[PATCH v3 0/4] pseries-wdt: initial support for H_WATCHDOG-based watchdog timers

[PATCH v3 0/4] pseries-wdt: initial support for H_WATCHDOG-based watchdog timers

[Scott Cheloha]

PAPR v2.12 defines a new hypercall, H_WATCHDOG.  This patch series
adds support for this hypercall to powerpc/pseries kernels and
introduces a new watchdog driver, "pseries-wdt", for the virtual
timers exposed by the hypercall.

This series is preceded by the following:

RFC v1: https://lore.kernel.org/linux-watchdog/20220413165104.179144-1-cheloha@linux.ibm.com/
RFC v2: https://lore.kernel.org/linux-watchdog/20220509174357.5448-1-cheloha@linux.ibm.com/
PATCH v1: https://lore.kernel.org/linux-watchdog/20220520183552.33426-1-cheloha@linux.ibm.com/
PATCH v2: https://lore.kernel.org/linux-watchdog/20220602175353.68942-1-cheloha@linux.ibm.com/

Changes of note from PATCH v2:

- Don't keep a pointer to the platform device at registration
  time.  We don't use the pointer for anything and we cannot
  hotplug the "device".

- Drop the GETFIELD() and SETFIELD() macros: Michael Ellerman really
  doesn't like them.  Use plain integer constants and custom bitfield
  extraction macros for the capability output instead.

  (After making the change I can see the upside to plain constants.)

- Actually use PSERIES_WDTQ_MAX_NUMBER(): check that the hypervisor
  gave us at least one timer to work with.

- Use MSEC_PER_SEC in a few places instead of the literal 1000 to
  show the reader what we're doing.

- Use "reverse xmas tree" sorting for automatic variable declarations.

- Note where the max_timeout of (UINT_MAX / 1000) comes from.

- Nix email addresses from the MODULE_AUTHOR() macros, they tend to
  rot.

[PATCH v3 1/4] powerpc/pseries: hvcall.h: add H_WATCHDOG opcode, H_NOOP return code

[Scott Cheloha]

PAPR v2.12 defines a new hypercall, H_WATCHDOG.  The hypercall permits
guest control of one or more virtual watchdog timers.

Add the opcode for the H_WATCHDOG hypercall to hvcall.h.  While here,
add a definition for H_NOOP, a possible return code for H_WATCHDOG.

Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
---
 arch/powerpc/include/asm/hvcall.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index d92a20a85395..4b4f69c35b4f 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -87,6 +87,7 @@
 #define H_P7		-60
 #define H_P8		-61
 #define H_P9		-62
+#define H_NOOP		-63
 #define H_TOO_BIG	-64
 #define H_UNSUPPORTED	-67
 #define H_OVERLAP	-68
@@ -324,7 +325,8 @@
 #define H_RPT_INVALIDATE	0x448
 #define H_SCM_FLUSH		0x44C
 #define H_GET_ENERGY_SCALE_INFO	0x450
-#define MAX_HCALL_OPCODE	H_GET_ENERGY_SCALE_INFO
+#define H_WATCHDOG		0x45C
+#define MAX_HCALL_OPCODE	H_WATCHDOG
 
 /* Scope args for H_SCM_UNBIND_ALL */
 #define H_UNBIND_SCOPE_ALL (0x1)
-- 
2.27.0

[PATCH v3 2/4] powerpc/pseries: add FW_FEATURE_WATCHDOG flag

[Scott Cheloha]

PAPR v2.12 specifies a new optional function set, "hcall-watchdog",
for the /rtas/ibm,hypertas-functions property.  The presence of this
function set indicates support for the H_WATCHDOG hypercall.

Check for this function set and, if present, set the new
FW_FEATURE_WATCHDOG flag.

Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
---
 arch/powerpc/include/asm/firmware.h       | 3 ++-
 arch/powerpc/platforms/pseries/firmware.c | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/firmware.h b/arch/powerpc/include/asm/firmware.h
index 8dddd34b8ecf..398e0b5e485f 100644
--- a/arch/powerpc/include/asm/firmware.h
+++ b/arch/powerpc/include/asm/firmware.h
@@ -55,6 +55,7 @@
 #define FW_FEATURE_RPT_INVALIDATE ASM_CONST(0x0000010000000000)
 #define FW_FEATURE_FORM2_AFFINITY ASM_CONST(0x0000020000000000)
 #define FW_FEATURE_ENERGY_SCALE_INFO ASM_CONST(0x0000040000000000)
+#define FW_FEATURE_WATCHDOG	ASM_CONST(0x0000080000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -76,7 +77,7 @@ enum {
 		FW_FEATURE_DRC_INFO | FW_FEATURE_BLOCK_REMOVE |
 		FW_FEATURE_PAPR_SCM | FW_FEATURE_ULTRAVISOR |
 		FW_FEATURE_RPT_INVALIDATE | FW_FEATURE_FORM2_AFFINITY |
-		FW_FEATURE_ENERGY_SCALE_INFO,
+		FW_FEATURE_ENERGY_SCALE_INFO | FW_FEATURE_WATCHDOG,
 	FW_FEATURE_PSERIES_ALWAYS = 0,
 	FW_FEATURE_POWERNV_POSSIBLE = FW_FEATURE_OPAL | FW_FEATURE_ULTRAVISOR,
 	FW_FEATURE_POWERNV_ALWAYS = 0,
diff --git a/arch/powerpc/platforms/pseries/firmware.c b/arch/powerpc/platforms/pseries/firmware.c
index 09c119b2f623..080108d129ed 100644
--- a/arch/powerpc/platforms/pseries/firmware.c
+++ b/arch/powerpc/platforms/pseries/firmware.c
@@ -67,6 +67,7 @@ hypertas_fw_features_table[] = {
 	{FW_FEATURE_PAPR_SCM,		"hcall-scm"},
 	{FW_FEATURE_RPT_INVALIDATE,	"hcall-rpt-invalidate"},
 	{FW_FEATURE_ENERGY_SCALE_INFO,	"hcall-energy-scale-info"},
+	{FW_FEATURE_WATCHDOG,		"hcall-watchdog"},
 };
 
 /* Build up the firmware features bitmask using the contents of
-- 
2.27.0

[PATCH v3 3/4] powerpc/pseries: register pseries-wdt device with platform bus

[Scott Cheloha]

PAPR v2.12 defines a new hypercall, H_WATCHDOG.  The hypercall permits
guest control of one or more virtual watchdog timers.

These timers do not conform to PowerPC device conventions.  They are
not affixed to any extant bus, nor do they have full representation in
the device tree.

As a workaround we represent them as platform devices.

This patch registers a single platform device, "pseries-wdt", with the
platform bus if the FW_FEATURE_WATCHDOG flag is set.

A driver for this device, "pseries-wdt", will be introduced in a
subsequent patch.

Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
---
 arch/powerpc/platforms/pseries/setup.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index ee4f1db49515..dd9d3f500cff 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -14,6 +14,7 @@
 
 #include <linux/cpu.h>
 #include <linux/errno.h>
+#include <linux/platform_device.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
@@ -169,6 +170,18 @@ static void __init fwnmi_init(void)
 #endif
 }
 
+/*
+ * Affix a device for the first timer to the platform bus if
+ * we have firmware support for the H_WATCHDOG hypercall.
+ */
+static __init int pseries_wdt_init(void)
+{
+	if (firmware_has_feature(FW_FEATURE_WATCHDOG))
+		platform_device_register_simple("pseries-wdt", 0, NULL, 0);
+	return 0;
+}
+machine_subsys_initcall(pseries, pseries_wdt_init);
+
 static void pseries_8259_cascade(struct irq_desc *desc)
 {
 	struct irq_chip *chip = irq_desc_get_chip(desc);
-- 
2.27.0

[PATCH v3 4/4] watchdog/pseries-wdt: initial support for H_WATCHDOG-based watchdog timers

[Scott Cheloha]

PAPR v2.12 defines a new hypercall, H_WATCHDOG.  The hypercall permits
guest control of one or more virtual watchdog timers.  The timers have
millisecond granularity.  The guest is terminated when a timer
expires.

This patch adds a watchdog driver for these timers, "pseries-wdt".

pseries_wdt_probe() currently assumes the existence of only one
platform device and always assigns it watchdogNumber 1.  If we ever
expose more than one timer to userspace we will need to devise a way
to assign a distinct watchdogNumber to each platform device at device
registration time.

Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
---
 .../watchdog/watchdog-parameters.rst          |  12 +
 drivers/watchdog/Kconfig                      |   8 +
 drivers/watchdog/Makefile                     |   1 +
 drivers/watchdog/pseries-wdt.c                | 239 ++++++++++++++++++
 4 files changed, 260 insertions(+)
 create mode 100644 drivers/watchdog/pseries-wdt.c

diff --git a/Documentation/watchdog/watchdog-parameters.rst b/Documentation/watchdog/watchdog-parameters.rst
index 223c99361a30..29153eed6689 100644
--- a/Documentation/watchdog/watchdog-parameters.rst
+++ b/Documentation/watchdog/watchdog-parameters.rst
@@ -425,6 +425,18 @@ pnx833x_wdt:
 
 -------------------------------------------------
 
+pseries-wdt:
+    action:
+	Action taken when watchdog expires: 0 (power off), 1 (restart),
+	2 (dump and restart). (default=1)
+    timeout:
+	Initial watchdog timeout in seconds. (default=60)
+    nowayout:
+	Watchdog cannot be stopped once started.
+	(default=kernel config parameter)
+
+-------------------------------------------------
+
 rc32434_wdt:
     timeout:
 	Watchdog timeout value, in seconds (default=20)
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 32fd37698932..a2429604a4ab 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -1962,6 +1962,14 @@ config MEN_A21_WDT
 
 # PPC64 Architecture
 
+config PSERIES_WDT
+	tristate "POWER Architecture Platform Watchdog Timer"
+	depends on PPC_PSERIES
+	select WATCHDOG_CORE
+	help
+	  Driver for virtual watchdog timers provided by PAPR
+	  hypervisors (e.g. PowerVM, KVM).
+
 config WATCHDOG_RTAS
 	tristate "RTAS watchdog"
 	depends on PPC_RTAS
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index c324e9d820e9..cdeb119e6e61 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -187,6 +187,7 @@ obj-$(CONFIG_BOOKE_WDT) += booke_wdt.o
 obj-$(CONFIG_MEN_A21_WDT) += mena21_wdt.o
 
 # PPC64 Architecture
+obj-$(CONFIG_PSERIES_WDT) += pseries-wdt.o
 obj-$(CONFIG_WATCHDOG_RTAS) += wdrtas.o
 
 # S390 Architecture
diff --git a/drivers/watchdog/pseries-wdt.c b/drivers/watchdog/pseries-wdt.c
new file mode 100644
index 000000000000..7f53b5293409
--- /dev/null
+++ b/drivers/watchdog/pseries-wdt.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2022 International Business Machines, Inc.
+ */
+
+#include <linux/bitops.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/math.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/platform_device.h>
+#include <linux/time64.h>
+#include <linux/watchdog.h>
+
+#define DRV_NAME "pseries-wdt"
+
+/*
+ * H_WATCHDOG Input
+ *
+ * R4: "flags":
+ *
+ *         Bits 48-55: "operation"
+ */
+#define PSERIES_WDTF_OP_START	0x100UL		/* start timer */
+#define PSERIES_WDTF_OP_STOP	0x200UL		/* stop timer */
+#define PSERIES_WDTF_OP_QUERY	0x300UL		/* query timer capabilities */
+
+/*
+ *         Bits 56-63: "timeoutAction" (for "Start Watchdog" only)
+ */
+#define PSERIES_WDTF_ACTION_HARD_POWEROFF	0x1UL	/* poweroff */
+#define PSERIES_WDTF_ACTION_HARD_RESTART	0x2UL	/* restart */
+#define PSERIES_WDTF_ACTION_DUMP_RESTART	0x3UL	/* dump + restart */
+
+/*
+ * H_WATCHDOG Output
+ *
+ * R3: Return code
+ *
+ *     H_SUCCESS    The operation completed.
+ *
+ *     H_BUSY	    The hypervisor is too busy; retry the operation.
+ *
+ *     H_PARAMETER  The given "flags" are somehow invalid.  Either the
+ *                  "operation" or "timeoutAction" is invalid, or a
+ *                  reserved bit is set.
+ *
+ *     H_P2         The given "watchdogNumber" is zero or exceeds the
+ *                  supported maximum value.
+ *
+ *     H_P3         The given "timeoutInMs" is below the supported
+ *                  minimum value.
+ *
+ *     H_NOOP       The given "watchdogNumber" is already stopped.
+ *
+ *     H_HARDWARE   The operation failed for ineffable reasons.
+ *
+ *     H_FUNCTION   The H_WATCHDOG hypercall is not supported by this
+ *                  hypervisor.
+ *
+ * R4:
+ *
+ * - For the "Query Watchdog Capabilities" operation, a 64-bit
+ *   structure:
+ */
+#define PSERIES_WDTQ_MIN_TIMEOUT(cap)	(((cap) >> 48) & 0xffff)
+#define PSERIES_WDTQ_MAX_NUMBER(cap)	(((cap) >> 32) & 0xffff)
+
+static const unsigned long pseries_wdt_action[] = {
+	[0] = PSERIES_WDTF_ACTION_HARD_POWEROFF,
+	[1] = PSERIES_WDTF_ACTION_HARD_RESTART,
+	[2] = PSERIES_WDTF_ACTION_DUMP_RESTART,
+};
+
+#define WATCHDOG_ACTION 1
+static unsigned int action = WATCHDOG_ACTION;
+module_param(action, uint, 0444);
+MODULE_PARM_DESC(action, "Action taken when watchdog expires (default="
+		 __MODULE_STRING(WATCHDOG_ACTION) ")");
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0444);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
+		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+#define WATCHDOG_TIMEOUT 60
+static unsigned int timeout = WATCHDOG_TIMEOUT;
+module_param(timeout, uint, 0444);
+MODULE_PARM_DESC(timeout, "Initial watchdog timeout in seconds (default="
+		 __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
+
+struct pseries_wdt {
+	struct watchdog_device wd;
+	unsigned long action;
+	unsigned long num;		/* Watchdog numbers are 1-based */
+};
+
+static int pseries_wdt_start(struct watchdog_device *wdd)
+{
+	struct pseries_wdt *pw = watchdog_get_drvdata(wdd);
+	struct device *dev = wdd->parent;
+	unsigned long flags, msecs;
+	long rc;
+
+	flags = pw->action | PSERIES_WDTF_OP_START;
+	msecs = wdd->timeout * MSEC_PER_SEC;
+	rc = plpar_hcall_norets(H_WATCHDOG, flags, pw->num, msecs);
+	if (rc != H_SUCCESS) {
+		dev_crit(dev, "H_WATCHDOG: %ld: failed to start timer %lu",
+			 rc, pw->num);
+		return -EIO;
+	}
+	return 0;
+}
+
+static int pseries_wdt_stop(struct watchdog_device *wdd)
+{
+	struct pseries_wdt *pw = watchdog_get_drvdata(wdd);
+	struct device *dev = wdd->parent;
+	long rc;
+
+	rc = plpar_hcall_norets(H_WATCHDOG, PSERIES_WDTF_OP_STOP, pw->num);
+	if (rc != H_SUCCESS && rc != H_NOOP) {
+		dev_crit(dev, "H_WATCHDOG: %ld: failed to stop timer %lu",
+			 rc, pw->num);
+		return -EIO;
+	}
+	return 0;
+}
+
+static struct watchdog_info pseries_wdt_info = {
+	.identity = DRV_NAME,
+	.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT
+	    | WDIOF_PRETIMEOUT,
+};
+
+static const struct watchdog_ops pseries_wdt_ops = {
+	.owner = THIS_MODULE,
+	.start = pseries_wdt_start,
+	.stop = pseries_wdt_stop,
+};
+
+static int pseries_wdt_probe(struct platform_device *pdev)
+{
+	unsigned long ret[PLPAR_HCALL_BUFSIZE] = { 0 };
+	struct pseries_wdt *pw;
+	unsigned long cap;
+	long msecs, rc;
+	int err;
+
+	rc = plpar_hcall(H_WATCHDOG, ret, PSERIES_WDTF_OP_QUERY);
+	if (rc == H_FUNCTION)
+		return -ENODEV;
+	if (rc != H_SUCCESS)
+		return -EIO;
+	cap = ret[0];
+
+	pw = devm_kzalloc(&pdev->dev, sizeof(*pw), GFP_KERNEL);
+	if (!pw)
+		return -ENOMEM;
+
+	/*
+	 * Assume watchdogNumber 1 for now.  If we ever support
+	 * multiple timers we will need to devise a way to choose a
+	 * distinct watchdogNumber for each platform device at device
+	 * registration time.
+	 */
+	pw->num = 1;
+	if (PSERIES_WDTQ_MAX_NUMBER(cap) < pw->num)
+		return -ENODEV;
+
+	if (action >= ARRAY_SIZE(pseries_wdt_action))
+		return -EINVAL;
+	pw->action = pseries_wdt_action[action];
+
+	pw->wd.parent = &pdev->dev;
+	pw->wd.info = &pseries_wdt_info;
+	pw->wd.ops = &pseries_wdt_ops;
+	msecs = PSERIES_WDTQ_MIN_TIMEOUT(cap);
+	pw->wd.min_timeout = DIV_ROUND_UP(msecs, MSEC_PER_SEC);
+	pw->wd.max_timeout = UINT_MAX / 1000;	/* from linux/watchdog.h */
+	pw->wd.timeout = timeout;
+	if (watchdog_init_timeout(&pw->wd, 0, NULL))
+		return -EINVAL;
+	watchdog_set_nowayout(&pw->wd, nowayout);
+	watchdog_stop_on_reboot(&pw->wd);
+	watchdog_stop_on_unregister(&pw->wd);
+	watchdog_set_drvdata(&pw->wd, pw);
+
+	err = devm_watchdog_register_device(&pdev->dev, &pw->wd);
+	if (err)
+		return err;
+
+	platform_set_drvdata(pdev, &pw->wd);
+
+	return 0;
+}
+
+static int pseries_wdt_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct watchdog_device *wd = platform_get_drvdata(pdev);
+
+	if (watchdog_active(wd))
+		return pseries_wdt_stop(wd);
+	return 0;
+}
+
+static int pseries_wdt_resume(struct platform_device *pdev)
+{
+	struct watchdog_device *wd = platform_get_drvdata(pdev);
+
+	if (watchdog_active(wd))
+		return pseries_wdt_start(wd);
+	return 0;
+}
+
+static const struct platform_device_id pseries_wdt_id[] = {
+	{ .name = "pseries-wdt" },
+	{}
+};
+MODULE_DEVICE_TABLE(platform, pseries_wdt_id);
+
+static struct platform_driver pseries_wdt_driver = {
+	.driver = {
+		.name = DRV_NAME,
+	},
+	.id_table = pseries_wdt_id,
+	.probe = pseries_wdt_probe,
+	.resume = pseries_wdt_resume,
+	.suspend = pseries_wdt_suspend,
+};
+module_platform_driver(pseries_wdt_driver);
+
+MODULE_AUTHOR("Alexey Kardashevskiy");
+MODULE_AUTHOR("Scott Cheloha");
+MODULE_DESCRIPTION("POWER Architecture Platform Watchdog Driver");
+MODULE_LICENSE("GPL");
-- 
2.27.0

Re: [PATCH v3 4/4] watchdog/pseries-wdt: initial support for H_WATCHDOG-based watchdog timers

[Guenter Roeck]

On 7/13/22 13:23, Scott Cheloha wrote:
> PAPR v2.12 defines a new hypercall, H_WATCHDOG.  The hypercall permits
> guest control of one or more virtual watchdog timers.  The timers have
> millisecond granularity.  The guest is terminated when a timer
> expires.
> 
> This patch adds a watchdog driver for these timers, "pseries-wdt".
> 
> pseries_wdt_probe() currently assumes the existence of only one
> platform device and always assigns it watchdogNumber 1.  If we ever
> expose more than one timer to userspace we will need to devise a way
> to assign a distinct watchdogNumber to each platform device at device
> registration time.
> 
> Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>

Acked-by: Guenter Roeck <linux@roeck-us.net>

> ---
>   .../watchdog/watchdog-parameters.rst          |  12 +
>   drivers/watchdog/Kconfig                      |   8 +
>   drivers/watchdog/Makefile                     |   1 +
>   drivers/watchdog/pseries-wdt.c                | 239 ++++++++++++++++++
>   4 files changed, 260 insertions(+)
>   create mode 100644 drivers/watchdog/pseries-wdt.c
> 
> diff --git a/Documentation/watchdog/watchdog-parameters.rst b/Documentation/watchdog/watchdog-parameters.rst
> index 223c99361a30..29153eed6689 100644
> --- a/Documentation/watchdog/watchdog-parameters.rst
> +++ b/Documentation/watchdog/watchdog-parameters.rst
> @@ -425,6 +425,18 @@ pnx833x_wdt:
>   
>   -------------------------------------------------
>   
> +pseries-wdt:
> +    action:
> +	Action taken when watchdog expires: 0 (power off), 1 (restart),
> +	2 (dump and restart). (default=1)
> +    timeout:
> +	Initial watchdog timeout in seconds. (default=60)
> +    nowayout:
> +	Watchdog cannot be stopped once started.
> +	(default=kernel config parameter)
> +
> +-------------------------------------------------
> +
>   rc32434_wdt:
>       timeout:
>   	Watchdog timeout value, in seconds (default=20)
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 32fd37698932..a2429604a4ab 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1962,6 +1962,14 @@ config MEN_A21_WDT
>   
>   # PPC64 Architecture
>   
> +config PSERIES_WDT
> +	tristate "POWER Architecture Platform Watchdog Timer"
> +	depends on PPC_PSERIES
> +	select WATCHDOG_CORE
> +	help
> +	  Driver for virtual watchdog timers provided by PAPR
> +	  hypervisors (e.g. PowerVM, KVM).
> +
>   config WATCHDOG_RTAS
>   	tristate "RTAS watchdog"
>   	depends on PPC_RTAS
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index c324e9d820e9..cdeb119e6e61 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -187,6 +187,7 @@ obj-$(CONFIG_BOOKE_WDT) += booke_wdt.o
>   obj-$(CONFIG_MEN_A21_WDT) += mena21_wdt.o
>   
>   # PPC64 Architecture
> +obj-$(CONFIG_PSERIES_WDT) += pseries-wdt.o
>   obj-$(CONFIG_WATCHDOG_RTAS) += wdrtas.o
>   
>   # S390 Architecture
> diff --git a/drivers/watchdog/pseries-wdt.c b/drivers/watchdog/pseries-wdt.c
> new file mode 100644
> index 000000000000..7f53b5293409
> --- /dev/null
> +++ b/drivers/watchdog/pseries-wdt.c
> @@ -0,0 +1,239 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (c) 2022 International Business Machines, Inc.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/kernel.h>
> +#include <linux/limits.h>
> +#include <linux/math.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/platform_device.h>
> +#include <linux/time64.h>
> +#include <linux/watchdog.h>
> +
> +#define DRV_NAME "pseries-wdt"
> +
> +/*
> + * H_WATCHDOG Input
> + *
> + * R4: "flags":
> + *
> + *         Bits 48-55: "operation"
> + */
> +#define PSERIES_WDTF_OP_START	0x100UL		/* start timer */
> +#define PSERIES_WDTF_OP_STOP	0x200UL		/* stop timer */
> +#define PSERIES_WDTF_OP_QUERY	0x300UL		/* query timer capabilities */
> +
> +/*
> + *         Bits 56-63: "timeoutAction" (for "Start Watchdog" only)
> + */
> +#define PSERIES_WDTF_ACTION_HARD_POWEROFF	0x1UL	/* poweroff */
> +#define PSERIES_WDTF_ACTION_HARD_RESTART	0x2UL	/* restart */
> +#define PSERIES_WDTF_ACTION_DUMP_RESTART	0x3UL	/* dump + restart */
> +
> +/*
> + * H_WATCHDOG Output
> + *
> + * R3: Return code
> + *
> + *     H_SUCCESS    The operation completed.
> + *
> + *     H_BUSY	    The hypervisor is too busy; retry the operation.
> + *
> + *     H_PARAMETER  The given "flags" are somehow invalid.  Either the
> + *                  "operation" or "timeoutAction" is invalid, or a
> + *                  reserved bit is set.
> + *
> + *     H_P2         The given "watchdogNumber" is zero or exceeds the
> + *                  supported maximum value.
> + *
> + *     H_P3         The given "timeoutInMs" is below the supported
> + *                  minimum value.
> + *
> + *     H_NOOP       The given "watchdogNumber" is already stopped.
> + *
> + *     H_HARDWARE   The operation failed for ineffable reasons.
> + *
> + *     H_FUNCTION   The H_WATCHDOG hypercall is not supported by this
> + *                  hypervisor.
> + *
> + * R4:
> + *
> + * - For the "Query Watchdog Capabilities" operation, a 64-bit
> + *   structure:
> + */
> +#define PSERIES_WDTQ_MIN_TIMEOUT(cap)	(((cap) >> 48) & 0xffff)
> +#define PSERIES_WDTQ_MAX_NUMBER(cap)	(((cap) >> 32) & 0xffff)
> +
> +static const unsigned long pseries_wdt_action[] = {
> +	[0] = PSERIES_WDTF_ACTION_HARD_POWEROFF,
> +	[1] = PSERIES_WDTF_ACTION_HARD_RESTART,
> +	[2] = PSERIES_WDTF_ACTION_DUMP_RESTART,
> +};
> +
> +#define WATCHDOG_ACTION 1
> +static unsigned int action = WATCHDOG_ACTION;
> +module_param(action, uint, 0444);
> +MODULE_PARM_DESC(action, "Action taken when watchdog expires (default="
> +		 __MODULE_STRING(WATCHDOG_ACTION) ")");
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +module_param(nowayout, bool, 0444);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> +		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +#define WATCHDOG_TIMEOUT 60
> +static unsigned int timeout = WATCHDOG_TIMEOUT;
> +module_param(timeout, uint, 0444);
> +MODULE_PARM_DESC(timeout, "Initial watchdog timeout in seconds (default="
> +		 __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
> +
> +struct pseries_wdt {
> +	struct watchdog_device wd;
> +	unsigned long action;
> +	unsigned long num;		/* Watchdog numbers are 1-based */
> +};
> +
> +static int pseries_wdt_start(struct watchdog_device *wdd)
> +{
> +	struct pseries_wdt *pw = watchdog_get_drvdata(wdd);
> +	struct device *dev = wdd->parent;
> +	unsigned long flags, msecs;
> +	long rc;
> +
> +	flags = pw->action | PSERIES_WDTF_OP_START;
> +	msecs = wdd->timeout * MSEC_PER_SEC;
> +	rc = plpar_hcall_norets(H_WATCHDOG, flags, pw->num, msecs);
> +	if (rc != H_SUCCESS) {
> +		dev_crit(dev, "H_WATCHDOG: %ld: failed to start timer %lu",
> +			 rc, pw->num);
> +		return -EIO;
> +	}
> +	return 0;
> +}
> +
> +static int pseries_wdt_stop(struct watchdog_device *wdd)
> +{
> +	struct pseries_wdt *pw = watchdog_get_drvdata(wdd);
> +	struct device *dev = wdd->parent;
> +	long rc;
> +
> +	rc = plpar_hcall_norets(H_WATCHDOG, PSERIES_WDTF_OP_STOP, pw->num);
> +	if (rc != H_SUCCESS && rc != H_NOOP) {
> +		dev_crit(dev, "H_WATCHDOG: %ld: failed to stop timer %lu",
> +			 rc, pw->num);
> +		return -EIO;
> +	}
> +	return 0;
> +}
> +
> +static struct watchdog_info pseries_wdt_info = {
> +	.identity = DRV_NAME,
> +	.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE | WDIOF_SETTIMEOUT
> +	    | WDIOF_PRETIMEOUT,
> +};
> +
> +static const struct watchdog_ops pseries_wdt_ops = {
> +	.owner = THIS_MODULE,
> +	.start = pseries_wdt_start,
> +	.stop = pseries_wdt_stop,
> +};
> +
> +static int pseries_wdt_probe(struct platform_device *pdev)
> +{
> +	unsigned long ret[PLPAR_HCALL_BUFSIZE] = { 0 };
> +	struct pseries_wdt *pw;
> +	unsigned long cap;
> +	long msecs, rc;
> +	int err;
> +
> +	rc = plpar_hcall(H_WATCHDOG, ret, PSERIES_WDTF_OP_QUERY);
> +	if (rc == H_FUNCTION)
> +		return -ENODEV;
> +	if (rc != H_SUCCESS)
> +		return -EIO;
> +	cap = ret[0];
> +
> +	pw = devm_kzalloc(&pdev->dev, sizeof(*pw), GFP_KERNEL);
> +	if (!pw)
> +		return -ENOMEM;
> +
> +	/*
> +	 * Assume watchdogNumber 1 for now.  If we ever support
> +	 * multiple timers we will need to devise a way to choose a
> +	 * distinct watchdogNumber for each platform device at device
> +	 * registration time.
> +	 */
> +	pw->num = 1;
> +	if (PSERIES_WDTQ_MAX_NUMBER(cap) < pw->num)
> +		return -ENODEV;
> +
> +	if (action >= ARRAY_SIZE(pseries_wdt_action))
> +		return -EINVAL;
> +	pw->action = pseries_wdt_action[action];
> +
> +	pw->wd.parent = &pdev->dev;
> +	pw->wd.info = &pseries_wdt_info;
> +	pw->wd.ops = &pseries_wdt_ops;
> +	msecs = PSERIES_WDTQ_MIN_TIMEOUT(cap);
> +	pw->wd.min_timeout = DIV_ROUND_UP(msecs, MSEC_PER_SEC);
> +	pw->wd.max_timeout = UINT_MAX / 1000;	/* from linux/watchdog.h */
> +	pw->wd.timeout = timeout;
> +	if (watchdog_init_timeout(&pw->wd, 0, NULL))
> +		return -EINVAL;
> +	watchdog_set_nowayout(&pw->wd, nowayout);
> +	watchdog_stop_on_reboot(&pw->wd);
> +	watchdog_stop_on_unregister(&pw->wd);
> +	watchdog_set_drvdata(&pw->wd, pw);
> +
> +	err = devm_watchdog_register_device(&pdev->dev, &pw->wd);
> +	if (err)
> +		return err;
> +
> +	platform_set_drvdata(pdev, &pw->wd);
> +
> +	return 0;
> +}
> +
> +static int pseries_wdt_suspend(struct platform_device *pdev, pm_message_t state)
> +{
> +	struct watchdog_device *wd = platform_get_drvdata(pdev);
> +
> +	if (watchdog_active(wd))
> +		return pseries_wdt_stop(wd);
> +	return 0;
> +}
> +
> +static int pseries_wdt_resume(struct platform_device *pdev)
> +{
> +	struct watchdog_device *wd = platform_get_drvdata(pdev);
> +
> +	if (watchdog_active(wd))
> +		return pseries_wdt_start(wd);
> +	return 0;
> +}
> +
> +static const struct platform_device_id pseries_wdt_id[] = {
> +	{ .name = "pseries-wdt" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(platform, pseries_wdt_id);
> +
> +static struct platform_driver pseries_wdt_driver = {
> +	.driver = {
> +		.name = DRV_NAME,
> +	},
> +	.id_table = pseries_wdt_id,
> +	.probe = pseries_wdt_probe,
> +	.resume = pseries_wdt_resume,
> +	.suspend = pseries_wdt_suspend,
> +};
> +module_platform_driver(pseries_wdt_driver);
> +
> +MODULE_AUTHOR("Alexey Kardashevskiy");
> +MODULE_AUTHOR("Scott Cheloha");
> +MODULE_DESCRIPTION("POWER Architecture Platform Watchdog Driver");
> +MODULE_LICENSE("GPL");

Re: [PATCH v3 4/4] watchdog/pseries-wdt: initial support for H_WATCHDOG-based watchdog timers

[Scott Cheloha]

On Wed, Jul 13, 2022 at 01:50:14PM -0700, Guenter Roeck wrote:
> On 7/13/22 13:23, Scott Cheloha wrote:
> > PAPR v2.12 defines a new hypercall, H_WATCHDOG.  The hypercall permits
> > guest control of one or more virtual watchdog timers.  The timers have
> > millisecond granularity.  The guest is terminated when a timer
> > expires.
> > 
> > This patch adds a watchdog driver for these timers, "pseries-wdt".
> > 
> > pseries_wdt_probe() currently assumes the existence of only one
> > platform device and always assigns it watchdogNumber 1.  If we ever
> > expose more than one timer to userspace we will need to devise a way
> > to assign a distinct watchdogNumber to each platform device at device
> > registration time.
> > 
> > Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
> 
> Acked-by: Guenter Roeck <linux@roeck-us.net>

Guenter, Michael,

Which tree is taking this series?

watchdog-next or PPC development?

-Scott

Re: [PATCH v3 4/4] watchdog/pseries-wdt: initial support for H_WATCHDOG-based watchdog timers

[Guenter Roeck]

On Mon, Jul 25, 2022 at 11:11:41AM -0500, Scott Cheloha wrote:
> On Wed, Jul 13, 2022 at 01:50:14PM -0700, Guenter Roeck wrote:
> > On 7/13/22 13:23, Scott Cheloha wrote:
> > > PAPR v2.12 defines a new hypercall, H_WATCHDOG.  The hypercall permits
> > > guest control of one or more virtual watchdog timers.  The timers have
> > > millisecond granularity.  The guest is terminated when a timer
> > > expires.
> > > 
> > > This patch adds a watchdog driver for these timers, "pseries-wdt".
> > > 
> > > pseries_wdt_probe() currently assumes the existence of only one
> > > platform device and always assigns it watchdogNumber 1.  If we ever
> > > expose more than one timer to userspace we will need to devise a way
> > > to assign a distinct watchdogNumber to each platform device at device
> > > registration time.
> > > 
> > > Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
> > 
> > Acked-by: Guenter Roeck <linux@roeck-us.net>
> 
> Guenter, Michael,
> 
> Which tree is taking this series?
> 
The series includes non-watchdog changes, so my expectation was that some
other tree would take it.

Guenter

> watchdog-next or PPC development?
> 
> -Scott

Re: [PATCH v3 4/4] watchdog/pseries-wdt: initial support for H_WATCHDOG-based watchdog timers

[Michael Ellerman]

Guenter Roeck <linux@roeck-us.net> writes:
> On Mon, Jul 25, 2022 at 11:11:41AM -0500, Scott Cheloha wrote:
>> On Wed, Jul 13, 2022 at 01:50:14PM -0700, Guenter Roeck wrote:
>> > On 7/13/22 13:23, Scott Cheloha wrote:
>> > > PAPR v2.12 defines a new hypercall, H_WATCHDOG.  The hypercall permits
>> > > guest control of one or more virtual watchdog timers.  The timers have
>> > > millisecond granularity.  The guest is terminated when a timer
>> > > expires.
>> > > 
>> > > This patch adds a watchdog driver for these timers, "pseries-wdt".
>> > > 
>> > > pseries_wdt_probe() currently assumes the existence of only one
>> > > platform device and always assigns it watchdogNumber 1.  If we ever
>> > > expose more than one timer to userspace we will need to devise a way
>> > > to assign a distinct watchdogNumber to each platform device at device
>> > > registration time.
>> > > 
>> > > Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com>
>> > 
>> > Acked-by: Guenter Roeck <linux@roeck-us.net>
>> 
>> Guenter, Michael,
>> 
>> Which tree is taking this series?

powerpc.

It's been in next-test/next for about a week.

It's in linux-next today.

> The series includes non-watchdog changes, so my expectation was that some
> other tree would take it.

Yep, thanks for the ack.

cheers

Re: [PATCH v3 0/4] pseries-wdt: initial support for H_WATCHDOG-based watchdog timers

[Michael Ellerman]

On Wed, 13 Jul 2022 15:23:31 -0500, Scott Cheloha wrote:
> PAPR v2.12 defines a new hypercall, H_WATCHDOG.  This patch series
> adds support for this hypercall to powerpc/pseries kernels and
> introduces a new watchdog driver, "pseries-wdt", for the virtual
> timers exposed by the hypercall.
> 
> This series is preceded by the following:
> 
> [...]

Applied to powerpc/next.

[1/4] powerpc/pseries: hvcall.h: add H_WATCHDOG opcode, H_NOOP return code
      https://git.kernel.org/powerpc/c/c6b2bd262b33aa2451f52aec2190131d1762945a
[2/4] powerpc/pseries: add FW_FEATURE_WATCHDOG flag
      https://git.kernel.org/powerpc/c/1621563ec62ff143c7b817dd5eab0884cdfaf89d
[3/4] powerpc/pseries: register pseries-wdt device with platform bus
      https://git.kernel.org/powerpc/c/578030bfe117060bf86c81aaa7b3faead4589810
[4/4] watchdog/pseries-wdt: initial support for H_WATCHDOG-based watchdog timers
      https://git.kernel.org/powerpc/c/69472ffa6575e3a1c1e3324dd06395af0f63eb71

cheers