linux-kernel - Re: [PATCH 2/4] ARM: mstar: Add machine for MStar infinity family SoCs

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Date:   Fri, 18 Oct 2019 06:15:15 +0900
From:   Daniel Palmer <daniel@...f.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/4] ARM: mstar: Add machine for MStar infinity family
 SoCs

On Thu, Oct 17, 2019 at 03:02:22PM +0200, Arnd Bergmann wrote:
> > I've moved this into infinity_barriers_init() using ioremap() as suggested.
> > I'd like to keep the fixed remap address for now as there are some
> > drivers in the vendor code that might be useful until rewrites are done but
> > are littered with hard coded addresses.
>
> Maybe keep the infinity_io_desc as an out-of-tree patch then? You can
> simply do both, and ioremap() will return the hardcoded address.

That makes sense.
 
> > I've taken the lock out and tested that the ethernet isn't sending garbage
> > and everything looks good.
> 
> I would not expect a missing spinlock to have an observable effect, the
> question is more whether it's correct in all rare corner cases where
> the barrier is interrupted and the interrupt handler uses another barrier.
> 
> I think it is, but I would recommend adding a comment to explain this if
> you drop the spinlock. (or a comment about why this works with fiq if you
> keep the lock).

I think I'll drop the lock for now and add it back if it becomes apparent
it's needed. I suspect it was added in the vendor code out of habit instead
of need.

Thanks for the input.

Daniel