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Tue, 21 Jul 2020 14:19:24 -0700 (PDT) Subject: Re: [PATCH v2] iommu/mediatek: check 4GB mode by reading infracfg To: Yong Wu Cc: Miles Chen , Joerg Roedel , Rob Herring , iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, wsd_upstream@mediatek.com, Mike Rapoport , David Hildenbrand , Yingjoe Chen , Christoph Hellwig , Chao Hao References: <20200721021619.25575-1-miles.chen@mediatek.com> <1595330677.16172.55.camel@mhfsdcap03> From: Matthias Brugger Message-ID: <28bf052f-e388-d300-4abe-38f17bff01b6@gmail.com> Date: Tue, 21 Jul 2020 23:19:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <1595330677.16172.55.camel@mhfsdcap03> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 21/07/2020 13:24, Yong Wu wrote: > On Tue, 2020-07-21 at 11:40 +0200, Matthias Brugger wrote: >> >> On 21/07/2020 04:16, Miles Chen wrote: >>> In previous discussion [1] and [2], we found that it is risky to >>> use max_pfn or totalram_pages to tell if 4GB mode is enabled. >>> >>> Check 4GB mode by reading infracfg register, remove the usage >>> of the un-exported symbol max_pfn. >>> >>> This is a step towards building mtk_iommu as a kernel module. >>> >>> Change since v1: >>> 1. remove the phandle usage, search for infracfg instead [3] >>> 2. use infracfg instead of infracfg_regmap >>> 3. move infracfg definitaions to linux/soc/mediatek/infracfg.h >>> 4. update enable_4GB only when has_4gb_mode >>> >>> [1] https://lkml.org/lkml/2020/6/3/733 >>> [2] https://lkml.org/lkml/2020/6/4/136 >>> [3] https://lkml.org/lkml/2020/7/15/1147 >>> >>> Cc: Mike Rapoport >>> Cc: David Hildenbrand >>> Cc: Yong Wu >>> Cc: Yingjoe Chen >>> Cc: Christoph Hellwig >>> Cc: Yong Wu >>> Cc: Chao Hao >>> Cc: Rob Herring >>> Cc: Matthias Brugger >>> Signed-off-by: Miles Chen >>> --- >>> drivers/iommu/mtk_iommu.c | 26 +++++++++++++++++++++----- >>> include/linux/soc/mediatek/infracfg.h | 3 +++ >>> 2 files changed, 24 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c >>> index 2be96f1cdbd2..16765f532853 100644 >>> --- a/drivers/iommu/mtk_iommu.c >>> +++ b/drivers/iommu/mtk_iommu.c >>> @@ -3,7 +3,6 @@ >>> * Copyright (c) 2015-2016 MediaTek Inc. >>> * Author: Yong Wu >>> */ >>> -#include >>> #include >>> #include >>> #include >>> @@ -15,13 +14,16 @@ >>> #include >>> #include >>> #include >>> +#include >>> #include >>> #include >>> #include >>> #include >>> #include >>> +#include >>> #include >>> #include >>> +#include >>> #include >>> #include >>> >>> @@ -599,8 +601,10 @@ static int mtk_iommu_probe(struct platform_device *pdev) >>> struct resource *res; >>> resource_size_t ioaddr; >>> struct component_match *match = NULL; >>> + struct regmap *infracfg; >>> void *protect; >>> int i, larb_nr, ret; >>> + u32 val; >>> >>> data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); >>> if (!data) >>> @@ -614,10 +618,22 @@ static int mtk_iommu_probe(struct platform_device *pdev) >>> return -ENOMEM; >>> data->protect_base = ALIGN(virt_to_phys(protect), MTK_PROTECT_PA_ALIGN); >>> >>> - /* Whether the current dram is over 4GB */ >>> - data->enable_4GB = !!(max_pfn > (BIT_ULL(32) >> PAGE_SHIFT)); >>> - if (!data->plat_data->has_4gb_mode) >>> - data->enable_4GB = false; >>> + data->enable_4GB = false; >>> + if (data->plat_data->has_4gb_mode) { >>> + infracfg = syscon_regmap_lookup_by_compatible( >>> + "mediatek,mt8173-infracfg"); >>> + if (IS_ERR(infracfg)) { >>> + infracfg = syscon_regmap_lookup_by_compatible( >>> + "mediatek,mt2712-infracfg"); >>> + if (IS_ERR(infracfg)) >>> + return PTR_ERR(infracfg); >> >> I think we should check m4u_plat instead to decide which compatible we have to >> look for. >> Another option would be to add a general compatible something like >> "mtk-infracfg" and search for that. That would need an update of all DTS having >> a infracfg compatible right now. After thinking twice, this would break newer >> kernel with older device tree, so maybe it's better to go with m4u_plat switch >> statement. > > Add a "char *infracfg" in the plat_data, Use the mt2712, mt8173 > corresponding string in it. If it is NULL, It means the "enable_4GB" > always is false. Then we also can remove the flag "has_4gb_mode". > > is this OK? > It's an option, but I personally find that a bit hacky. Regards, Matthias