmap_lookup_by_phandle() can be an ERR_PTR.
If it is, this will crash. On top of ttat, regmap_read() can also return an
error. If it does, status will be unmodified, and WDIOF_EXTERN1 will be set randomly.
This will most definitely happen if REGMAP support is disabled (there is nothing
in Kconfig requiring that REGMAP must be enabled for this driver).

Guenter