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 <chel...@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

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