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Re: [PATCH 7/7] Add support for ARM UEFI ("EFI") platforms

From: Francesco Lavra
Subject: Re: [PATCH 7/7] Add support for ARM UEFI ("EFI") platforms
Date: Mon, 01 Apr 2013 16:49:34 +0200
User-agent: Mozilla/5.0 (X11; Linux i686; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1

On 04/01/2013 04:16 PM, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> On 01.04.2013 16:10, Francesco Lavra wrote:
>> On 04/01/2013 01:23 PM, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
>>> get_time is wrong function for getting tsc. You should create a timer
>>> event with 10000 units (=1 ms) and in its callback increase millisecond
>>> counter.
>> The problem is that such timer event would be machine-specific and
>> wouldn't work across different ARM SoCs. So the best place to handle
>> these machine-specific details would be in the platform firmware.
>> Unfortunately the EFI spec doesn't have a standard mechanism to retrieve
>> a timestamp counter, the most similar mechanism currently defined by the
>> spec is the get_time service.
> Looks at events in EFI spec. You can define a periodic event with 1ms
> period and custom function as callback. Then you just need to count in
> this function.

You are right, I wasn't aware of this capability. I have no idea how
widespread is support of timer events in different ARM EFI
implementations. We'll find out...

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