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Time slowing down while doing IDE PIO transfer

To: linux-mips@linux-mips.org
Subject: Time slowing down while doing IDE PIO transfer
From: Maxime Bizon <mbizon@freebox.fr>
Date: Fri, 20 Jan 2006 18:26:37 +0100
Original-recipient: rfc822;linux-mips@linux-mips.org
Sender: linux-mips-bounce@linux-mips.org
Hello all,

I have a R4Kec board with an IDE controller, and run linux-mips 2.6.14
on it. When running a transfer on a cdrom drive, with dma disabled and
at lowest pio mode, time is slowing down (about 10 times too slow).

HZ is 1000, I'm using generic mips timer code (arch/mips/kernel/time.c),
HPT and timer interrupts are R4K.

This is I guess related to the interrupts being disabled during pio
transfer (I can't use unmaskirq btw).

Looking at timer_interrupt() code, I see that do_timer() will be only
called once, whether we have lost timer interrupts or not, I guess this
is the reason of this time problem. Is it a wanted behaviour ?

If this is the case, I guess my only hope is running with lower HZ or
using an RTC ?

Thanks,

-- 
Maxime

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