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From:   Vineet Gupta <vineet.gupta1@synopsys.com>
To:     Guenter Roeck <linux@roeck-us.net>
CC:     "linux-snps-arc@lists.infradead.org" 
        <linux-snps-arc@lists.infradead.org>,
        Eugeniy Paltsev <eugeniy.paltsev@synopsys.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Claudiu Zissulescu" <claudiu.zissulescu@synopsys.com>
Subject: Re: [PATCH] ARCv2: Add explcit unaligned access support (and
 ability to disable too)
Thread-Topic: [PATCH] ARCv2: Add explcit unaligned access support (and
 ability to disable too)
Thread-Index: AQHUz422b40bhmdW702O6EC/CP0bNQ==
Date:   Mon, 4 Mar 2019 22:32:00 +0000
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References: <20190228174742.GA18868@roeck-us.net>
 <C2D7FE5348E1B147BCA15975FBA2307501464380DE@US01WEMBX2.internal.synopsys.com>
 <20190228185929.GA9842@roeck-us.net>
 <C2D7FE5348E1B147BCA15975FBA2307501464381EE@US01WEMBX2.internal.synopsys.com>
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On 2/28/19 11:24 AM, Vineet Gupta wrote:=0A=
> On 2/28/19 10:59 AM, Guenter Roeck wrote:=0A=
>>> Once the patch hits mainline you could use that. In the mean time I'll =
back out=0A=
>>> the "detector" as it might trip other people too.=0A=
>>>=0A=
>> Can you possibly use $(cc-option,-mno-unaligned-access), or would that=
=0A=
>> defeat the purpose ?=0A=
>>=0A=
> Indeed I was looking into Kconfig documentation and found something simil=
ar.=0A=
> However there's an anti-dependency. It is enabled by default and can only=
 be=0A=
> disabled with $(cc-option,-mno-unaligned-access)=0A=
> So guess we will have to change  ARC_USE_UNALIGNED_MEM_ACCESS to=0A=
> ARC_*LACKS*_UNALIGNED_MEM_ACCESS=0A=
>=0A=
> I'll tinker a bit and post an update soon.=0A=
=0A=
I got around to testing a patch with inverted option, unaligned access is d=
efault=0A=
and ARC_UNALIGNED_ACCESS_NONE disables it. This option can depend on=0A=
$(cc-option,-mno-unaligned-access). The issue however is "broken" gcc silen=
tly=0A=
ignoring -mno-unaligned-access. So this option can't be auto disable with a=
ffected=0A=
gcc. So this approach won't work. The only way out is remove the stringent =
check=0A=
and just wait for upstream gcc to be fixed.=0A=
=0A=