NvmExpressDxe TimerEvent frequency

NvmExpressDxe TimerEvent frequency

[Arka Sharma]

Hi,

UEFI Driver Write Guide section 5.1.6 says
"UEFI system firmware uses a hardware timer interrupt to measure time.
These. These
time measurements are used to determine when enough time has passed to signal a
timer event programmed with SetTimer(). In most systems, the timer interrupt is
generated every 10 ms to 50 ms, but the UEFI Specification does not require any
specific interrupt rate. This lack of specificity means that a
periodic timer programmed
with a period much smaller than 10 ms may only be signaled every 10 ms
to 50 ms.". So in case of NvmExpressDxe the Private->TimerEvent is set
with 1 ms, so the frequency of the routine ProcessAsyncTaskList might
be more than 1 ms as per the frequency of the timer interrupt ?

Regards,
Arka

Re: NvmExpressDxe TimerEvent frequency

[Tian, Feng]

Yes.

For example, old platforms usually use 50ms as timer interval. So at such platforms, even the code is programming to use 1 ms timer, the actual trigger time interval is 50ms.

Thanks
Feng

-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Arka Sharma
Sent: Sunday, April 9, 2017 12:41 PM
To: edk2-devel@lists.01.org
Subject: [edk2] NvmExpressDxe TimerEvent frequency

Hi,

UEFI Driver Write Guide section 5.1.6 says "UEFI system firmware uses a hardware timer interrupt to measure time.
These. These
time measurements are used to determine when enough time has passed to signal a timer event programmed with SetTimer(). In most systems, the timer interrupt is generated every 10 ms to 50 ms, but the UEFI Specification does not require any specific interrupt rate. This lack of specificity means that a periodic timer programmed with a period much smaller than 10 ms may only be signaled every 10 ms to 50 ms.". So in case of NvmExpressDxe the Private->TimerEvent is set with 1 ms, so the frequency of the routine ProcessAsyncTaskList might be more than 1 ms as per the frequency of the timer interrupt ?

Regards,
Arka
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