Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Sat, 25 Jan 2020 11:31:00 +0800
User-Agent: K-9 Mail for Android
In-Reply-To: <20200124140751.GA17030@alpha.franken.de>
References: <20200114122343.163685-1-jiaxun.yang@flygoat.com> <20200122184506.7zbzetn5xturxamj@pburton-laptop> <20200124140751.GA17030@alpha.franken.de>
MIME-Version: 1.0
Content-Type: text/plain;
 charset=utf-8
Content-Transfer-Encoding: quoted-printable
Subject: Re: [PATCH] MIPS: Introduce aligned IO memory operations
To:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Paul Burton <paulburton@kernel.org>
CC:     linux-mips@vger.kernel.org, chenhc@lemote.com,
        paul.burton@mips.com, linux-kernel@vger.kernel.org
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
Message-ID: <41DEDE07-DBA6-4397-A6F5-07D650436A6A@flygoat.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


=E4=BA=8E 2020=E5=B9=B41=E6=9C=8824=E6=97=A5 GMT+08:00 =E4=B8=8B=E5=8D=881=
0:07:51, Thomas Bogendoerfer <tsbogend@alpha=2Efranken=2Ede> =E5=86=99=E5=
=88=B0:
>On Wed, Jan 22, 2020 at 10:45:06AM -0800, Paul Burton wrote:
>> Hi Jiaxun,
>>=20
>> On Tue, Jan 14, 2020 at 08:23:43PM +0800, Jiaxun Yang wrote:
>> > Some platforms, such as Loongson64 or QEMU/KVM, don't support
>unaligned
>> > instructions like lwl or lwr in IO memory access=2E However, our
>current
>> > IO memcpy/memset is wired to the generic implementation, which
>leads
>> > to a fatal result=2E
>>=20
>> Hmm, I wonder if we should just do this unconditionally on all
>systems=2E
>> I can't think of a reason it'd ever be a good idea to use lwl/lwr on
>an
>> MMIO device=2E Any thoughts on that?
>
>depends on the type of device=2E I can see benefits for framebuffers
>and memory devices since memset/memcpy are more optimised than the
>function in this patch=2E

lwl/lwr is slower than this implementation on your system?
I thought that other platforms support unaligned request can be benefited =
from speed up of these instructions=2E

>
>Thomas=2E

--=20
Jiaxun Yang