[PATCH v1] ArmPkg: Fix bug in Generic Waitchdog driver

[PATCH v1] ArmPkg: Fix bug in Generic Waitchdog driver

[AlexeiFedorov]

In ArmPkg\Drivers\GenericWatchdogDxe\GenericWatchdogDxe.c
the following functions
WatchdogWriteOffsetRegister();
WatchdogWriteCompareRegister();
WatchdogEnable();
WatchdogDisable();
provide write access to ARM Generic Watchdog registers and
use the values returned by MmioWrite32() and MmioWrite64()
as EFI_STATUS return codes.
Because MmioWriteXY() return the value passed as its write
parameter, Generic Watchdog access functions can return error code
which is different from EFI_SUCCESS, e.g. the following call
    Status = WatchdogWriteOffsetRegister (MAX_UINT32);
    if (EFI_ERROR (Status)) {
      return Status;
    }
will return MAX_UINT32 defined in MdePkg\Include\Base.h as
 #define MAX_UINT32  ((UINT32)0xFFFFFFFF)

This commit declares all the functions listed above as VOID
and removes the code for checking their return values.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Alexei Fedorov <alexei.fedorov@arm.com>
Reviewed-by:   Evan Lloyd <evan.lloyd@arm.com>
---
All the changes can be seen at
https://github.com/AlexeiFedorov/edk2/tree/84_generic_timer_v1

Notes:
    v1:
    - Fix functions writing to ARM Generic Watchdog's registers  [Alexei]

 ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c | 37 +++++++++-----------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
index 252ba5bf321e379ef440830cab468af7c55905b3..3180f011253639c408b7151c79c2106a352c7340 100644
--- a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
+++ b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
@@ -1,6 +1,6 @@
 /** @file
 *
-*  Copyright (c) 2013-2017, ARM Limited. All rights reserved.
+*  Copyright (c) 2013-2018, ARM Limited. All rights reserved.
 *
 *  This program and the accompanying materials
 *  are licensed and made available under the terms and conditions of the BSD
@@ -43,36 +43,36 @@ UINT64 mNumTimerTicks = 0;
 
 EFI_HARDWARE_INTERRUPT2_PROTOCOL *mInterruptProtocol;
 
-EFI_STATUS
+VOID
 WatchdogWriteOffsetRegister (
   UINT32  Value
   )
 {
-  return MmioWrite32 (GENERIC_WDOG_OFFSET_REG, Value);
+  MmioWrite32 (GENERIC_WDOG_OFFSET_REG, Value);
 }
 
-EFI_STATUS
+VOID
 WatchdogWriteCompareRegister (
   UINT64  Value
   )
 {
-  return MmioWrite64 (GENERIC_WDOG_COMPARE_VALUE_REG, Value);
+  MmioWrite64 (GENERIC_WDOG_COMPARE_VALUE_REG, Value);
 }
 
-EFI_STATUS
+VOID
 WatchdogEnable (
   VOID
   )
 {
-  return MmioWrite32 (GENERIC_WDOG_CONTROL_STATUS_REG, GENERIC_WDOG_ENABLED);
+  MmioWrite32 (GENERIC_WDOG_CONTROL_STATUS_REG, GENERIC_WDOG_ENABLED);
 }
 
-EFI_STATUS
+VOID
 WatchdogDisable (
   VOID
   )
 {
-  return MmioWrite32 (GENERIC_WDOG_CONTROL_STATUS_REG, GENERIC_WDOG_DISABLED);
+  MmioWrite32 (GENERIC_WDOG_CONTROL_STATUS_REG, GENERIC_WDOG_DISABLED);
 }
 
 /** On exiting boot services we must make sure the Watchdog Timer
@@ -163,9 +163,7 @@ WatchdogRegisterHandler (
                            then the watchdog timer is disabled.
 
   @retval EFI_SUCCESS           The watchdog timer has been programmed to fire
-                                in Time  100ns units.
-  @retval EFI_DEVICE_ERROR      A watchdog timer could not be programmed due
-                                to a device error.
+                                in TimerPeriod 100ns units.
 
 **/
 EFI_STATUS
@@ -176,12 +174,12 @@ WatchdogSetTimerPeriod (
   )
 {
   UINTN       SystemCount;
-  EFI_STATUS  Status;
 
   // if TimerPeriod is 0, this is a request to stop the watchdog.
   if (TimerPeriod == 0) {
     mNumTimerTicks = 0;
-    return WatchdogDisable ();
+    WatchdogDisable ();
+    return EFI_SUCCESS;
   }
 
   // Work out how many timer ticks will equate to TimerPeriod
@@ -195,19 +193,16 @@ WatchdogSetTimerPeriod (
        because enabling the watchdog causes an "explicit refresh", which
        clobbers the compare register (WCV). In order to make sure this doesn't
        trigger an interrupt, set the offset to max. */
-    Status = WatchdogWriteOffsetRegister (MAX_UINT32);
-    if (EFI_ERROR (Status)) {
-      return Status;
-    }
+    WatchdogWriteOffsetRegister (MAX_UINT32);
     WatchdogEnable ();
     SystemCount = ArmGenericTimerGetSystemCount ();
-    Status      = WatchdogWriteCompareRegister (SystemCount + mNumTimerTicks);
+    WatchdogWriteCompareRegister (SystemCount + mNumTimerTicks);
   } else {
-    Status = WatchdogWriteOffsetRegister ((UINT32)mNumTimerTicks);
+    WatchdogWriteOffsetRegister ((UINT32)mNumTimerTicks);
     WatchdogEnable ();
   }
 
-  return Status;
+  return EFI_SUCCESS;
 }
 
 /**
-- 
'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'

Re: [PATCH v1] ArmPkg: Fix bug in Generic Waitchdog driver

[Ard Biesheuvel]

On 27 April 2018 at 15:58, AlexeiFedorov <alexei.fedorov@arm.com> wrote:
> In ArmPkg\Drivers\GenericWatchdogDxe\GenericWatchdogDxe.c
> the following functions
> WatchdogWriteOffsetRegister();
> WatchdogWriteCompareRegister();
> WatchdogEnable();
> WatchdogDisable();
> provide write access to ARM Generic Watchdog registers and
> use the values returned by MmioWrite32() and MmioWrite64()
> as EFI_STATUS return codes.
> Because MmioWriteXY() return the value passed as its write
> parameter, Generic Watchdog access functions can return error code
> which is different from EFI_SUCCESS, e.g. the following call
>     Status = WatchdogWriteOffsetRegister (MAX_UINT32);
>     if (EFI_ERROR (Status)) {
>       return Status;
>     }
> will return MAX_UINT32 defined in MdePkg\Include\Base.h as
>  #define MAX_UINT32  ((UINT32)0xFFFFFFFF)
>
> This commit declares all the functions listed above as VOID
> and removes the code for checking their return values.
>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Alexei Fedorov <alexei.fedorov@arm.com>
> Reviewed-by:   Evan Lloyd <evan.lloyd@arm.com>
> ---
> All the changes can be seen at
> https://github.com/AlexeiFedorov/edk2/tree/84_generic_timer_v1
>
> Notes:
>     v1:
>     - Fix functions writing to ARM Generic Watchdog's registers  [Alexei]
>
>  ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c | 37 +++++++++-----------
>  1 file changed, 16 insertions(+), 21 deletions(-)
>

Nice catch

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Pushed as 8fe18cba7694

Thanks


> diff --git a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
> index 252ba5bf321e379ef440830cab468af7c55905b3..3180f011253639c408b7151c79c2106a352c7340 100644
> --- a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
> +++ b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
> @@ -1,6 +1,6 @@
>  /** @file
>  *
> -*  Copyright (c) 2013-2017, ARM Limited. All rights reserved.
> +*  Copyright (c) 2013-2018, ARM Limited. All rights reserved.
>  *
>  *  This program and the accompanying materials
>  *  are licensed and made available under the terms and conditions of the BSD
> @@ -43,36 +43,36 @@ UINT64 mNumTimerTicks = 0;
>
>  EFI_HARDWARE_INTERRUPT2_PROTOCOL *mInterruptProtocol;
>
> -EFI_STATUS
> +VOID
>  WatchdogWriteOffsetRegister (
>    UINT32  Value
>    )
>  {
> -  return MmioWrite32 (GENERIC_WDOG_OFFSET_REG, Value);
> +  MmioWrite32 (GENERIC_WDOG_OFFSET_REG, Value);
>  }
>
> -EFI_STATUS
> +VOID
>  WatchdogWriteCompareRegister (
>    UINT64  Value
>    )
>  {
> -  return MmioWrite64 (GENERIC_WDOG_COMPARE_VALUE_REG, Value);
> +  MmioWrite64 (GENERIC_WDOG_COMPARE_VALUE_REG, Value);
>  }
>
> -EFI_STATUS
> +VOID
>  WatchdogEnable (
>    VOID
>    )
>  {
> -  return MmioWrite32 (GENERIC_WDOG_CONTROL_STATUS_REG, GENERIC_WDOG_ENABLED);
> +  MmioWrite32 (GENERIC_WDOG_CONTROL_STATUS_REG, GENERIC_WDOG_ENABLED);
>  }
>
> -EFI_STATUS
> +VOID
>  WatchdogDisable (
>    VOID
>    )
>  {
> -  return MmioWrite32 (GENERIC_WDOG_CONTROL_STATUS_REG, GENERIC_WDOG_DISABLED);
> +  MmioWrite32 (GENERIC_WDOG_CONTROL_STATUS_REG, GENERIC_WDOG_DISABLED);
>  }
>
>  /** On exiting boot services we must make sure the Watchdog Timer
> @@ -163,9 +163,7 @@ WatchdogRegisterHandler (
>                             then the watchdog timer is disabled.
>
>    @retval EFI_SUCCESS           The watchdog timer has been programmed to fire
> -                                in Time  100ns units.
> -  @retval EFI_DEVICE_ERROR      A watchdog timer could not be programmed due
> -                                to a device error.
> +                                in TimerPeriod 100ns units.
>
>  **/
>  EFI_STATUS
> @@ -176,12 +174,12 @@ WatchdogSetTimerPeriod (
>    )
>  {
>    UINTN       SystemCount;
> -  EFI_STATUS  Status;
>
>    // if TimerPeriod is 0, this is a request to stop the watchdog.
>    if (TimerPeriod == 0) {
>      mNumTimerTicks = 0;
> -    return WatchdogDisable ();
> +    WatchdogDisable ();
> +    return EFI_SUCCESS;
>    }
>
>    // Work out how many timer ticks will equate to TimerPeriod
> @@ -195,19 +193,16 @@ WatchdogSetTimerPeriod (
>         because enabling the watchdog causes an "explicit refresh", which
>         clobbers the compare register (WCV). In order to make sure this doesn't
>         trigger an interrupt, set the offset to max. */
> -    Status = WatchdogWriteOffsetRegister (MAX_UINT32);
> -    if (EFI_ERROR (Status)) {
> -      return Status;
> -    }
> +    WatchdogWriteOffsetRegister (MAX_UINT32);
>      WatchdogEnable ();
>      SystemCount = ArmGenericTimerGetSystemCount ();
> -    Status      = WatchdogWriteCompareRegister (SystemCount + mNumTimerTicks);
> +    WatchdogWriteCompareRegister (SystemCount + mNumTimerTicks);
>    } else {
> -    Status = WatchdogWriteOffsetRegister ((UINT32)mNumTimerTicks);
> +    WatchdogWriteOffsetRegister ((UINT32)mNumTimerTicks);
>      WatchdogEnable ();
>    }
>
> -  return Status;
> +  return EFI_SUCCESS;
>  }
>
>  /**
> --
> 'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'
>
>