From: Will Deacon <will@kernel.org>
To: Yong Wu <yong.wu@mediatek.com>
Cc: youlin.pei@mediatek.com, devicetree@vger.kernel.org,
Nicolas Boichat <drinkcat@chromium.org>,
cui.zhang@mediatek.com, srv_heupstream@mediatek.com,
chao.hao@mediatek.com, Joerg Roedel <joro@8bytes.org>,
linux-kernel@vger.kernel.org, Evan Green <evgreen@chromium.org>,
Tomasz Figa <tfiga@google.com>,
iommu@lists.linux-foundation.org,
Rob Herring <robh+dt@kernel.org>,
linux-mediatek@lists.infradead.org,
Matthias Brugger <matthias.bgg@gmail.com>,
ming-fan.chen@mediatek.com, anan.sun@mediatek.com,
Robin Murphy <robin.murphy@arm.com>,
Matthias Kaehlcke <mka@chromium.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v9 08/21] iommu/io-pgtable-arm-v7s: Extend MediaTek 4GB Mode
Date: Mon, 19 Aug 2019 12:24:38 +0100 [thread overview]
Message-ID: <20190819112438.fr233h5dgjkqb36r@willie-the-truck> (raw)
In-Reply-To: <1565940140.20346.21.camel@mhfsdcap03>
On Fri, Aug 16, 2019 at 03:22:20PM +0800, Yong Wu wrote:
> On Thu, 2019-08-15 at 12:50 +0100, Will Deacon wrote:
> > Ok, I think speaking to Robin helped me a bit with this...
> >
> > On Thu, Aug 15, 2019 at 06:18:38PM +0800, Yong Wu wrote:
> > > On Thu, 2019-08-15 at 10:51 +0100, Will Deacon wrote:
> > > > On Thu, Aug 15, 2019 at 04:47:49PM +0800, Yong Wu wrote:
> > > > > On Wed, 2019-08-14 at 15:41 +0100, Will Deacon wrote:
> > > > > > On Sat, Aug 10, 2019 at 03:58:08PM +0800, Yong Wu wrote:
> > > > > > > MediaTek extend the arm v7s descriptor to support the dram over 4GB.
> > > > > > >
> > > > > > > In the mt2712 and mt8173, it's called "4GB mode", the physical address
> > > > > > > is from 0x4000_0000 to 0x1_3fff_ffff, but from EMI point of view, it
> > > > > > > is remapped to high address from 0x1_0000_0000 to 0x1_ffff_ffff, the
> > > > > > > bit32 is always enabled. thus, in the M4U, we always enable the bit9
> > > > > > > for all PTEs which means to enable bit32 of physical address. Here is
> > > > > > > the detailed remap relationship in the "4GB mode":
> > > > > > > CPU PA -> HW PA
> > > > > > > 0x4000_0000 0x1_4000_0000 (Add bit32)
> > > > > > > 0x8000_0000 0x1_8000_0000 ...
> > > > > > > 0xc000_0000 0x1_c000_0000 ...
> > > > > > > 0x1_0000_0000 0x1_0000_0000 (No change)
> >
> > [...]
> >
> > > > > > The way I would like this quirk to work is that the io-pgtable code
> > > > > > basically sets bit 9 in the pte when bit 32 is set in the physical address,
> > > > > > and sets bit 4 in the pte when bit 33 is set in the physical address. It
> > > > > > would then do the opposite when converting a pte to a physical address.
> > > > > >
> > > > > > That way, your driver can call the page table code directly with the high
> > > > > > addresses and we don't have to do any manual offsetting or range checking
> > > > > > in the page table code.
> > > > >
> > > > > In this case, the mt8183 can work successfully while the "4gb
> > > > > mode"(mt8173/mt2712) can not.
> > > > >
> > > > > In the "4gb mode", As the remap relationship above, we should always add
> > > > > bit32 in pte as we did in [2]. and need add bit32 in the
> > > > > "iova_to_phys"(Not always add.). That means the "4gb mode" has a special
> > > > > flow:
> > > > > a. Always add bit32 in paddr_to_iopte.
> > > > > b. Add bit32 only when PA < 0x40000000 in iopte_to_paddr.
> > > >
> > > > I think this is probably at the heart of my misunderstanding. What is so
> > > > special about PAs (is this HW PA or CPU PA?) below 0x40000000? Is this RAM
> > > > or something else?
> > >
> > > SRAM and HW register that IOMMU can not access.
> >
> > Ok, so redrawing your table from above, I think we can say something like:
> >
> >
> > CPU Physical address
> > ====================
> >
> > 0G 1G 2G 3G 4G 5G
> > |---A---|---B---|---C---|---D---|---E---|
> > +--I/O--+------------Memory-------------+
> >
> >
> > IOMMU output physical address
> > =============================
> >
> > 4G 5G 6G 7G 8G
> > |---E---|---B---|---C---|---D---|
> > +------------Memory-------------+
> >
> >
> > Do you agree?
>
> Quite right.
Woohoo! So I finally got something right about this :) I'd be up for
including the diagrams above either in the commit message or in the IOMMU
driver code, along with a comment saying that region 'A' cannot be mapped
by the IOMMU and that the page-table walker uses CPU physical addresses.
> > If so, what happens to region 'A' (the I/O region) in the
> > IOMMU output physical address space. Is it accessible?
>
> No. IOMMU can not access region 'A' above.
Got it. Thanks.
> > Anyway, I think it's the job of the driver to convert between the two
> > address spaces, so that:
> >
> > - On ->map(), bit 32 of the CPU physical address is set before calling
> > into the iopgtable code
> >
> > - The result from ->iova_to_phys() should be the result from the
> > iopgtable code, but with the top bit cleared for addresses over
> > 5G.
> >
> > This assumes that:
> >
> > 1. We're ok setting bit 9 in the ptes mapping region 'E'.
> > 2. The IOMMU page-table walker uses CPU physical addresses
> >
> > Are those true?
>
> Yes. Then this patch would be close to the one[1] I sent in v8.
>
> Do I need to split this patch into 2 ones?:
Up to you. If you want to fix the current mainline behaviour of always
setting bit 4, then that should be a separate patch at the start of the
series which can be backported to stable. Is there a reason this doesn't go
wrong in practice?
> a).the pagetable code that support 34bit PA when MTK quirk is enabled.
> It only has the symmetric code handle BIT32/BIT33. Besides, I will add
> CONFIG_PHYS_ADDR_T_64BIT in the iopte_to_addr as commented before.
Hmm. I would prefer that the iopgtable code:
* Range checks the paddr against the oas in ->map()
* Refuses to accept an oas > 32 in ->alloc()
Then it's up to you whether you just want to pass an oas of 34 from the
IOMMU driver.
Will
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next prev parent reply other threads:[~2019-08-19 11:24 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-10 7:58 [PATCH v9 00/21] MT8183 IOMMU SUPPORT Yong Wu
2019-08-10 7:58 ` [PATCH v9 01/21] dt-bindings: mediatek: Add binding for mt8183 IOMMU and SMI Yong Wu
2019-08-10 7:58 ` [PATCH v9 02/21] iommu/mediatek: Use a struct as the platform data Yong Wu
2019-08-10 7:58 ` [PATCH v9 03/21] memory: mtk-smi: Use a general config_port interface Yong Wu
2019-08-10 7:58 ` [PATCH v9 04/21] memory: mtk-smi: Use a struct for the platform data for smi-common Yong Wu
2019-08-10 7:58 ` [PATCH v9 05/21] iommu/io-pgtable-arm-v7s: Add paddr_to_iopte and iopte_to_paddr helpers Yong Wu
2019-08-10 7:58 ` [PATCH v9 06/21] iommu/io-pgtable-arm-v7s: Use ias/oas to check the valid iova/pa Yong Wu
2019-08-10 7:58 ` [PATCH v9 07/21] iommu/io-pgtable-arm-v7s: Rename the quirk from MTK_4GB to MTK_EXT Yong Wu
2019-08-10 7:58 ` [PATCH v9 08/21] iommu/io-pgtable-arm-v7s: Extend MediaTek 4GB Mode Yong Wu
2019-08-14 14:41 ` Will Deacon
2019-08-15 8:47 ` Yong Wu
2019-08-15 9:51 ` Will Deacon
2019-08-15 10:03 ` Yong Wu
2019-08-15 10:04 ` Will Deacon
2019-08-15 10:18 ` Yong Wu
2019-08-15 11:50 ` Will Deacon
2019-08-16 7:22 ` Yong Wu
2019-08-19 11:24 ` Will Deacon [this message]
2019-08-10 7:58 ` [PATCH v9 09/21] iommu/mediatek: Add bclk can be supported optionally Yong Wu
2019-08-10 7:58 ` [PATCH v9 10/21] iommu/mediatek: Add larb-id remapped support Yong Wu
2019-08-10 7:58 ` [PATCH v9 11/21] iommu/mediatek: Refine protect memory definition Yong Wu
2019-08-10 7:58 ` [PATCH v9 12/21] iommu/mediatek: Move reset_axi into plat_data Yong Wu
2019-08-10 7:58 ` [PATCH v9 13/21] iommu/mediatek: Move vld_pa_rng " Yong Wu
2019-08-10 7:58 ` [PATCH v9 14/21] memory: mtk-smi: Add gals support Yong Wu
2019-08-10 7:58 ` [PATCH v9 15/21] iommu/mediatek: Add mt8183 IOMMU support Yong Wu
2019-08-10 7:58 ` [PATCH v9 16/21] iommu/mediatek: Add mmu1 support Yong Wu
2019-08-10 7:58 ` [PATCH v9 17/21] memory: mtk-smi: Invoke pm runtime_callback to enable clocks Yong Wu
2019-08-10 7:58 ` [PATCH v9 18/21] memory: mtk-smi: Add bus_sel for mt8183 Yong Wu
2019-08-10 7:58 ` [PATCH v9 19/21] iommu/mediatek: Fix VLD_PA_RNG register backup when suspend Yong Wu
2019-08-10 7:58 ` [PATCH v9 20/21] memory: mtk-smi: Get rid of need_larbid Yong Wu
2019-08-10 7:58 ` [PATCH v9 21/21] iommu/mediatek: Clean up struct mtk_smi_iommu Yong Wu
2019-08-14 8:18 ` [PATCH v9 00/21] MT8183 IOMMU SUPPORT Joerg Roedel
2019-08-14 8:24 ` Will Deacon
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