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Thu, 15 Aug 2019 18:03:33 +0800 Message-ID: <1565863410.12818.56.camel@mhfsdcap03> Subject: Re: [PATCH v9 08/21] iommu/io-pgtable-arm-v7s: Extend MediaTek 4GB Mode From: Yong Wu To: Will Deacon Date: Thu, 15 Aug 2019 18:03:30 +0800 In-Reply-To: <20190815095123.rzgtpklvhtjlqir4@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> X-Mailer: Evolution 3.10.4-0ubuntu2 MIME-Version: 1.0 X-TM-SNTS-SMTP: E5F8BB34E62DD0C8F592FA1695329834C7BBE85696305E63EF3B3ABA7868475D2000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190815_030352_488832_544ED4F6 X-CRM114-Status: GOOD ( 42.11 ) 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 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) > > > > > > So in this example, there are no PAs below 0x4000_0000 yet you later > > > add code to deal with that: > > > > > > > + /* Workaround for MTK 4GB Mode: Add BIT32 only when PA < 0x4000_0000.*/ > > > > + if (cfg->oas == ARM_V7S_MTK_4GB_OAS && paddr < 0x40000000UL) > > > > + paddr |= BIT_ULL(32); > > > > > > Why? Mainline currently doesn't do anything like this for the "4gb mode" > > > support as far as I can tell. In fact, we currently unconditionally set > > > bit 32 in the physical address returned by iova_to_phys() which wouldn't > > > match your CPU PAs listed above, so I'm confused about how this is supposed > > > to work. > > > > Actually current mainline have a bug for this. So I tried to use another > > special patch[1] for it in v8. > > If you're fixing a bug in mainline, I'd prefer to see that as a separate > patch. > > > But the issue is not critical since MediaTek multimedia consumer(v4l2 > > and drm) don't call iommu_iova_to_phys currently. > > > > > > > > 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 the HW registers. > > > > Please can you explain to me why the diff below doesn't work on top of > > > this series? > > > > The diff below is just I did in v8[3]. The different is that I move the > > "4gb mode" special flow in the mtk_iommu.c in v8, the code is like > > [4]below. When I sent v9, I found that I can distinguish the "4gb mode" > > with "oas == 33" in v7s. then I can "simply" add the 4gb special flow[5] > > based on your diff. > > > > > > > I'm happy to chat on IRC if you think it would be easier, > > > because I have a horrible feeling that we've been talking past each other > > > and I'd like to see this support merged for 5.4. > > > > Thanks very much for your view, I'm sorry that I don't have IRC. I will > > send the next version quickly if we have a conclusion here. Then Which > > way is better? If you'd like keep the pagetable code clean, I will add > > the "4gb mode" special flow into mtk_iommu.c. > > I mean, we could even talk on the phone if necessary because I can't accept > this code unless I understand how it works! > > To be blunt, I'd like to avoid the io-pgtable changes looking different to > what I suggested: > > > > diff --git a/drivers/iommu/io-pgtable-arm-v7s.c b/drivers/iommu/io-pgtable-arm-v7s.c > > > index ab12ef5f8b03..d8d84617c822 100644 > > > --- a/drivers/iommu/io-pgtable-arm-v7s.c > > > +++ b/drivers/iommu/io-pgtable-arm-v7s.c > > > @@ -184,7 +184,7 @@ static arm_v7s_iopte paddr_to_iopte(phys_addr_t paddr, int lvl, > > > arm_v7s_iopte pte = paddr & ARM_V7S_LVL_MASK(lvl); > > > > > > if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_EXT) { > > > - if ((paddr & BIT_ULL(32)) || cfg->oas == ARM_V7S_MTK_4GB_OAS) > > > + if (paddr & BIT_ULL(32)) > > > pte |= ARM_V7S_ATTR_MTK_PA_BIT32; > > > if (paddr & BIT_ULL(33)) > > > pte |= ARM_V7S_ATTR_MTK_PA_BIT33; > > > @@ -206,17 +206,14 @@ static phys_addr_t iopte_to_paddr(arm_v7s_iopte pte, int lvl, > > > mask = ARM_V7S_LVL_MASK(lvl); > > > > > > paddr = pte & mask; > > > - if (cfg->oas == 32 || !(cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_EXT)) > > > - return paddr; > > > > > > - if (pte & ARM_V7S_ATTR_MTK_PA_BIT33) > > > - paddr |= BIT_ULL(33); > > > + if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_EXT) { > > > + if (pte & ARM_V7S_ATTR_MTK_PA_BIT32) > > > + paddr |= BIT_ULL(32); > > > + if (pte & ARM_V7S_ATTR_MTK_PA_BIT33) > > > + paddr |= BIT_ULL(33); > > > + } > > > > > > - /* Workaround for MTK 4GB Mode: Add BIT32 only when PA < 0x4000_0000.*/ > > > - if (cfg->oas == ARM_V7S_MTK_4GB_OAS && paddr < 0x40000000UL) > > > - paddr |= BIT_ULL(32); > > > - else if (pte & ARM_V7S_ATTR_MTK_PA_BIT32) > > > - paddr |= BIT_ULL(32); > > > return paddr; > > > } > > so anything else should ideally go in the driver. The change above gives > the driver control over bits 4 and 9 in the pte, which I hope should be > sufficient. That said, yet another thing I don't understand is how the > IOMMU page table walker views physical addresses :/ Thanks the confirm. I will keep this way in the next version. > > Anyway, in your diff here... > > > [5]: > > ========================================================= > > diff --git a/drivers/iommu/io-pgtable-arm-v7s.c > > b/drivers/iommu/io-pgtable-arm-v7s.c > > index 78fd11e..8e974a5 100644 > > --- a/drivers/iommu/io-pgtable-arm-v7s.c > > +++ b/drivers/iommu/io-pgtable-arm-v7s.c > > @@ -184,7 +184,7 @@ static arm_v7s_iopte paddr_to_iopte(phys_addr_t > > paddr, int lvl, > > arm_v7s_iopte pte = paddr & ARM_V7S_LVL_MASK(lvl); > > > > if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_4GB) { > > - if (paddr & BIT_ULL(32)) > > + if (paddr & BIT_ULL(32) || cfg->oas == 33) > > pte |= ARM_V7S_ATTR_MTK_PA_BIT32; > > ... I'd like to drop the oas check, because the driver should be passing > in physical addresses with bit 32 set in this case, and... > > > if (paddr & BIT_ULL(33)) > > pte |= ARM_V7S_ATTR_MTK_PA_BIT33; > > @@ -207,7 +207,9 @@ static phys_addr_t iopte_to_paddr(arm_v7s_iopte pte, > > int lvl, > > > > paddr = pte & mask; > > if (cfg->quirks & IO_PGTABLE_QUIRK_ARM_MTK_4GB) { > > - if (pte & ARM_V7S_ATTR_MTK_PA_BIT32) > > + if (cfg->oas == 33 && paddr < 0x40000000UL) > > + paddr |= BIT_ULL(32); > > ... here I simply don't understand the significance of 0x40000000. > > Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel