linux-kernel - Re: [PATCH v3 11/24] iommu/io-pgtable-arm-v7s: Quad lvl1 pgtable for MediaTek

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Date:   Mon, 26 Oct 2020 15:41:23 +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>,
        "Krzysztof Kozlowski" <krzk@...nel.org>,
        Will Deacon <will@...nel.org>,
        Evan Green <evgreen@...omium.org>,
        Tomasz Figa <tfiga@...gle.com>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux-foundation.org>, <youlin.pei@...iatek.com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        <anan.sun@...iatek.com>, <chao.hao@...iatek.com>,
        <ming-fan.chen@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...gle.com>,
        <kernel-team@...roid.com>
Subject: Re: [PATCH v3 11/24] iommu/io-pgtable-arm-v7s: Quad lvl1 pgtable
 for MediaTek

On Fri, 2020-10-23 at 15:10 +0100, Robin Murphy wrote:
> On 2020-09-30 08:06, Yong Wu wrote:
> > The standard input iova bits is 32. MediaTek quad the lvl1 pagetable
> > (4 * lvl1). No change for lvl2 pagetable. Then the iova bits can reach
> > 34bit.
> > 
> > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > ---
> >   drivers/iommu/io-pgtable-arm-v7s.c | 13 ++++++++++---
> >   drivers/iommu/mtk_iommu.c          |  2 +-
> >   2 files changed, 11 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c
> > index 8362fdf76657..306bae2755ed 100644
> > --- a/drivers/iommu/io-pgtable-arm-v7s.c
> > +++ b/drivers/iommu/io-pgtable-arm-v7s.c
> > @@ -50,10 +50,17 @@
> >    */
> >   #define ARM_V7S_ADDR_BITS		32
> >   #define _ARM_V7S_LVL_BITS(lvl)		(16 - (lvl) * 4)
> > +/* MediaTek: totally 34bits, 14bits at lvl1 and 8bits at lvl2. */
> > +#define _ARM_V7S_LVL_BITS_MTK(lvl)	(20 - (lvl) * 6)
> 
> This should defined in terms of both lvl and cfg->ias. The formula here 
> is nothing more than a disgusting trick I made up since a linear 
> interpolation happened to fit the required numbers. That said, all of 
> these bits pretending that short-descriptor is a well-defined recursive 
> format only served to allow the rest of the code to look more like the 
> LPAE code - IIRC they've already diverged a fair bit since then, so 
> frankly a lot of this could stand to be unpicked and made considerably 
> clearer by simply accepting that level 1 and level 2 are different from 
> each other.

If the formula is not good and make it clearer, How about this?


/*
 * 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.
+*
+* MediaTek extend 2 bits to reach 34 bits, 14 bits at lvl1 and 8 bits
at lvl2.
 */

-#define _ARM_V7S_LVL_BITS(lvl)		(16 - (lvl) * 4)
+#define _ARM_V7S_LVL1_BITS_NR(cfg)     (((cfg)->ias == 32) ? 12 : 14)
+#define _ARM_V7S_LVL2_BITS_NR		8
+
+#define _ARM_V7S_LVL_BITS(lvl, cfg)    \
+      (((lvl) == 1) ? _ARM_V7S_LVL1_BITS_NR(cfg):_ARM_V7S_LVL2_BITS_NR)

> Robin.
> 
> >   #define ARM_V7S_LVL_SHIFT(lvl)		(ARM_V7S_ADDR_BITS - (4 + 8 * (lvl)))
> >   #define ARM_V7S_TABLE_SHIFT		10
> >   
> > -#define ARM_V7S_PTES_PER_LVL(lvl, cfg)	(1 << _ARM_V7S_LVL_BITS(lvl))
> > +#define ARM_V7S_PTES_PER_LVL(lvl, cfg)	({				\
> > +	int _lvl = lvl;							\
> > +	!arm_v7s_is_mtk_enabled(cfg) ?					\
> > +	 (1 << _ARM_V7S_LVL_BITS(_lvl)) : (1 << _ARM_V7S_LVL_BITS_MTK(_lvl));\
> > +})
> > +
> >   #define ARM_V7S_TABLE_SIZE(lvl, cfg)					\
> >   	(ARM_V7S_PTES_PER_LVL(lvl, cfg) * sizeof(arm_v7s_iopte))
> >   
> > @@ -63,7 +70,7 @@
> >   #define _ARM_V7S_IDX_MASK(lvl, cfg)	(ARM_V7S_PTES_PER_LVL(lvl, cfg) - 1)
> >   #define ARM_V7S_LVL_IDX(addr, lvl, cfg)	({			\
> >   	int _l = lvl;							\
> > -	((u32)(addr) >> ARM_V7S_LVL_SHIFT(_l)) & _ARM_V7S_IDX_MASK(_l, cfg); \
> > +	((addr) >> ARM_V7S_LVL_SHIFT(_l)) & _ARM_V7S_IDX_MASK(_l, cfg); \
> >   })
> >   
> >   /*
> > @@ -755,7 +762,7 @@ static struct io_pgtable *arm_v7s_alloc_pgtable(struct io_pgtable_cfg *cfg,
> >   {
> >   	struct arm_v7s_io_pgtable *data;
> >   
> > -	if (cfg->ias > ARM_V7S_ADDR_BITS)
> > +	if (cfg->ias > (arm_v7s_is_mtk_enabled(cfg) ? 34 : ARM_V7S_ADDR_BITS))
> >   		return NULL;
> >   
> >   	if (cfg->oas > (arm_v7s_is_mtk_enabled(cfg) ? 35 : ARM_V7S_ADDR_BITS))
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index f6a2e3eb59d2..6e85c9976a33 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -316,7 +316,7 @@ static int mtk_iommu_domain_finalise(struct mtk_iommu_domain *dom)
> >   			IO_PGTABLE_QUIRK_TLBI_ON_MAP |
> >   			IO_PGTABLE_QUIRK_ARM_MTK_EXT,
> >   		.pgsize_bitmap = mtk_iommu_ops.pgsize_bitmap,
> > -		.ias = 32,
> > +		.ias = 34,
> >   		.oas = 35,
> >   		.tlb = &mtk_iommu_flush_ops,
> >   		.iommu_dev = data->dev,
> >