linux-kernel - Re: [PATCH 2/2] watchdog: sp5100_tco: Enable watchdog on Family 17h devices if disabled

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Date:   Thu, 10 Sep 2020 18:34:44 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>
Cc:     linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] watchdog: sp5100_tco: Enable watchdog on Family 17h
 devices if disabled

On 10.09.20 18:31, Guenter Roeck wrote:
> On Family 17h (Ryzen) devices, the WatchdogTmrEn bit of PmDecodeEn not only
> enables watchdog memory decoding at 0xfeb00000, it also enables the
> watchdog hardware itself. Use this information to enable the watchdog if
> it is not already enabled.
> 
> Cc: Jan Kiszka <jan.kiszka@...mens.com>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
>  drivers/watchdog/sp5100_tco.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/watchdog/sp5100_tco.c b/drivers/watchdog/sp5100_tco.c
> index 85e9664318c9..a730ecbf78cd 100644
> --- a/drivers/watchdog/sp5100_tco.c
> +++ b/drivers/watchdog/sp5100_tco.c
> @@ -17,6 +17,12 @@
>   *	    AMD Publication 51192 "AMD Bolton FCH Register Reference Guide"
>   *	    AMD Publication 52740 "BIOS and Kernel Developer’s Guide (BKDG)
>   *				for AMD Family 16h Models 30h-3Fh Processors"
> + *	    AMD Publication 55570-B1-PUB "Processor Programming Reference (PPR)
> + *				for AMD Family 17h Model 18h, Revision B1
> + *				Processors (PUB)
> + *	    AMD Publication 55772-A1-PUB "Processor Programming Reference (PPR)
> + *				for AMD Family 17h Model 20h, Revision A1
> + *				Processors (PUB)
>   */
>  
>  /*
> @@ -241,6 +247,18 @@ static int sp5100_tco_setupdevice(struct device *dev,
>  		break;
>  	case efch:
>  		dev_name = SB800_DEVNAME;
> +		/*
> +		 * On Family 17h devices, the EFCH_PM_DECODEEN_WDT_TMREN bit of
> +		 * EFCH_PM_DECODEEN not only enables the EFCH_PM_WDT_ADDR memory
> +		 * region, it also enables the watchdog itself.
> +		 */
> +		if (boot_cpu_data.x86 == 0x17) {
> +			val = sp5100_tco_read_pm_reg8(EFCH_PM_DECODEEN);
> +			if (!(val & EFCH_PM_DECODEEN_WDT_TMREN)) {
> +				sp5100_tco_update_pm_reg8(EFCH_PM_DECODEEN, 0xff,
> +							  EFCH_PM_DECODEEN_WDT_TMREN);
> +			}
> +		}
>  		val = sp5100_tco_read_pm_reg8(EFCH_PM_DECODEEN);
>  		if (val & EFCH_PM_DECODEEN_WDT_TMREN)
>  			mmio_addr = EFCH_PM_WDT_ADDR;
> 

Won't that bring us EFCH_PM_WDT_ADDR as address, rather than
EFCH_PM_ACPI_MMIO_ADDR which worked in my case? Or is one an alias of
the other.

Jan

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