linux-kernel - Re: [PATCH v4 09/24] iommu/io-pgtable-arm-v7s: Clear LVL

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Date:   Fri, 27 Nov 2020 14:21:19 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Robin Murphy <robin.murphy@....com>
CC:     Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Will Deacon <will@...nel.org>, <youlin.pei@...iatek.com>,
        <devicetree@...r.kernel.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        <srv_heupstream@...iatek.com>, <chao.hao@...iatek.com>,
        <kernel-team@...roid.com>, <linux-kernel@...r.kernel.org>,
        Evan Green <evgreen@...omium.org>,
        "Tomasz Figa" <tfiga@...gle.com>,
        <iommu@...ts.linux-foundation.org>,
        <linux-mediatek@...ts.infradead.org>,
        Krzysztof Kozlowski <krzk@...nel.org>, <anan.sun@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...gle.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 09/24] iommu/io-pgtable-arm-v7s: Clear LVL_SHIFT/BITS
 macro instead of the formula

On Thu, 2020-11-26 at 16:03 +0000, Robin Murphy wrote:
> On 2020-11-11 12:38, Yong Wu wrote:
> > The current _ARM_V7S_LVL_BITS/ARM_V7S_LVL_SHIFT use a formula to calculate
> > the corresponding value for level1 and level2 to pretend the code sane.
> > Actually their level1 and level2 values are different from each other.
> > This patch only clear the two macro. No functional change.
> 
> Grammar nit: to "clear" the macro sounds like you're making it empty or 
> removing it entirely; I think you mean to say "clarify" here. English is 
> the worst language sometimes... :)

Thanks for the review. Feel free to tell me if some words is not fit:)

I will use "clarify" in the title.

> 
> Reviewed-by: Robin Murphy <robin.murphy@....com>
> 
> > Suggested-by: Robin Murphy <robin.murphy@....com>
> > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > ---
> >   drivers/iommu/io-pgtable-arm-v7s.c | 8 +++-----
> >   1 file changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> > index 4d0aa079470f..58cc201c10a3 100644
> > --- a/drivers/iommu/io-pgtable-arm-v7s.c
> > +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> > @@ -44,13 +44,11 @@
> >   
> >   /*
> >    * We have 32 bits total; 12 bits resolved at level 1, 8 bits at level 2,
> > - * and 12 bits in a page. With some carefully-chosen coefficients we can
> > - * hide the ugly inconsistencies behind these macros and at least let the
> > - * rest of the code pretend to be somewhat sane.
> > + * and 12 bits in a page.
> >    */
> >   #define ARM_V7S_ADDR_BITS		32
> > -#define _ARM_V7S_LVL_BITS(lvl)		(16 - (lvl) * 4)
> > -#define ARM_V7S_LVL_SHIFT(lvl)		(ARM_V7S_ADDR_BITS - (4 + 8 * (lvl)))
> > +#define _ARM_V7S_LVL_BITS(lvl)		((lvl) == 1 ? 12 : 8)
> > +#define ARM_V7S_LVL_SHIFT(lvl)		((lvl) == 1 ? 20 : 12)
> >   #define ARM_V7S_TABLE_SHIFT		10
> >   
> >   #define ARM_V7S_PTES_PER_LVL(lvl)	(1 << _ARM_V7S_LVL_BITS(lvl))
> >