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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
 Denis Kirjanov <kda@linux-powerpc.org>
Cc: paulus@samba.org, mpe@ellerman.id.au, Michael Neuling <mikey@neuling.org>,
 linuxppc-dev@lists.ozlabs.org
Subject: Re: [RFC PATCH V1 14/33] powerpc/mm: Use helper for finding pte bits
 mapping I/O area
In-Reply-To: <1452657437.2403.17.camel@kernel.crashing.org>
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Date: Wed, 13 Jan 2016 11:37:57 +0530
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Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:

> On Tue, 2016-01-12 at 10:42 +0300, Denis Kirjanov wrote:
>> > +static inline unsigned long pte_io_cache_bits(void)
>> > +{
>> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0return _PAGE_NO_CACHE | _PAGE_GUARDED;
>> > +}
>> This could be just plain #define
>
> Or just use=C2=A0pgprot_noncached()
>
#define pgprot_noncached(prot)	  (__pgprot((pgprot_val(prot) & ~_PAGE_CACHE=
_CTL) | \
				            _PAGE_NO_CACHE | _PAGE_GUARDED))


That will return me a pgprot_t.  I can fix that by using
pgprot_val(pgprot_noncached(0)). Is that what you are suggesting ?

-aneesh