From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751625AbcHYKYN (ORCPT ); Thu, 25 Aug 2016 06:24:13 -0400 Received: from mout.kundenserver.de ([217.72.192.75]:49539 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755749AbcHYKYK (ORCPT ); Thu, 25 Aug 2016 06:24:10 -0400 From: Arnd Bergmann To: Rich Felker Cc: Mark Rutland , Daniel Lezcano , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org, Rob Herring , Thomas Gleixner , Marc Zyngier Subject: Re: [PATCH v6 2/2] clocksource: add J-Core timer/clocksource driver Date: Thu, 25 Aug 2016 12:23:48 +0200 Message-ID: <1815946.6MSqSqog7A@wuerfel> User-Agent: KMail/5.1.3 (Linux/4.4.0-31-generic; KDE/5.18.0; x86_64; ; ) In-Reply-To: <3621664.0azN3a5cxy@wuerfel> References: <20160824214444.GZ15995@brightrain.aerifal.cx> <3621664.0azN3a5cxy@wuerfel> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:kNJNiNzj1FAMXKsDPBUZ4VWMGS1oCBf7ipzqC6CAuLh0Pk0o6dW Ndkenj4ZjhglKGFEDzKn/CzuWa9k2qDXoeh5/xfu0fF4luacUIo9mQOP6XCoF2vvM2nGRir VLOnsUPI8QQWpX4GRGNlnkTRNLvbjA4O7lXUTtDatsiOIz7XO6yXXpVvx87y5vJ0jG59WHH /PM3ds++MuP0oWZlP3oHA== X-UI-Out-Filterresults: notjunk:1;V01:K0:mLFgPfdgukk=:mTpejo+6Xvl682+eDnEPNW iWJ2FvqzELn1CgYKfR7IVtX45BgZ3YGlhkep4eMA2mPS6lfsfJ7RToF43thpYSJq+EuuPC+MS 4T85fL9EeXWoDbfTHI41DokRKlvThtT+W8LR9g+E/SCgtbuwutPI27lBreEd28G2E7qlywXZ9 h8n53w1nxsj4K6c1HjYIfkA9uD1WHIiX9xL2IZzbpv4HFOYnNryjiCzWRQeMjqq2ijTtyCcld ihYvcKqP4JzP5BHl+Y5cRhhqL6N2AWIw6BppvTe+ILPQsvjNKmcSS8HqK7uu1kZBgcs7Um4tT yEZxWE+/L1DEwiia4z/s8YTW6Z0E79GS0ku42uED1ylU+Hdn8C6kzQ5Rorxa+IM1e8vWrMhJM SevUOoQJucbPm2CIEB9wabxV8xNk3ir4eGN3nAFZBeAhHpIjLTu1ULgMzodt7TqKo0w3aDqgu wk0JhkcB2s7wckQ1G3mL9xtKLYPxgDkLa4iDsdHHmizAT3GCxfvq0ZaxQtclSJWmCrzTKUWFE zh7I8Bn314FYs+jiXxKeq7F+CxkUmb54f5w5HN+7ImE2QduqIyzIyKslgL+gyxQCa6lFKxNEa mD+fMBN98+OGWPAm2CUHLk4ZPNEhrxTlDI5JgzSFcs6EZlu5uVDsV3Ya0pIDF722PdPoTq5HK ps9fGesjf2Wj44lF+0xeBVWM4T97yxuV0p0RsNF+lUHgXPFx1fIE8ZusMt3bnuLiiA6OjdTUb 55sJSEDQpd8aXkyZ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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