linux-kernel - Re: [PATCH] MIPS: smp-mt: enable all hardware interrupts on second VPE

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Message-ID: <20220707100630.GC9894@alpha.franken.de>
Date:   Thu, 7 Jul 2022 12:06:30 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Marc Zyngier <maz@...nel.org>,
        Sander Vanheule <sander@...nheule.net>,
        Aleksander Jan Bajkowski <olek2@...pl>,
        Hauke Mehrtens <hauke@...ke-m.de>, git@...ger-koblitz.de,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: smp-mt: enable all hardware interrupts on second
 VPE

On Wed, Jul 06, 2022 at 11:56:47AM +0200, Martin Blumenstingl wrote:
> Without this patch all interrupts are fine on VPE 0 and with SMP disabled.

I fully understand the problem. But not everybody uses this interrupt
setup, so changing generic code will have effects there too.

> - why can MIPS CPU interrupt 6 and 7 be enabled unconditionally while
> 2-5 cannot be enabled unconditionally?

7 is timer interrupt and is usually wired for 34K cpus and 6 is
performance counter hopefully handled as well. And I agree that
this still isn't the best approach here

> - seeing that there's also a mips_gic_present() check in the opposite
> case of what Aleksander's patch modifies: does this indicate that
> unmasking CPU interrupt lines for VPE 1 is not handled by the MIPS CPU
> interrupt controller driver at all at this point (and if so: do you
> have any suggestions how to properly fix this)?

I haven't checked how GIC is integrated. Iirc it does something similair
to Lantiq's irq controller and hides all CPU internal interrupts behind
it.

So I see two solutions for your problem.

1. Add "mti,cpu-interrupt-controller" to the DT and wire it up
2. Create your own struct plat_smp_ops using vsmp_smp_ops as
   a template and overload .boot_secondary

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]