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Re: [PATCH 1/2] powerpc/iommu: expose IOMMU page shift

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  Re: [PATCH 1/2] powerpc/iommu: expose IOMMU page shift David Gibson <david@gibson.dropbear.id.au> - 2015-10-06 05:30 +0200
    Re: [PATCH 1/2] powerpc/iommu: expose IOMMU page shift Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-12 18:10 +0200
      Re: [PATCH 1/2] powerpc/iommu: expose IOMMU page shift Nishanth Aravamudan <nacc@linux.vnet.ibm.com> - 2015-10-12 23:20 +0200

#1240138 — Re: [PATCH 1/2] powerpc/iommu: expose IOMMU page shift

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On Fri, Oct 02, 2015 at 10:18:00AM -0700, Nishanth Aravamudan wrote:
> We will leverage this macro in the NVMe driver, which needs to know the
> configured IOMMU page shift to properly configure its device's page
> size.
> 
> Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
> 
> ---
> Given this is available, it seems reasonable to expose -- and it doesn't
> really make sense to make the driver do a log2 call on the existing
> IOMMU_PAGE_SIZE() value.
> 
> diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> index ca18cff..6fdf857 100644
> --- a/arch/powerpc/include/asm/iommu.h
> +++ b/arch/powerpc/include/asm/iommu.h
> @@ -36,6 +36,7 @@
>  #define IOMMU_PAGE_MASK_4K       (~((1 << IOMMU_PAGE_SHIFT_4K) - 1))
>  #define IOMMU_PAGE_ALIGN_4K(addr) _ALIGN_UP(addr, IOMMU_PAGE_SIZE_4K)
>  
> +#define IOMMU_PAGE_SHIFT(tblptr) (tblptr)->it_page_shift
>  #define IOMMU_PAGE_SIZE(tblptr) (ASM_CONST(1) << (tblptr)->it_page_shift)

Seems like it would be a touch safer to alter IOMMU_PAGE_SIZE so it
uses the new IOMMU_PAGE_SHIFT macro.

>  #define IOMMU_PAGE_MASK(tblptr) (~((1 << (tblptr)->it_page_shift) - 1))
>  #define IOMMU_PAGE_ALIGN(addr, tblptr) _ALIGN_UP(addr, IOMMU_PAGE_SIZE(tblptr))
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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#1244859

On 06.10.2015 [14:19:43 +1100], David Gibson wrote:
> On Fri, Oct 02, 2015 at 10:18:00AM -0700, Nishanth Aravamudan wrote:
> > We will leverage this macro in the NVMe driver, which needs to know the
> > configured IOMMU page shift to properly configure its device's page
> > size.
> > 
> > Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
> > 
> > ---
> > Given this is available, it seems reasonable to expose -- and it doesn't
> > really make sense to make the driver do a log2 call on the existing
> > IOMMU_PAGE_SIZE() value.
> > 
> > diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> > index ca18cff..6fdf857 100644
> > --- a/arch/powerpc/include/asm/iommu.h
> > +++ b/arch/powerpc/include/asm/iommu.h
> > @@ -36,6 +36,7 @@
> >  #define IOMMU_PAGE_MASK_4K       (~((1 << IOMMU_PAGE_SHIFT_4K) - 1))
> >  #define IOMMU_PAGE_ALIGN_4K(addr) _ALIGN_UP(addr, IOMMU_PAGE_SIZE_4K)
> >  
> > +#define IOMMU_PAGE_SHIFT(tblptr) (tblptr)->it_page_shift
> >  #define IOMMU_PAGE_SIZE(tblptr) (ASM_CONST(1) << (tblptr)->it_page_shift)
> 
> Seems like it would be a touch safer to alter IOMMU_PAGE_SIZE so it
> uses the new IOMMU_PAGE_SHIFT macro.

Yes absolutely! Sorry, I initially didn't add the first macro, so didn't
think that through. Will update.

-Nish

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#1245148

On 12.10.2015 [09:03:52 -0700], Nishanth Aravamudan wrote:
> On 06.10.2015 [14:19:43 +1100], David Gibson wrote:
> > On Fri, Oct 02, 2015 at 10:18:00AM -0700, Nishanth Aravamudan wrote:
> > > We will leverage this macro in the NVMe driver, which needs to know the
> > > configured IOMMU page shift to properly configure its device's page
> > > size.
> > > 
> > > Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
> > > 
> > > ---
> > > Given this is available, it seems reasonable to expose -- and it doesn't
> > > really make sense to make the driver do a log2 call on the existing
> > > IOMMU_PAGE_SIZE() value.
> > > 
> > > diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
> > > index ca18cff..6fdf857 100644
> > > --- a/arch/powerpc/include/asm/iommu.h
> > > +++ b/arch/powerpc/include/asm/iommu.h
> > > @@ -36,6 +36,7 @@
> > >  #define IOMMU_PAGE_MASK_4K       (~((1 << IOMMU_PAGE_SHIFT_4K) - 1))
> > >  #define IOMMU_PAGE_ALIGN_4K(addr) _ALIGN_UP(addr, IOMMU_PAGE_SIZE_4K)
> > >  
> > > +#define IOMMU_PAGE_SHIFT(tblptr) (tblptr)->it_page_shift
> > >  #define IOMMU_PAGE_SIZE(tblptr) (ASM_CONST(1) << (tblptr)->it_page_shift)
> > 
> > Seems like it would be a touch safer to alter IOMMU_PAGE_SIZE so it
> > uses the new IOMMU_PAGE_SHIFT macro.
> 
> Yes absolutely! Sorry, I initially didn't add the first macro, so didn't
> think that through. Will update.

Err, replied too quickly -- just got back from vacation -- this is
from an old version of the patchset, we no longer introduce this macro.

-Nish

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