Re: [edk2-devel] [PATCH v3 2/3] ArmPkg: Introduce global mTimerPeriod and remove calculation

["Sami Mujawar" <sami.mujawar@arm.com>]

Hi Rebecca,

I have a minor suggestion marked inline as [SAMI], otherwise this patch looks good to me.

Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>

Regards,

Sami Mujawar

On 05/01/2024, 05:15, "Rebecca Cran" <rebecca@os.amperecomputing.com <mailto:rebecca@os.amperecomputing.com>> wrote:


The calculation of the timer period was broken. Introduce a global
mTimerPeriod so the calculation can be removed. Since mTimerFrequencyHz
is only used in one place, remove the global and make it a local
variable. Do the same with mNumTimerTicks.


Signed-off-by: Rebecca Cran <rebecca@os.amperecomputing.com <mailto:rebecca@os.amperecomputing.com>>
---
ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c | 36 ++++++++++++++----------------
1 file changed, 17 insertions(+), 19 deletions(-)


diff --git a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
index f8c39458a53a..78cee62a19d6 100644
--- a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
+++ b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
@@ -28,13 +28,10 @@
in a second */
#define TIME_UNITS_PER_SECOND 10000000


-// Tick frequency of the generic timer basis of the generic watchdog.
-STATIC UINTN mTimerFrequencyHz = 0;
-
/* In cases where the compare register was set manually, information about
how long the watchdog was asked to wait cannot be retrieved from hardware.
It is therefore stored here. 0 means the timer is not running. */
-STATIC UINT64 mNumTimerTicks = 0;
+STATIC UINT64 mTimerPeriod = 0;


#define MAX_UINT48 0xFFFFFFFFFFFFULL


@@ -91,7 +88,8 @@ WatchdogExitBootServicesEvent (
)
{
WatchdogDisable ();
- mNumTimerTicks = 0;
+ mTimerPeriod = 0;
+ mExitedBootServices = TRUE;
}


/* This function is called when the watchdog's first signal (WS0) goes high.
@@ -106,7 +104,6 @@ WatchdogInterruptHandler (
)
{
STATIC CONST CHAR16 ResetString[] = L"The generic watchdog timer ran out.";
- UINT64 TimerPeriod;


WatchdogDisable ();


@@ -119,8 +116,7 @@ WatchdogInterruptHandler (
// the timer period plus 1.
//
if (mWatchdogNotify != NULL) {
- TimerPeriod = ((TIME_UNITS_PER_SECOND / mTimerFrequencyHz) * mNumTimerTicks);
- mWatchdogNotify (TimerPeriod + 1);
+ mWatchdogNotify (mTimerPeriod + 1);
}


gRT->ResetSystem (
@@ -200,22 +196,27 @@ WatchdogSetTimerPeriod (
IN UINT64 TimerPeriod // In 100ns units
)
{
- UINTN SystemCount;
+ UINTN SystemCount;
+ UINT64 TimerFrequencyHz;
+ UINT64 NumTimerTicks;


// if TimerPeriod is 0, this is a request to stop the watchdog.
if (TimerPeriod == 0) {
- mNumTimerTicks = 0;
+ mTimerPeriod = 0;
WatchdogDisable ();
return EFI_SUCCESS;
}


// Work out how many timer ticks will equate to TimerPeriod
- mNumTimerTicks = (mTimerFrequencyHz * TimerPeriod) / TIME_UNITS_PER_SECOND;
+ TimerFrequencyHz = ArmGenericTimerGetTimerFreq ();
+ ASSERT (TimerFrequencyHz != 0);
+ mTimerPeriod = TimerPeriod;
+ NumTimerTicks = (TimerFrequencyHz * TimerPeriod) / TIME_UNITS_PER_SECOND;


/* If the number of required ticks is greater than the max the watchdog's
offset register (WOR) can hold, we need to manually compute and set
the compare register (WCV) */
- if (mNumTimerTicks > MAX_UINT48) {
+ if (NumTimerTicks > MAX_UINT48) {
/* We need to enable the watchdog *before* writing to the compare register,
because enabling the watchdog causes an "explicit refresh", which
clobbers the compare register (WCV). In order to make sure this doesn't
@@ -223,9 +224,9 @@ WatchdogSetTimerPeriod (
WatchdogWriteOffsetRegister (MAX_UINT48);
WatchdogEnable ();
SystemCount = ArmGenericTimerGetSystemCount ();
- WatchdogWriteCompareRegister (SystemCount + mNumTimerTicks);
+ WatchdogWriteCompareRegister (SystemCount + NumTimerTicks);
} else {
- WatchdogWriteOffsetRegister (mNumTimerTicks);
+ WatchdogWriteOffsetRegister (NumTimerTicks);
WatchdogEnable ();
}


@@ -260,7 +261,7 @@ WatchdogGetTimerPeriod (
return EFI_INVALID_PARAMETER;
}


- *TimerPeriod = ((TIME_UNITS_PER_SECOND / mTimerFrequencyHz) * mNumTimerTicks);
+ *TimerPeriod = mTimerPeriod;


return EFI_SUCCESS;
}
@@ -327,9 +328,6 @@ GenericWatchdogEntry (
This will avoid conflicts with the universal watchdog */
ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiWatchdogTimerArchProtocolGuid);


- mTimerFrequencyHz = ArmGenericTimerGetTimerFreq ();
- ASSERT (mTimerFrequencyHz != 0);
-
// Install interrupt handler
Status = mInterruptProtocol->RegisterInterruptSource (
mInterruptProtocol,
@@ -371,7 +369,7 @@ GenericWatchdogEntry (
);
ASSERT_EFI_ERROR (Status);


- mNumTimerTicks = 0;
+ mTimerPeriod = 0;
[SAMI] I think we do not need to initialise mTimerPeriod to 0 here as it would already be 0, right?
WatchdogDisable ();


return EFI_SUCCESS;
-- 
2.34.1







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