greybus: svc_watchdog: Add sysfs file to change the behavior of bite

Currently, AP performs unipro_reset if SVC fails to response to its
ping. While this error recovery is best suited for the end-user
experience, errors in the UniPro network could potentially go unnoticed
by the QA and fishfooders in the development phase of the project. This
patch adds an option to trigger a kernel panic so logs can be collected
for analysis.

Testing Done:
 - Reproduce issue and observe kernel panic when
   watchdob_control is changed to 'panic'

Signed-off-by: David Lin <dtwlin@google.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/drivers/staging/greybus/Documentation/sysfs-bus-greybus b/drivers/staging/greybus/Documentation/sysfs-bus-greybus
index e202eac1f0015fa3786573c91872d2d7002caf61..c49c81b133bc690504f93b252e48faa45a63dd03 100644 (file)
--- a/drivers/staging/greybus/Documentation/sysfs-bus-greybus
+++ b/drivers/staging/greybus/Documentation/sysfs-bus-greybus
@@ -257,3 +257,19 @@ Contact:   Greg Kroah-Hartman <greg@kroah.com>
 Description:
                If the SVC watchdog is enabled or not.  Writing 0 to this
                file will disable the watchdog, writing 1 will enable it.
+
+What:          /sys/bus/greybus/devices/N-svc/watchdog_action
+Date:          July 2016
+KernelVersion: 4.XX
+Contact:       Greg Kroah-Hartman <greg@kroah.com>
+Description:
+               This attribute indicates the action to be performed upon SVC
+               watchdog bite.
+
+               The action can be one of the "reset" or "panic". Writing either
+               one of the "reset" or "panic" will change the behavior of SVC
+               watchdog bite. Default value is "reset".
+
+               "reset" means the UniPro subsystem is to be reset.
+
+               "panic" means SVC watchdog bite will cause kernel to panic.

diff --git a/drivers/staging/greybus/svc.c b/drivers/staging/greybus/svc.c
index da9bb1f182f72fee943d0cbd1dc969c522ec6e1c..1170515a2a4e6be25c47040eb717baa28c9bc04c 100644 (file)
--- a/drivers/staging/greybus/svc.c
+++ b/drivers/staging/greybus/svc.c
@@ -100,6 +100,36 @@ static ssize_t watchdog_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(watchdog);
 
+static ssize_t watchdog_action_show(struct device *dev,
+                                   struct device_attribute *attr, char *buf)
+{
+       struct gb_svc *svc = to_gb_svc(dev);
+
+       if (svc->action == GB_SVC_WATCHDOG_BITE_PANIC_KERNEL)
+               return sprintf(buf, "panic\n");
+       else if (svc->action == GB_SVC_WATCHDOG_BITE_RESET_UNIPRO)
+               return sprintf(buf, "reset\n");
+
+       return -EINVAL;
+}
+
+static ssize_t watchdog_action_store(struct device *dev,
+                                    struct device_attribute *attr,
+                                    const char *buf, size_t len)
+{
+       struct gb_svc *svc = to_gb_svc(dev);
+
+       if (sysfs_streq(buf, "panic"))
+               svc->action = GB_SVC_WATCHDOG_BITE_PANIC_KERNEL;
+       else if (sysfs_streq(buf, "reset"))
+               svc->action = GB_SVC_WATCHDOG_BITE_RESET_UNIPRO;
+       else
+               return -EINVAL;
+
+       return len;
+}
+static DEVICE_ATTR_RW(watchdog_action);
+
 static int gb_svc_pwrmon_rail_count_get(struct gb_svc *svc, u8 *value)
 {
        struct gb_svc_pwrmon_rail_count_get_response response;
@@ -222,6 +252,7 @@ static struct attribute *svc_attrs[] = {
        &dev_attr_ap_intf_id.attr,
        &dev_attr_intf_eject.attr,
        &dev_attr_watchdog.attr,
+       &dev_attr_watchdog_action.attr,
        NULL,
 };
 ATTRIBUTE_GROUPS(svc);

diff --git a/drivers/staging/greybus/svc.h b/drivers/staging/greybus/svc.h
index f632790a54f485afe474d1253984ba8ebd978450..d1d7ef967385201f7dbdcfcf9f95c3fca6d2ce92 100644 (file)
--- a/drivers/staging/greybus/svc.h
+++ b/drivers/staging/greybus/svc.h
@@ -20,6 +20,11 @@ enum gb_svc_state {
        GB_SVC_STATE_SVC_HELLO,
 };
 
+enum gb_svc_watchdog_bite {
+       GB_SVC_WATCHDOG_BITE_RESET_UNIPRO = 0,
+       GB_SVC_WATCHDOG_BITE_PANIC_KERNEL,
+};
+
 struct gb_svc_watchdog;
 
 struct svc_debugfs_pwrmon_rail {
@@ -43,6 +48,7 @@ struct gb_svc {
        u8 protocol_minor;
 
        struct gb_svc_watchdog  *watchdog;
+       enum gb_svc_watchdog_bite action;
 
        struct dentry *debugfs_dentry;
        struct svc_debugfs_pwrmon_rail *pwrmon_rails;

diff --git a/drivers/staging/greybus/svc_watchdog.c b/drivers/staging/greybus/svc_watchdog.c
index 6cd3bac59852ebe63d25a9e5fc339bff65de71b3..1295cc153af928601b854494814dfbb1b80ee292 100644 (file)
--- a/drivers/staging/greybus/svc_watchdog.c
+++ b/drivers/staging/greybus/svc_watchdog.c
@@ -83,16 +83,21 @@ static void do_work(struct work_struct *work)
                dev_err(&svc->dev,
                        "SVC ping has returned %d, something is wrong!!!\n",
                        retval);
-               dev_err(&svc->dev, "Resetting the greybus network, watch out!!!\n");
 
-               INIT_DELAYED_WORK(&reset_work, greybus_reset);
-               queue_delayed_work(system_wq, &reset_work, HZ/2);
+               if (svc->action == GB_SVC_WATCHDOG_BITE_PANIC_KERNEL) {
+                       panic("SVC is not responding\n");
+               } else if (svc->action == GB_SVC_WATCHDOG_BITE_RESET_UNIPRO) {
+                       dev_err(&svc->dev, "Resetting the greybus network, watch out!!!\n");
 
-               /*
-                * Disable ourselves, we don't want to trip again unless
-                * userspace wants us to.
-                */
-               watchdog->enabled = false;
+                       INIT_DELAYED_WORK(&reset_work, greybus_reset);
+                       queue_delayed_work(system_wq, &reset_work, HZ / 2);
+
+                       /*
+                        * Disable ourselves, we don't want to trip again unless
+                        * userspace wants us to.
+                        */
+                       watchdog->enabled = false;
+               }
        }
 
        /* resubmit our work to happen again, if we are still "alive" */