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Re: [Qemu-ppc] R128 interrupts


From: BALATON Zoltan
Subject: Re: [Qemu-ppc] R128 interrupts
Date: Thu, 15 Aug 2019 02:33:48 +0200 (CEST)
User-agent: Alpine 2.21.9999 (BSF 287 2018-06-16)

On Mon, 12 Aug 2019, Gerd Hoffmann wrote:
On Sun, Aug 11, 2019 at 04:36:18AM +0200, BALATON Zoltan wrote:
Now question is how to emulate this. Ideally this should be locked to the
host's VBlank so we avoid tearing which is the usual reason to use this
interrupt but we would need a way to get this on different platforms. On the
other hand the guest might expect this to happen at the frequency of the
mode it has programmed the card to which means that first we would need to
understand the clocking that we currently conveniently ignore to find out
the frequency and if that does not match the hosts mode we can't sync them.
Or for simplicity and a first version to try if it improves anything we
could ignore all this and just run a timer at 60Hz and generate VBlank
interrupt by that when enabled? Any better idea anyone? I'm not going to try
to implement this now so feel free to try if you want.

I'd start with a fixed frequency timer and refine later.

I've tried this (sent an RFC patch to the qemu-devel list: http://patchwork.ozlabs.org/patch/1147293/) but it does not seem to help the MacOS NDRV. It acknowledges the VBlank interrupts but just hangs polling for interrupt related regs (I think) way more frequently than should be necessary for VBlank so I'm not sure what it may be looking for now.

Regards,
BALATON Zoltan



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