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Wed, 15 Jul 2020 14:05:10 -0700 (PDT) Subject: Re: [PATCH 4/4] iommu/mediatek: check 4GB mode by reading infracfg To: Miles Chen , Joerg Roedel , Rob Herring Cc: iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com, Yong Wu , Chao Hao , Yingjoe Chen , Mike Rapoport , David Hildenbrand , Christoph Hellwig References: <20200702093721.6063-1-miles.chen@mediatek.com> <20200702093721.6063-4-miles.chen@mediatek.com> From: Matthias Brugger Message-ID: <84333997-735c-4a91-6d47-1dcb5c4a6078@gmail.com> Date: Wed, 15 Jul 2020 23:05:09 +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: <20200702093721.6063-4-miles.chen@mediatek.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 02/07/2020 11:37, Miles Chen wrote: > In previous disscusion [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 unexported symbol max_pfn. > > [1] https://lkml.org/lkml/2020/6/3/733 > [2] https://lkml.org/lkml/2020/6/4/136 > > Cc: Mike Rapoport > Cc: David Hildenbrand > Cc: Yong Wu > Cc: Yingjoe Chen > Cc: Christoph Hellwig > Signed-off-by: Miles Chen > --- > drivers/iommu/mtk_iommu.c | 22 ++++++++++++++++++---- > 1 file changed, 18 insertions(+), 4 deletions(-) > > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c > index 2be96f1cdbd2..09be57bd8d74 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 > @@ -15,11 +14,13 @@ > #include > #include > #include > +#include > #include > #include > #include > #include > #include > +#include > #include > #include > #include > @@ -91,6 +92,9 @@ > #define F_MMU_INT_ID_LARB_ID(a) (((a) >> 7) & 0x7) > #define F_MMU_INT_ID_PORT_ID(a) (((a) >> 2) & 0x1f) > > +#define REG_INFRA_MISC 0xf00 > +#define F_DDR_4GB_SUPPORT_EN BIT(13) > + As this is used for infracfg, I think it would be good to add it to include/linux/soc/mediatek/infracfg.h and include that file here. > #define MTK_PROTECT_PA_ALIGN 128 > > /* > @@ -599,8 +603,10 @@ static int mtk_iommu_probe(struct platform_device *pdev) > struct resource *res; > resource_size_t ioaddr; > struct component_match *match = NULL; > + struct regmap *infracfg_regmap; Maybe call it just infracfg. > void *protect; > int i, larb_nr, ret; > + u32 val; > > data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL); > if (!data) > @@ -614,10 +620,18 @@ 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) > + if (data->plat_data->has_4gb_mode) { > + infracfg_regmap = syscon_regmap_lookup_by_phandle(dev->of_node, > + "mediatek,infracfg"); > + if (IS_ERR(infracfg_regmap)) > + return PTR_ERR(infracfg_regmap); Do we need to error out, or could we be conservative and set endable_4GB = false? > + ret = regmap_read(infracfg_regmap, REG_INFRA_MISC, &val); > + if (ret) > + return ret; > + data->enable_4GB = !!(val & F_DDR_4GB_SUPPORT_EN); > + } else { > data->enable_4GB = false; Move that before the if() and update enable_4GB only in case of has_4gb_mode. > + } > > res = platform_get_resource(pdev, IORESOURCE_MEM, 0); > data->base = devm_ioremap_resource(dev, res); >