From: Arnd Bergmann <arnd@arndb.de>
To: Rich Felker <dalias@libc.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-sh@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Marc Zyngier <Marc.Zyngier@arm.com>
Subject: Re: [PATCH v6 2/2] clocksource: add J-Core timer/clocksource driver
Date: Thu, 25 Aug 2016 12:23:48 +0200 [thread overview]
Message-ID: <1815946.6MSqSqog7A@wuerfel> (raw)
In-Reply-To: <3621664.0azN3a5cxy@wuerfel>
On Wednesday, August 24, 2016 11:57:08 PM CEST Arnd Bergmann wrote:
> > I'm not familiar with those classifications, but from what I can tell,
> > BE32 describes it correctly. I'll see if I can get someone to verify
> > this. Is there a reason it's not widely used anymore? Perhaps
> > something related to supporting misaligned word-sized loads/stores?
>
> The main problem I see is that you can't easily use MMIO registers that
> are not 32-bit wide -- you end up having to flip not just the register
> contents but also the lower bits of the address in order to reach
> the right contents of the register.
>
Actually there is a much more serious problem with BE32/LE32 mode:
doing unaligned access to RAM is a huge pain at the HW level,
and also when emulating it in the kernel on CPUs that require
aligned access. In ARM THUMB2 mode, you can even have unaligned
32-bit instructions.
Arnd
next prev parent reply other threads:[~2016-08-25 10:23 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-04 4:30 [PATCH v6 0/2] J-Core timer support Rich Felker
[not found] ` <cover.147018b3518.git.dalias-8zAoT0mYgF4@public.gmane.org>
2016-08-04 4:30 ` [PATCH v6 2/2] clocksource: add J-Core timer/clocksource driver Rich Felker
2016-08-04 8:24 ` Alexnader Kuleshov
2016-08-04 19:42 ` Rich Felker
2016-08-24 16:42 ` Daniel Lezcano
2016-08-24 17:40 ` Rich Felker
[not found] ` <20160824174001.GW15995-C3MtFaGISjmo6RMmaWD+6Sb1p8zYI1N1@public.gmane.org>
2016-08-24 19:01 ` Marc Zyngier
2016-08-24 19:20 ` Rich Felker
[not found] ` <20160824192009.GX15995-C3MtFaGISjmo6RMmaWD+6Sb1p8zYI1N1@public.gmane.org>
2016-08-24 22:21 ` Mark Rutland
2016-08-24 20:01 ` Arnd Bergmann
2016-08-24 20:52 ` Rich Felker
2016-08-24 21:22 ` Mark Rutland
2016-08-24 21:44 ` Rich Felker
2016-08-24 21:57 ` Arnd Bergmann
2016-08-25 10:23 ` Arnd Bergmann [this message]
2016-08-24 22:54 ` Mark Rutland
2016-08-25 8:07 ` Thomas Gleixner
2016-08-25 14:56 ` Rich Felker
2016-08-25 15:41 ` Thomas Gleixner
2016-08-25 17:45 ` Rich Felker
2016-08-25 16:38 ` Mark Rutland
2016-08-25 17:51 ` Rich Felker
2016-08-25 18:21 ` Mark Rutland
2016-08-25 19:20 ` Rich Felker
2016-08-26 9:04 ` Daniel Lezcano
2016-08-04 4:30 ` [PATCH v6 1/2] of: add J-Core timer bindings Rich Felker
[not found] ` <5e1d4f3346f69bdd9d840c8b5a855c1f93ff93f6.147018b3518.git.dalias-8zAoT0mYgF4@public.gmane.org>
2016-08-04 18:16 ` Rob Herring
-- strict thread matches above, loose matches on Subject: below --
2016-08-03 0:18 [PATCH v6 0/2] J-Core timer support Rich Felker
[not found] ` <cover.1470183518.git.dalias-8zAoT0mYgF4@public.gmane.org>
2016-03-17 23:12 ` [PATCH v6 2/2] clocksource: add J-Core timer/clocksource driver Rich Felker
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