Yes. But when the system goes back to Legacy Environment we need to change the
timer interval to 54ms as this is IBM standard .
Thanks,
Ramesh
From: galla rao [mailto:gallagnv....@gmail.com]
Sent: Monday, September 16, 2013 6:55 PM
To: edk2-devel@lists.sourceforge.net
Subject: Re: [edk2] SetTimer Granularity in uEFI
Thanks Ramesh for your inputs
Does it mean that if platform BIOS supports HPET timer
I can have a callback for lesser granularity than 54ms
Hope this is what you are trying to convey
Thanks Ramesh & Sergey for your inputs
I would try and see if it helps me
On Mon, Sep 16, 2013 at 5:49 PM, Ramesh R.
<rame...@ami.com<mailto:rame...@ami.com>> wrote:
Hello Ranga,
The Legacy environment assumed that 18.4 times Timer 0 gets generated per
Second. It means Timer 0 IRQ raised for every 54ms.
By using the HPET timer we could change the timer frequency to lesser values
and when we switch to Legacy environment we could change it back to 54ms as
interval.
Thanks,
Ramesh
From: galla rao [mailto:gallagnv....@gmail.com<mailto:gallagnv....@gmail.com>]
Sent: Monday, September 16, 2013 4:23 PM
To: edk2-devel@lists.sourceforge.net<mailto:edk2-devel@lists.sourceforge.net>
Subject: [edk2] SetTimer Granularity in uEFI
Hello All,
Can anyone help me understand what is the minimum Timer Granularity for
gBS->SetTimer
When i have written a callback with 50ms(milli seconds), The calls seems to be
taking a value close
to 50ms
In the 8254Timerdxe the following comments are given about timer ticks
//
// The PCAT 8253/8254 has an input clock at 1.193182 MHz and Timer 0 is
// initialized as a 16 bit free running counter that generates an
interrupt(IRQ0)
// each time the counter rolls over.
//
// 65536 counts
// ---------------- * 1,000,000 uS/S = 54925.4 uS = 549254 * 100 ns
// 1,193,182 Hz
//
// The default timer tick duration is set to 10 ms = 100000 100 ns units
//
Based on the above details on x86-IA64 architecture
54925.4uS would be close to 50ms(milli seconds)
Does it means minimum granularity is 50ms for a callback to get called. For a
10ms callback i am not seeing
a callback getting called every 10ms
Can I use anyother Timer Mechanisms from chipset for a shorter callbacks than
50ms to improve my IO repsonse of the device?
Please provide your inputs & suggestions.
Thanks
Ranga
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