WinCE

If you are experiencing system performance issues in ROM based File systems, here is a nice tweak to boost up the performance. Most of the times, this slowdown will be due to constant registry flushing in to ROM in background.

[HKEY_LOCAL_MACHINE\init\BootVars]
"RegistryFlags"=dword:2

If this variable is set to 1, it will enable aggressive flushing of registry on to ROM. Setting it to 2 will disable background flushing and can improve performance of system significantly.

Reference: http://msdn.microsoft.com/en-us/library/aa914382.aspx

In one of my previous posts, I mentioned about cloning OALIOCTL, was thinking of writing about it. But Bruce have already written about. And it was my reference too. So check it out

It is assumed that , the OAL code is cloned to the BSP under development, including the ioctl code. For the purpose of explaining the process, the Mainstone III reference platform will be used.

The BSP specific, ioctl will be located under the directory, MAINSTONEIII\SRC\OAL\OALLIB\ioctl.c.

Now lets assume that we need to implement an ioctl to flag the backing up of system alarm setting during shutdown.

• Define a new function in ioctl.c as:

BOOL OALIoCtlHalAlarmSet
               (   UINT32 code, VOID *pInpBuffer,
                   UINT32 inpSize, VOID *pOutBuffer,
                 UINT32 outSize, UINT32 *pOutSize)
{
g_oalIoCtlUserAlarmSet = TRUE;
return(TRUE);
}

• Define a macro for the new IOCTL.

#define FILE_DEVICE_CUST_OEM   32806

#define IOCTL_DDK_SET_ALARM_FLAG        \
CTL_CODE(FILE_DEVICE_CUST_OEM, 0x0100, METHOD_BUFFERED, FILE_ANY_ACCESS)

• Modify g_oalIoCtlTable variable in ioctl.c to add the new ioctl mapping:

const OAL_IOCTL_HANDLER g_oalIoCtlTable[] = {
.....
{
IOCTL_DDK_SET_ALARM_FLAG,
0,
OALIoCtlHalAlarmSet
},
#include 
.....
}

Now we have a kernel ioctl, which can be invoked from any section coming under kernel address space. For making this IOCTL accessible from User space, we need to customise (clone) OALIOCTL, which will be described in another post in detail

On resuming from sleep mode of PXA27X, the usb client wont be working straight away. No insertion events will be detected and the device will be shown as an uknown device in PC.

For overcoming this situation, we have to clear the OTGPH bit in PSSR (Power Manager Sleep Status Register). This is a write to clear bit.

OTGPH will be set when entering sleep mode when writing the PWRMODE register and indicates that the OTG pad is retaining state. So after resuming, the USB OTG, UDC and UHC should be configured, then only clear the OTGPH bit.

Referece : Marvell PXA27X Processor Developer Manual, November 3 , 2006

For monitoring events for a network interface, the notification request ioctl IOCTL_NDISUIO_REQUEST_NOTIFICATION in NDISUIO driver can be used.

By using this Notification mechanism, we can capture events for each network interface in Windows CE such as

• Bind
• Unbind
• Power Up
• Power down
• etc...

A sample implementation is provided in the NDISPWR driver in PUBLIC code
(WINCE600\PUBLIC\COMMON\OAK\DRIVERS\NETSAMP\NDISPWR)

In power manager, the PDD has a certain set of events that it monitors. For eg:

• PM_BOOTPHASE2_EVENT
• PM_SYSTEM_API_EVENT etc

For more information on events each PDD handles, check the Power manager code available in PUBLIC code (WINCE600\PUBLIC\COMMON\OAK\DRIVERS\PM\PDD).

In those events there is event PM_SYSTEM_TIMEIDLE_RESET (PowerManager/SystemIdleTimerReset), which can used to reset the system activity timer. Check out the following piece of code for doing so.

  HANDLE hSysTmrReset = CreateEvent(NULL, FALSE, FALSE, _T("PowerManager/SystemIdleTimerReset"));
  BOOL bExit = FALSE;
  if (INVALID_HANDLE_VALUE != hSysTmrReset )
  {
      while (FALSE == bExit)
      {
          ResetEvent(hSysTmrReset);
          Sleep(1000);
          SetEvent(hSysTmrReset);
       
          RETAILMSG(TRUE, (TEXT("Reset\r\n")));
          Sleep(20000);
      }
      CloseHandle (hSysTmrReset );
  }
  return 0;

This system, code will keep the system alive by resetting the timer every 20 seconds. I have tested this code and seems to be working. But needs to analyze the system performance on doing so.

To enable aggressive scanning for wifi network (preferred or non-preferred ones) in Wireless Zero Configuration in Windows CE, use this registry setting:

[HKEY_LOCAL_MACHINE\Comm\WiFi]
ScanInterval: dword:5

This will set WZC to scan for network every 5 seconds. By default, it is set to 60 seconds. Try tuning this value as per your requirement.