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Re: [Qemu-devel] Timer interrupts for -M raspi2

From: Andrew Baumann
Subject: Re: [Qemu-devel] Timer interrupts for -M raspi2
Date: Wed, 16 Mar 2016 23:14:10 +0000

Hi Antonio,

> From: Antonio Huete Jiménez [mailto:address@hidden
> Sent: Wednesday, 16 March 2016 3:40 PM
> Hi,
> I am experiencing what I think it's an issue with -M raspi2 and
> interrupts in a baremetal application.
> According to this document
> (https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2
> 836/QA7_rev3.4.pdf), and if I understood it correctly, you can enable timer
> interrupts for core0 by setting bit 0 at 0x40000040 and you can trigger them
> by using the ARM Generic
> Timer.
> With this procedure I can reliably trigger that timer interrupt in the
> real hardware by setting CNTP_CTL and CNTP_TVAL but on qemu it doesn't
> seem to be triggered.
> Can somebody please tell me what I might be doing wrong?

I don't think you're doing anything wrong; we just don't model this timer 
hardware yet (neither Linux nor Windows needs it). If you want to take a stab 
at adding it, the relevant hardware emulation is hw/intc/bcm2836_control.c.

If you're willing to use different timer sources, then I suggest looking at the 
ARM per-core timers. I also have Gregory's emulation code for the other bcm2835 
timers in my private github, and I hope to submit to upstream qemu after the 
current freeze, since it is needed for pi1 Linux support.


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