linux-kernel - Re: [PATCH v4 17/24] iommu/mediatek: Add single domain

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Date:   Fri, 27 Nov 2020 14:21:32 +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>,
        Krzysztof Kozlowski <krzk@...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>,
        Greg Kroah-Hartman <gregkh@...gle.com>,
        <kernel-team@...roid.com>
Subject: Re: [PATCH v4 17/24] iommu/mediatek: Add single domain

On Thu, 2020-11-26 at 17:11 +0000, Robin Murphy wrote:
> On 2020-11-11 12:38, Yong Wu wrote:
> > Defaultly the iova range is 0-4G. here we add a single-domain(0-4G)
> > for the previous SoC. this also is a preparing patch for supporting
> > multi-domains.
> > 
> > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > ---
> >   drivers/iommu/mtk_iommu.c | 12 ++++++++++++
> >   1 file changed, 12 insertions(+)
> > 
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index bf3f4e0f4748..a7727a3899d1 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c
> > @@ -161,6 +161,10 @@ struct mtk_iommu_iova_region {
> >   	unsigned long long	size;
> >   };
> >   
> > +static const struct mtk_iommu_iova_region single_domain[] = {
> > +	{.iova_base = 0,		.size = SZ_4G},
> > +};
> 
> Hang on, given how the previous patch works, surely this means you're 
> now going to *reserve* the entire address space? That doesn't seem 
> right... :/

Could you help share more? in which case it is not right?

In the code:
domain->geometry.aperture_end = iova_base + size - 1. 

this is same with DMA_BIT_MASK(32). It looks don't change anything.

> 
> Robin.
> 
> > +
> >   /*
> >    * There may be 1 or 2 M4U HWs, But we always expect they are in the same domain
> >    * for the performance.
> > @@ -922,6 +926,8 @@ static const struct mtk_iommu_plat_data mt2712_data = {
> >   	.m4u_plat     = M4U_MT2712,
> >   	.flags        = HAS_4GB_MODE | HAS_BCLK | HAS_VLD_PA_RNG,
> >   	.inv_sel_reg  = REG_MMU_INV_SEL_GEN1,
> > +	.iova_region  = single_domain,
> > +	.iova_region_nr = ARRAY_SIZE(single_domain),
> >   	.larbid_remap = {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}},
> >   };
> >   
> > @@ -929,6 +935,8 @@ static const struct mtk_iommu_plat_data mt6779_data = {
> >   	.m4u_plat      = M4U_MT6779,
> >   	.flags         = HAS_SUB_COMM | OUT_ORDER_WR_EN | WR_THROT_EN,
> >   	.inv_sel_reg   = REG_MMU_INV_SEL_GEN2,
> > +	.iova_region   = single_domain,
> > +	.iova_region_nr = ARRAY_SIZE(single_domain),
> >   	.larbid_remap  = {{0}, {1}, {2}, {3}, {5}, {7, 8}, {10}, {9}},
> >   };
> >   
> > @@ -944,6 +952,8 @@ static const struct mtk_iommu_plat_data mt8173_data = {
> >   	.flags	      = HAS_4GB_MODE | HAS_BCLK | RESET_AXI |
> >   			HAS_LEGACY_IVRP_PADDR,
> >   	.inv_sel_reg  = REG_MMU_INV_SEL_GEN1,
> > +	.iova_region  = single_domain,
> > +	.iova_region_nr = ARRAY_SIZE(single_domain),
> >   	.larbid_remap = {{0}, {1}, {2}, {3}, {4}, {5}}, /* Linear mapping. */
> >   };
> >   
> > @@ -951,6 +961,8 @@ static const struct mtk_iommu_plat_data mt8183_data = {
> >   	.m4u_plat     = M4U_MT8183,
> >   	.flags        = RESET_AXI,
> >   	.inv_sel_reg  = REG_MMU_INV_SEL_GEN1,
> > +	.iova_region  = single_domain,
> > +	.iova_region_nr = ARRAY_SIZE(single_domain),
> >   	.larbid_remap = {{0}, {4}, {5}, {6}, {7}, {2}, {3}, {1}},
> >   };
> >   
> >