[PATCH 8/9] ARM: pxa: add iwmmx support for PJ4

Eric Miao eric.y.miao at gmail.com
Wed Nov 10 14:15:47 EST 2010

2010/11/10 Haojian Zhuang <hzhuang1 at marvell.com>:
>>-----Original Message-----
>>From: Nicolas Pitre [mailto:nico at fluxnic.net]
>>Sent: 2010年11月10日 10:51 AM
>>To: Haojian Zhuang
>>Cc: Eric Miao; Haojian Zhuang; linux-arm-kernel; Zhou Zhu
>>Subject: Re: [PATCH 8/9] ARM: pxa: add iwmmx support for PJ4
>>On Tue, 9 Nov 2010, Haojian Zhuang wrote:
>>> On Tue, Nov 9, 2010 at 5:21 AM, Eric Miao <eric.y.miao at gmail.com> wrote:
>>> > On Mon, Nov 8, 2010 at 8:37 PM, Haojian Zhuang
>>> > <haojian.zhuang at marvell.com> wrote:
>>> >> From: Zhou Zhu <zzhu3 at marvell.com>
>>> >>
>>> >> iwmmx instructions are also used in PJ4. Add PJ4 support.
>>> >>
>>> >> Signed-off-by: Zhou Zhu <zzhu3 at marvell.com>
>>> >> Signed-off-by: Haojian Zhuang <haojian.zhuang at marvell.com>
>>> >> Cc: Eric Miao <eric.y.miao at gmail.com>
>>> > This isn't good. Have to figure out a clean way for this.
>>> >
>>> How about create new iwmmx.S and pj4-cp0.c? Since it can avoid macro.
>>Could you first explain why the CP15 reg number is different?  The
>>commit message for the proposed patch does not give any explanation for
>>the difference.
> Because PJ4 is different from XSC3. "cp 15.0.R15.c1.0" is used for specific control configuration.

I think PJ4 is more compliant with the ARMv7 spec, as XSC3 is doing
things a bit differently.

A run-time check of the core will be quicker, but doesn't look like a clean
solution. A better way to go maybe introducing different function entries
which call the common iwmmx handling code.

> Thanks
> Haojian

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