Re: [PATCH v6 1/1] watchdog: aspeed: Update bootstatus handling

[Andrew Jeffery <andrew@codeconstruct.com.au>]

On Sun, 2025-01-12 at 16:12 +0800, Chin-Ting Kuo wrote:
> The boot status in the watchdog device struct is updated during
> controller probe stage. Application layer can get the boot status
> through the command, cat /sys/class/watchdog/watchdogX/bootstatus.
> The bootstatus can be,
> WDIOF_CARDRESET => the system is reset by WDT SoC reset.
> Others          => other reset events, e.g., power on reset.
> 
> On ASPEED platform, the boot status is recorded in the SCU registers.
> - AST2400: Only a bit represents for any WDT reset.
> - AST2500/AST2600: The reset triggered by different WDT controllers
>                    can be distinguished by different SCU bits.
> 
> Besides, on AST2400 and AST2500, since alternating boot event is
> triggered by WDT SoC reset, it is classified as WDIOF_CARDRESET.
> 
> Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
> ---
>  drivers/watchdog/aspeed_wdt.c | 81
> ++++++++++++++++++++++++++++++++++-
>  1 file changed, 79 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/watchdog/aspeed_wdt.c
> b/drivers/watchdog/aspeed_wdt.c
> index b4773a6aaf8c..369635b38ca0 100644
> --- a/drivers/watchdog/aspeed_wdt.c
> +++ b/drivers/watchdog/aspeed_wdt.c
> @@ -11,21 +11,30 @@
>  #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;
>  module_param(nowayout, bool, 0);
>  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started
> (default="
>                                 __MODULE_STRING(WATCHDOG_NOWAYOUT)
> ")");
> +struct aspeed_wdt_scu {
> +       const char *compatible;
> +       u32 reset_status_reg;
> +       u32 wdt_reset_mask;
> +       u32 wdt_reset_mask_shift;
> +};
>  
>  struct aspeed_wdt_config {
>         u32 ext_pulse_width_mask;
>         u32 irq_shift;
>         u32 irq_mask;
> +       struct aspeed_wdt_scu scu;
>  };
>  
>  struct aspeed_wdt {
> @@ -39,18 +48,36 @@ static const struct aspeed_wdt_config
> ast2400_config = {
>         .ext_pulse_width_mask = 0xff,
>         .irq_shift = 0,
>         .irq_mask = 0,
> +       .scu = {
> +               .compatible = "aspeed,ast2400-scu",
> +               .reset_status_reg = 0x3c,
> +               .wdt_reset_mask = 0x1,
> +               .wdt_reset_mask_shift = 1,
> +       },
>  };
>  
>  static const struct aspeed_wdt_config ast2500_config = {
>         .ext_pulse_width_mask = 0xfffff,
>         .irq_shift = 12,
>         .irq_mask = GENMASK(31, 12),
> +       .scu = {
> +               .compatible = "aspeed,ast2500-scu",
> +               .reset_status_reg = 0x3c,
> +               .wdt_reset_mask = 0x1,
> +               .wdt_reset_mask_shift = 2,
> +       },
>  };
>  
>  static const struct aspeed_wdt_config ast2600_config = {
>         .ext_pulse_width_mask = 0xfffff,
>         .irq_shift = 0,
>         .irq_mask = GENMASK(31, 10),
> +       .scu = {
> +               .compatible = "aspeed,ast2600-scu",
> +               .reset_status_reg = 0x74,
> +               .wdt_reset_mask = 0xf,
> +               .wdt_reset_mask_shift = 16,
> +       },
>  };
>  
>  static const struct of_device_id aspeed_wdt_of_table[] = {
> @@ -213,6 +240,56 @@ static int aspeed_wdt_restart(struct
> watchdog_device *wdd,
>         return 0;
>  }
>  
> +static void aspeed_wdt_update_bootstatus(struct platform_device
> *pdev,
> +                                        struct aspeed_wdt *wdt)
> +{
> +       const struct resource *res;
> +       struct aspeed_wdt_scu scu = wdt->cfg->scu;
> +       struct regmap *scu_base;
> +       u32 reset_mask_width;
> +       u32 reset_mask_shift;
> +       u32 idx = 0;
> +       u32 status;
> +       int ret;
> +
> +       if (!of_device_is_compatible(pdev->dev.of_node,
> "aspeed,ast2400-wdt")) {
> +               res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +               idx = ((intptr_t)wdt->base & 0x00000fff) /
> resource_size(res);
> +       }
> +
> +       scu_base =
> syscon_regmap_lookup_by_compatible(scu.compatible);
> +       if (IS_ERR(scu_base)) {
> +               wdt->wdd.bootstatus = WDIOS_UNKNOWN;
> +               return;
> +       }
> +
> +       ret = regmap_read(scu_base, scu.reset_status_reg, &status);
> +       if (ret) {
> +               wdt->wdd.bootstatus = WDIOS_UNKNOWN;
> +               return;
> +       }
> +
> +       reset_mask_width = hweight32(scu.wdt_reset_mask);
> +       reset_mask_shift = scu.wdt_reset_mask_shift +
> +                          reset_mask_width * idx;
> +
> +       if (status & (scu.wdt_reset_mask << reset_mask_shift))
> +               wdt->wdd.bootstatus = WDIOF_CARDRESET;

How precise is the wording in your commit message? The AST2600, for
instance, has 4 reset types:

1. "SoC"
2. "Full"
3. "ARM"
4. "Software"

In the commit message, you said:

> WDIOF_CARDRESET => the system is reset by WDT SoC reset.

However the logic here (with the way you've initialised the config
struct for the AST2600) will signal WDIOF_CARDRESET even if what
occurred was e.g. a (graceful?) software reset.

The only thing WDIOF_CARDRESET differentiates is a power-on reset from
any other kind of watchdog-driven reset.

Is that what's intended? I'm just wary of confusion for what appears to
be a generic use of "SoC" in the commit message vs the specific "SoC"
mode of the watchdog controller (should some documentation be
written/updated?)

Andrew