Re: Forcing non-ACPI watchdog driver

[Jean Delvare <jdelvare@suse.de>]

Hi Mika,

On Wed, 5 Feb 2020 18:38:31 +0200, Mika Westerberg wrote:
> On Wed, Feb 05, 2020 at 08:30:48AM -0800, Guenter Roeck wrote:
> > On Wed, Feb 05, 2020 at 05:24:35PM +0200, Mika Westerberg wrote:  
> > > You should be able to revert to iTCO_wdt by simply disabling
> > > CONFIG_WDAT_WDT from .config. Then acpi_has_watchdog() returns false
> > > which means that iTCO_wdt is used instead.  
> > 
> > That may not be possible in a generic distribution.  
> 
> Right, they would need to build their own kernel. Currently there is no
> way to do that without changing .config.

OK, that's pretty much what I was compl^Wworried about ;-) Would you
consider applying something like the following patch?

From: Jean Delvare <jdelvare@suse.de>
Subject: ACPI / watchdog: Allow disabling WDAT at boot

In case the WDAT interface is broken, give the user the option to
ignore it to let a native driver bind to the watchdog device instead.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 Documentation/admin-guide/kernel-parameters.txt |    4 ++++
 drivers/acpi/acpi_watchdog.c                    |   12 +++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

--- linux-5.4.orig/drivers/acpi/acpi_watchdog.c	2020-02-06 15:20:27.187333079 +0100
+++ linux-5.4/drivers/acpi/acpi_watchdog.c	2020-02-06 15:30:08.707408406 +0100
@@ -55,12 +55,14 @@ static bool acpi_watchdog_uses_rtc(const
 }
 #endif
 
+static bool acpi_no_watchdog;
+
 static const struct acpi_table_wdat *acpi_watchdog_get_wdat(void)
 {
 	const struct acpi_table_wdat *wdat = NULL;
 	acpi_status status;
 
-	if (acpi_disabled)
+	if (acpi_disabled || acpi_no_watchdog)
 		return NULL;
 
 	status = acpi_get_table(ACPI_SIG_WDAT, 0,
@@ -88,6 +90,14 @@ bool acpi_has_watchdog(void)
 }
 EXPORT_SYMBOL_GPL(acpi_has_watchdog);
 
+/* ACPI watchdog can be disabled on boot command line */
+static int __init disable_acpi_watchdog(char *str)
+{
+	acpi_no_watchdog = true;
+	return 1;
+}
+__setup("acpi_no_watchdog", disable_acpi_watchdog);
+
 void __init acpi_watchdog_init(void)
 {
 	const struct acpi_wdat_entry *entries;
--- linux-5.4.orig/Documentation/admin-guide/kernel-parameters.txt	2020-02-06 15:20:27.187333079 +0100
+++ linux-5.4/Documentation/admin-guide/kernel-parameters.txt	2020-02-06 15:31:16.614155680 +0100
@@ -136,6 +136,10 @@
 			dynamic table installation which will install SSDT
 			tables to /sys/firmware/acpi/tables/dynamic.
 
+	acpi_no_watchdog	[HW,ACPI,WDT]
+			Ignore the ACPI-based watchdog interface (WDAT) and let
+			a native driver control the watchdog device instead.
+
 	acpi_rsdp=	[ACPI,EFI,KEXEC]
 			Pass the RSDP address to the kernel, mostly used
 			on machines running EFI runtime service to boot the

Thanks,
-- 
Jean Delvare
SUSE L3 Support