From: Magnus Damm <magnus.damm@gmail.com>
To: linux-sh@vger.kernel.org
Subject: Re: qemu-sh CF access perormance
Date: Wed, 01 Apr 2009 04:22:07 +0000 [thread overview]
Message-ID: <aec7e5c30903312122s46ce25b4g8383cfa68e550dff@mail.gmail.com> (raw)
In-Reply-To: <49D2185C.4050909@juno.dti.ne.jp>
2009/3/31 Shin-ichiro KAWASAKI <kawasaki@juno.dti.ne.jp>:
> I'd like to ask following questions to linux-sh experts,
>
> - Why such io-traps are used to access CF?
> - Will this io-traps are used for SH7785LCR's SD card access?
>
> I guess these io-traps can be the reason why gcc takes so much time on qemu-sh.
The r2d hardware implements 16-bit only CF interface while driver
software requires 8-bit access. To work around this issue io_trapped
is used to convert 8-bit accesses to 16-bit accesses. This is quite
slow.
For more information, please see the comment in arch/sh/boards/mach-r2d/setup.c
To improve performance, consider adding a command line flag to the
kernel that disables io_trapped. This flag can then be set on the
kernel command line by the person running qemu.
Hope this helps!
Cheers,
/ magnus
next prev parent reply other threads:[~2009-04-01 4:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-31 13:19 qemu-sh CF access perormance Shin-ichiro KAWASAKI
2009-04-01 4:22 ` Magnus Damm [this message]
2009-04-01 15:25 ` Shin-ichiro KAWASAKI
2009-04-02 3:32 ` Paul Mundt
2009-04-02 14:36 ` Shin-ichiro KAWASAKI
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