linux-kernel - Re: Hungry for hardware timers

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Message-ID: <AANLkTimPU05Fs0VA4-u1aAxqv=AH+jNb+1S3OObXGNoD@mail.gmail.com>
Date:	Fri, 10 Dec 2010 10:17:51 +0530
From:	Jaswinder Singh <jaswinderlinux@...il.com>
To:	Clemens Ladisch <clemens@...isch.de>
Cc:	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Hungry for hardware timers

Hello,

On Tue, Sep 7, 2010 at 4:25 PM, Clemens Ladisch <clemens@...isch.de> wrote:
> Jaswinder Singh Rajput wrote:
>> As per dmesg([    0.325958] hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0)
>> so IRQs are like this :
>> HPET T0 : 2
>> HPET T1 : 8
>> HPET T2 : 0
>
> "0" means that the BIOS did not initialize it.  In this case, the driver
> will initializes it when accessed, with the first supported IRQ above 15.
> On your HPET's T2, this is IRQ 20.
>

I have used /dev/hpet as periodic interrupt and it works great but
settings for HPET_T2_CMP will be like this :

10 micro-seconds :  110 /* 0.00001 sec  */
100 micro-seconds : 1230 /* 0.0001 sec   */
1 milli-second : 13800 /* 0.001 sec    */
10 milli-seconds : 142580 /* 0.01 sec     */
100 milli-seconds : 1431150 /* 0.1 sec      */
1 second : 14317330 /* 1 sec        */
10 seconds : 143179330 /* 10 sec       */
100 seconds : 1431799400 /* 100 sec      */

I do not have a oscilloscope so I am measuring it by using printks.
I am curious, Why it is irregular.

I am looking for one more timer interrupt handler, how can I get one
more interrupt handler for user.

Thanks,
--
Jaswinder Singh.
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