[PATCH 2/2] platform: sifive_fu740: fix reset when watchdog is running

[Nikita Shubin <nikita.shubin@maquefel.me>]

Hello Aurelien!

Adding David from SiFive...

On Wed,  5 Jan 2022 08:20:39 +0100
Aurelien Jarno <aurelien@aurel32.net> wrote:

> When the watchdog is running the HiFive Unmatched board does not
> reboot properly and shuts down itself a few seconds after reboot, in
> the early stages of the u-boot loading. On a Linux kernel this
> happens when the da9063_wdt module is loaded. This does not happen if
> the module is unloaded before reboot or if the watchdog module is
> loaded with "stop_on_reboot=1".

| A running application is typically in ACTIVE mode. The DA9063
| transitions to ACTIVE mode after the host processor performs at least
| one initial ?alive? watchdog write (or alternatively an initial
| assertion of the KEEP_ACT port) inside the target time window. If the
| WATCHDOG function is disabled by setting TWDSCALE to zero, the DA9063
| transitions to ACTIVE mode when all of the sequencer IDs in the POWER
| domain are complete.

Is this that's case mentioned ? What if we press a reset key when
watchdog is enabled ? Or if it was reseted by thermal sensor ?

Can we disable watchdog on start instead of disabling it before a reset
?

Could you please give us a link to actual report ?

> 
> Fix that by stopping the watchdog before attempting to reset the
> board. This is done by zeroing the TWDSCALE field of CONTROL_D
> register, unless it was already set to 0.
> 
> Reported-by: Tianon Gravi <tianon@debian.org>
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
> ---
>  platform/generic/sifive_fu740.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/platform/generic/sifive_fu740.c
> b/platform/generic/sifive_fu740.c index 866e924..f595c04 100644
> --- a/platform/generic/sifive_fu740.c
> +++ b/platform/generic/sifive_fu740.c
> @@ -22,6 +22,7 @@
>  
>  #define DA9063_REG_PAGE_CON		0x00
>  #define DA9063_REG_CONTROL_A		0x0e
> +#define DA9063_REG_CONTROL_D		0x11
>  #define DA9063_REG_CONTROL_F		0x13
>  #define DA9063_REG_DEVICE_ID		0x81
>  
> @@ -29,6 +30,8 @@
>  #define DA9063_CONTROL_A_M_POWER_EN	(1 << 5)
>  #define DA9063_CONTROL_A_STANDBY	(1 << 3)
>  
> +#define DA9063_CONTROL_D_TWDSCALE_MASK	0x07
> +
>  #define DA9063_CONTROL_F_WAKEUP	(1 << 2)
>  #define DA9063_CONTROL_F_SHUTDOWN	(1 << 1)
>  
> @@ -79,6 +82,27 @@ static inline int da9063_sanity_check(struct
> i2c_adapter *adap, uint32_t reg) return 0;
>  }
>  
> +static inline int da9063_stop_watchdog(struct i2c_adapter *adap,
> uint32_t reg) +{
> +	uint8_t val;
> +	int rc = i2c_adapter_reg_write(adap, reg,
> +					DA9063_REG_PAGE_CON, 0x00);
> +
> +	if (rc)
> +		return rc;
> +
> +	rc = i2c_adapter_reg_read(adap, reg, DA9063_REG_CONTROL_D,
> &val);
> +	if (rc)
> +		return rc;
> +
> +	if ((val & DA9063_CONTROL_D_TWDSCALE_MASK) == 0)
> +		return 0;
> +
> +	val &= ~DA9063_CONTROL_D_TWDSCALE_MASK;
> +
> +	return i2c_adapter_reg_write(adap, reg,
> DA9063_REG_CONTROL_D, val); +}
> +
>  static inline int da9063_shutdown(struct i2c_adapter *adap, uint32_t
> reg) {
>  	int rc = i2c_adapter_reg_write(adap, reg,
> @@ -133,6 +157,7 @@ static void da9063_system_reset(u32 type, u32
> reason) break;
>  		case SBI_SRST_RESET_TYPE_COLD_REBOOT:
>  		case SBI_SRST_RESET_TYPE_WARM_REBOOT:
> +			da9063_stop_watchdog(adap, reg);
>  			da9063_reset(adap, reg);
>  			break;
>  		}