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Fri, 16 Aug 2019 15:22:23 +0800 Message-ID: <1565940140.20346.21.camel@mhfsdcap03> Subject: Re: [PATCH v9 08/21] iommu/io-pgtable-arm-v7s: Extend MediaTek 4GB Mode From: Yong Wu To: Will Deacon Date: Fri, 16 Aug 2019 15:22:20 +0800 In-Reply-To: <20190815115021.7pbv5s2qbgsuitvh@willie-the-truck> References: <1565423901-17008-1-git-send-email-yong.wu@mediatek.com> <1565423901-17008-9-git-send-email-yong.wu@mediatek.com> <20190814144059.ruyc45yoqkwpbuga@willie-the-truck> <1565858869.12818.51.camel@mhfsdcap03> <20190815095123.rzgtpklvhtjlqir4@willie-the-truck> <1565864318.14278.4.camel@mhfsdcap03> <20190815115021.7pbv5s2qbgsuitvh@willie-the-truck> X-Mailer: Evolution 3.10.4-0ubuntu2 MIME-Version: 1.0 X-TM-SNTS-SMTP: BA349197A457FBABF294C6AEA76C731A816F8C5D8247B147DB51393DA440EAB42000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190816_002236_818585_FD12E9CD X-CRM114-Status: GOOD ( 26.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: youlin.pei@mediatek.com, devicetree@vger.kernel.org, Nicolas Boichat , cui.zhang@mediatek.com, srv_heupstream@mediatek.com, chao.hao@mediatek.com, Joerg Roedel , linux-kernel@vger.kernel.org, Evan Green , Tomasz Figa , iommu@lists.linux-foundation.org, Rob Herring , linux-mediatek@lists.infradead.org, Matthias Brugger , ming-fan.chen@mediatek.com, anan.sun@mediatek.com, Robin Murphy , Matthias Kaehlcke , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. > 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. > > 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?: 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. b) MTK code that apply the special "4gb mode" flow. And the "oas" will always is 34 bit since v7s has already supported our case. [1]http://lists.infradead.org/pipermail/linux-mediatek/2019-June/020991.html > > Thanks, > > Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel