Watchdog

Overview

In the Hardware Driver Foundation (HDF), the Watchdog (also called Watchdog timer) module uses the independent service mode for API adaptation. In this mode, each device independently publishes a device service to handle external access requests. After receiving an access request from an API, the device manager extracts the parameters in the request to call the internal method of the target device. In the independent service mode, the service management capabilities of the HDF Device Manager can be directly used. However, you need to configure a device node for each device, which increases the memory usage.

Figure 1 Independent service mode

Available APIs

WatchdogMethod

struct WatchdogMethod {
  int32_t (*getStatus)(struct WatchdogCntlr *wdt, int32_t *status);
  int32_t (*setTimeout)(struct WatchdogCntlr *wdt, uint32_t seconds);
  int32_t (*getTimeout)(struct WatchdogCntlr *wdt, uint32_t *seconds);
  int32_t (*start)(struct WatchdogCntlr *wdt);
  int32_t (*stop)(struct WatchdogCntlr *wdt);
  int32_t (*feed)(struct WatchdogCntlr *wdt);
  int32_t (*getPriv)(struct WatchdogCntlr *wdt); // (Optional) If WatchdogCntlr has the priv member, instantiate priv.
  void (*releasePriv)(struct WatchdogCntlr *wdt);// (Optional)
};

Table 1 Callbacks for the members in the WatchdogMethod structure

Callback	Input Parameter	Output Parameter	Return Value	Description
getStatus	wdt: structure pointer to the Watchdog controller at the core layer.	status: int32_t pointer indicating the watchdog status (started or stopped).	HDF_STATUS	Obtains the watchdog status.
start	wdt: structure pointer to the Watchdog controller at the core layer.	–	HDF_STATUS	Starts a watchdog.
stop	wdt: structure pointer to the Watchdog controller at the core layer.	–	HDF_STATUS	Stops a watchdog.
setTimeout	wdt: structure pointer to the Watchdog controller at the core layer. seconds: input time value, which is of the uint32_t type.	–	HDF_STATUS	Sets the timeout period (in seconds) for a watchdog. Ensure that the actual watchdog running time complies with this setting.
getTimeout	wdt: structure pointer to the Watchdog controller at the core layer.	seconds: output time value, which is of the uint32_t type.	HDF_STATUS	Obtains the timeout period of a watchdog.
feed	wdt: structure pointer to the Watchdog controller at the core layer.	–	HDF_STATUS	Feeds a watchdog.

How to Develop

The Watchdog module adaptation involves the following steps:

Instantiate the driver entry.
- Instantiate the HdfDriverEntry structure.
- Call HDF_INIT to register the HdfDriverEntry instance with the HDF.
Configure attribute files.
- Add the deviceNode information to the device_info.hcs file.
- (Optional) Add the watchdog_config.hcs file.
Instantiate the Watchdog controller object.
- Initialize WatchdogCntlr.
- Instantiate WatchdogMethod in the WatchdogCntlr object.
  
  NOTE
  
  For details, see Available APIs.
Debug the driver.
- (Optional) For new drivers, verify basic functions, for example, verify the information returned after the connect operation and whether the watchdog timer is successfully set.

Development Example

The following uses watchdog_hi35xx.c as an example to present the contents that need to be provided by the vendor to implement device functions.

Instantiate the driver entry. The driver entry must be a global variable of the HdfDriverEntry type (defined in hdf_device_desc.h), and the value of moduleName must be the same as that in device_info.hcs. In the HDF, the start address of each HdfDriverEntry object of all loaded drivers is collected to form a segment address space similar to an array for the upper layer to invoke.

Generally, HDF calls the Bind function and then the Init function to load a driver. If Init fails to be called, HDF calls Release to release driver resources and exit.
- Watchdog driver entry reference
```
struct HdfDriverEntry g_watchdogDriverEntry = {
.moduleVersion = 1,
   .Bind = Hi35xxWatchdogBind, // See the Bind function.
.Init = Hi35xxWatchdogInit,  // See the Init function.
.Release = Hi35xxWatchdogRelease, //See the Release function.
.moduleName = "HDF_PLATFORM_WATCHDOG",// (Mandatory) The value must be the same as that of moduleName in the .hcs file.
};
HDF_INIT(g_watchdogDriverEntry);// Call HDF_INIT to register the driver entry with the HDF.
```

Add the deviceNode information to the device_info.hcs file and configure the component attributes in the watchdog_config.hcs file. The deviceNode information is related to registration of the driver entry. The device attribute values are closely related to the default values or value ranges of the WatchdogCntlr members at the core layer.

In this example, there is only one Watchdog controller. If there are multiple Watchdog controllers, you need to add the deviceNode information to the device_info file and add the corresponding device attributes to the watchdog_config file.

device_info.hcs configuration reference

root {
  device_info {
    match_attr = "hdf_manager";
    device_watchdog :: device {// Device node
      device0:: deviceNode {// DeviceNode of the driver
        The policy = 1; // The value 1 indicates that the driver publishes kernel-mode services. The value 2 indicates that the driver publishes user-mode services.
 priority = 20; // Driver startup priority
 permission = 0644; // Permission to create device nodes for the driver
        moduleName = "HDF_PLATFORM_WATCHDOG";             
        // (Mandatory) Driver name. The value must be the same as that of moduleName in the driver entry structure.
        serviceName = "HDF_PLATFORM_WATCHDOG_0";          
       // (Mandatory) Unique name of the service published by the driver.
        deviceMatchAttr = "hisilicon_hi35xx_watchdog_0";  
       // (Mandatory) Keyword matching the private data of the driver. The value must be the same as that of match_attr in the private data configuration table of the driver.
      } 
    }
  }
}

watchdog_config.hcs configuration reference

root {
  platform {
       template watchdog_controller {// Template configuration. In the template, you can configure the common parameters shared by service nodes.
      id = 0;
      match_attr = "";
      regBase = 0x12050000; // (Mandatory) Used for address mapping.
        regStep = 0x1000;   // (Mandatory) Used for address mapping.
    }
    controller_0x12050000 :: watchdog_controller {// (Mandatory) Keyword for matching the private data of the device driver.
        match_attr = "hisilicon_hi35xx_watchdog_0"; // (Mandatory) The value must be the same as that of deviceMatchAttr in device_info.hcs.
      }
      // Configure this parameter when there are multiple watchdogs.
      ...  
    }
}

Initialize the WatchdogCntlr object at the core layer, including initializing the vendor custom structure (passing parameters and data), instantiating WatchdogMethod (used to call underlying functions of the driver) in WatchdogCntlr, and implementing the HdfDriverEntry member functions (Bind, Init, and Release).

Custom structure reference

To the driver, the custom structure carries parameters and data. The values in the watchdog_config.hcs file are read by HDF, and the structure members are initialized through DeviceResourceIface. Some important values, such as the index and the number of pins, are also passed to the WatchdogCntlr object at the core layer.

struct Hi35xxWatchdog {
  struct WatchdogCntlr wdt; // (Mandatory) Carrier that connects the upper and underlying layers. For details, see the following description.
  OsalSpinlock lock;
  volatile unsigned char *regBase;// [Mandatory] Used for address mapping.
         uint32_t phyBase;   // (Mandatory) Used for address mapping.
      uint32_t regStep;  // (Mandatory) Used for address mapping.
};
// WatchdogCntlr is the core layer controller structure. Its members are assigned with values by using the Init function.
struct WatchdogCntlr {
  struct IDeviceIoService service;// Driver service
  struct HdfDeviceObject *device; // Drive device
  OsalSpinlock lock; // This variable implements the spinlock function.
  struct WatchdogMethod *ops; // Interface callback
  int16_t wdtId; // ID of the watchdog device
  void *priv; // Save the pointer.
};

Instantiate the callback function structure WatchdogMethod in WatchdogCntlr. Other members are initialized by using the Init and Bind functions.

static struct WatchdogMethod g_method = {
    .getStatus = Hi35xxWatchdogGetStatus,
    .start = Hi35xxWatchdogStart,
    .stop = Hi35xxWatchdogStop,
    .setTimeout = Hi35xxWatchdogSetTimeout,
    .getTimeout = Hi35xxWatchdogGetTimeout,
    .feed = Hi35xxWatchdogFeed,
};

Init and Bind functions

Input parameters:

HdfDeviceObject: device object created by the HDF for each driver. It stores device-related private data and service APIs.

Return values:

HDF_STATUS (The following table lists some status. For details about other status, see HDF_STATUS in the //drivers/framework/include/utils/hdf_base.h file.)

Table 2 Input parameters and return values of the Init and Bind functions

Status (Value)	Description
HDF_ERR_INVALID_OBJECT	Failed to locate the watchdog device
HDF_ERR_MALLOC_FAIL	Failed to allocate memory
HDF_ERR_IO	I/O error
HDF_SUCCESS	Initialization successful
HDF_FAILURE	Initialization failed

Function description:

Initializes the custom structure object and WatchdogCntlr, and calls the WatchdogCntlrAdd function at the core layer.

// Generally, the Init function initializes the members of the Hi35xxWatchdog structure based on the attribute values of the input parameter (HdfDeviceObject).
// In this example, the Bind function initializes the Hi35xxWatchdog structure.
static int32_t Hi35xxWatchdogInit(struct HdfDeviceObject *device)
{
(void)device;
return HDF_SUCCESS;
}

static int32_t Hi35xxWatchdogBind(struct HdfDeviceObject *device)
{
int32_t ret;
struct Hi35xxWatchdog *hwdt = NULL;
...
hwdt = (struct Hi35xxWatchdog *)OsalMemCalloc(sizeof(*hwdt));// Apply for memory for the Hi35xxWatchdog structure.
...
hwdt->regBase = OsalIoRemap(hwdt->phyBase, hwdt->regStep); // Address mapping
...
hwdt->wdt.priv = (void *)device->property;// (Optional) Assign the device attribute values to priv. However, priv is not called subsequently.
                                            //If priv needs to be called, instantiate the getPriv and releasePriv member functions in WatchdogMethod.
hwdt->wdt.ops = &g_method; // (Mandatory) Assign the instantiated objects to the ops member so that the top layer can invoke the WatchdogMethod member functions.
hwdt->wdt.device = device; // (Mandatory) Enable conversion between HdfDeviceObject and WatchdogcCntlr.
ret = WatchdogCntlrAdd(&hwdt->wdt);   // (Mandatory) Call this function to initialize the structure of the core layer. The driver accesses the platform core layer only after a success signal is returned.
if (ret != HDF_SUCCESS) {// If the operation fails, release the resources used by the Init function.
    OsalIoUnmap((void *)hwdt->regBase);
    OsalMemFree(hwdt);
    return ret;
}    
return HDF_SUCCESS;
}

Release function

Input parameters:

HdfDeviceObject: device object created by the HDF for each driver. It stores device-related private data and service APIs.

Return values:

–

Function description:

Releases the memory and deletes the controller. This function assigns a value to the Release API in the driver entry structure. When the HDF fails to call the Init function to initialize the driver, the Release function can be called to release driver resources. All forced conversion operations for obtaining the corresponding object can be successful only when the Init function has the corresponding value assignment operations.

static void Hi35xxWatchdogRelease(struct HdfDeviceObject *device)
{
struct WatchdogCntlr *wdt = NULL;
struct Hi35xxWatchdog *hwdt = NULL;
...
wdt = WatchdogCntlrFromDevice(device);// Convert HdfDeviceObject to WatchdogCntlr by the service member.
                                        //return (device == NULL) ? NULL : (struct WatchdogCntlr *)device->service;
if (wdt == NULL) {
    return;
}
WatchdogCntlrRemove(wdt); // Core layer function used to execute wdt->device->service = NULL and release cntlr->lock.
hwdt = (struct Hi35xxWatchdog *)wdt; // Convert WatchdogCntlr to HimciHost.
if (hwdt->regBase != NULL) {// Remove address mapping.
    OsalIoUnmap((void *)hwdt->regBase);
    hwdt->regBase = NULL;
}
OsalMemFree(hwdt); // Release the memory occupied by the vendor-defined objects.
}