[edk2-devel] On RPi4 and Juno, gBS->Stall(1) takes 10us and 100us respectively

[Rebecca Cran]

Thanks. RPi4 and Juno use EmbeddedPkg/MetronomeDxe 
(https://github.com/tianocore/edk2/blob/master/EmbeddedPkg/MetronomeDxe/Metronome.c#L54) 
which uses the PCD PcdMetronomeTickPeriod.

JunoPkg overrides that to 1000, while RPi4 uses the default of 100. 
Given that the clocks run at 50MHz and 54MHz, I think the tick period 
should be 1 (1 100-ns unit, giving a clock frequency of 10MHz)?

-- 
Rebecca Cran



On 11/28/22 12:51, Andrew Fish via groups.io wrote:
> Rebecca,
> 
> gBS->Stall() is built on top [1] of the Metronome Architectural Protocol 
> [2]. You should look at how the platform implements the Metronome 
> Architectural Protocol.
> 
> It looks like most platform implement a generic Metronome Driver[3] that 
> just sits on top of the platforms TimerLib [4] implementation.
> 
> You can find the TimerLib implementations via:
> 
> $ git grep TimerLib -- \*.inf | grep LIBRARY_CLASS
> 
> ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.inf:14:  LIBRARY_CLASS    
>                = TimerLib
> 
> EmbeddedPkg/Library/DebugAgentTimerLibNull/DebugAgentTimerLibNull.inf:19:  LIBRARY_CLASS                  = DebugAgentTimerLib|SEC BASE DXE_CORE
> 
> EmulatorPkg/Library/DxeCoreTimerLib/DxeCoreTimerLib.inf:22:  
> LIBRARY_CLASS                  = TimerLib|DXE_CORE DXE_DRIVER 
> DXE_RUNTIME_DRIVER UEFI_DRIVER UEFI_APPLICATION
> 
> EmulatorPkg/Library/DxeTimerLib/DxeTimerLib.inf:22:  LIBRARY_CLASS      
>              = TimerLib|DXE_DRIVER DXE_RUNTIME_DRIVER UEFI_DRIVER 
> UEFI_APPLICATION
> 
> EmulatorPkg/Library/PeiTimerLib/PeiTimerLib.inf:22:  LIBRARY_CLASS      
>              = TimerLib|PEIM PEI_CORE SEC
> 
> MdePkg/Library/BaseTimerLibNullTemplate/BaseTimerLibNullTemplate.inf:23:  LIBRARY_CLASS                  = TimerLib
> 
> MdePkg/Library/SecPeiDxeTimerLibCpu/SecPeiDxeTimerLibCpu.inf:30:  
> LIBRARY_CLASS                  = TimerLib
> 
> OvmfPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.inf:17:  LIBRARY_CLASS  = 
> TimerLib|PEI_CORE PEIM DXE_CORE
> 
> OvmfPkg/Library/AcpiTimerLib/BaseAcpiTimerLibBhyve.inf:18:  
> LIBRARY_CLASS  = TimerLib
> 
> OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf:16:  LIBRARY_CLASS  
> = TimerLib|SEC
> 
> OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf:17:  LIBRARY_CLASS  = 
> TimerLib|DXE_DRIVER DXE_RUNTIME_DRIVER DXE_SMM_DRIVER UEFI_DRIVER 
> UEFI_APPLICATION SMM_CORE
> 
> PcAtChipsetPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.inf:21:  
> LIBRARY_CLASS                  = TimerLib|SEC PEI_CORE PEIM
> 
> PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf:21:  
> LIBRARY_CLASS                  = TimerLib|DXE_CORE DXE_DRIVER 
> DXE_RUNTIME_DRIVER DXE_SMM_DRIVER UEFI_APPLICATION UEFI_DRIVER SMM_CORE
> 
> PcAtChipsetPkg/Library/AcpiTimerLib/PeiAcpiTimerLib.inf:21:  
> LIBRARY_CLASS                  = TimerLib|PEI_CORE PEIM
> 
> PcAtChipsetPkg/Library/AcpiTimerLib/StandaloneMmAcpiTimerLib.inf:23:  
> LIBRARY_CLASS                  = TimerLib|MM_CORE_STANDALONE MM_STANDALONE
> 
> UefiCpuPkg/Library/CpuTimerLib/BaseCpuTimerLib.inf:18:  LIBRARY_CLASS    
>                = TimerLib
> 
> UefiCpuPkg/Library/SecPeiDxeTimerLibUefiCpu/SecPeiDxeTimerLibUefiCpu.inf:30:  LIBRARY_CLASS                  = TimerLib
> 
> UefiPayloadPkg/Library/AcpiTimerLib/AcpiTimerLib.inf:15:  LIBRARY_CLASS  
>                  = TimerLib
> 
> 
> So I’d guess your platform is using the ArmArchTimerLi [5]. If that is 
> the case I’d look at the value of PcdArmArchTimerFreqInHz if it is zero 
> then I think you are running on the default ARM timer value.
> 
> If you are using the stock stuff and all your TimerLib instances are the 
> same in all your drivers then the TimerLib is also abstraction the 
> performance measure.
> 
> This is probably not helpful but the UEFI Spec defines that Stall() 
> delays for at least the requested amount of time, with no upper bound on 
> how long it can take.
> 
> [1] 
> https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Dxe/Misc/Stall.c#L49 <https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Dxe/Misc/Stall.c#L49>
> [2] 
> https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Protocol/Metronome.h#L25 <https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Protocol/Metronome.h#L25>
> [3] 
> https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/Metronome/Metronome.c#L61 <https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/Metronome/Metronome.c#L61>
> [4] 
> https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Library/TimerLib.h <https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Library/TimerLib.h>
> [5] 
> https://github.com/tianocore/edk2/blob/master/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c#L18 <https://github.com/tianocore/edk2/blob/master/ArmPkg/Library/ArmArchTimerLib/ArmArchTimerLib.c#L18>
> 
> Thanks,
> 
> Andrew Fish
> 
> 
>> On Nov 28, 2022, at 11:02 AM, Rebecca Cran <quic_rcran at quicinc.com> wrote:
>>
>> I've been doing some work on USB and ended up realizing that 
>> gBS->Stall(1) is taking much longer than it should: on my Juno R2 it's 
>> stalling for 100 us, while on my Raspberry Pi 4 it's 10 us.
>>
>> This appears to be causing a USB bulk transfer request that asks for a 
>> 1ms timeout taking 100ms on the Juno.
>>
>> I'm measuring the delay with the following code:
>>
>>
>> UINT64 First = GetPerformanceCounter ();
>>
>> gBS->Stall (XHC_1_MICROSECOND);
>>
>> UINT64 Second = GetPerformanceCounter ();
>>
>> UINT64 FirstNs = GetTimeInNanoSecond (First);
>> UINT64 SecondNs = GetTimeInNanoSecond (Second);
>>
>> DEBUG ((DEBUG_INFO, "Stalled for %llu ns (%llu ms)\n", (SecondNs - 
>> FirstNs), (SecondNs - FirstNs) / 1024 / 1024));
>>
>>
>>
>> I see output such as:
>>
>> Stalled for 10500 ns (0 ms)
>>
>>
>> -- 
>> Rebecca Cran
>>
>>
>>
>>
>>
> 
> 


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