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

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

On Mon, 2025-01-13 at 03:41 +0000, Chin-Ting Kuo wrote:
> Hi Andrew,
> 
> > -----Original Message-----
> > From: Andrew Jeffery <andrew@codeconstruct.com.au>
> > Sent: Monday, January 13, 2025 11:29 AM
> > Subject: Re: [PATCH v6 1/1] watchdog: aspeed: Update bootstatus
> > handling
> > 
> > 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(WATC
> > HDOG_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.
> > 
> 
> The commit message should be changed for more precisely.
> "WDIOF_CARDRESET => the system is reset due to WDT timeout occurs."
> This change can be updated with a new patch version.
> 
> > 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.
> > 
> 
> As the discussion in the previous patch series, there is no consensus
> for graceful
> reset flag in WDT framework. Thus, this patch only distinguishes WDT
> reset from
> other reset reasons.
> 
> > The only thing WDIOF_CARDRESET differentiates is a power-on reset
> > from any
> > other kind of watchdog-driven reset.
> > 
> 
> Yes.
> 
> > 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?)
> > 
> 
> The commit message can be updated.

Okay, thanks.

Andrew