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Subject: Re: [RESEND PATCH v4] iommu/mediatek: check 4GB mode by reading
 infracfg
To:     Yong Wu <yong.wu@mediatek.com>,
        Miles Chen <miles.chen@mediatek.com>
Cc:     Rob Herring <robh@kernel.org>, wsd_upstream@mediatek.com,
        David Hildenbrand <david@redhat.com>,
        Joerg Roedel <joro@8bytes.org>, linux-kernel@vger.kernel.org,
        Mike Rapoport <rppt@linux.ibm.com>,
        iommu@lists.linux-foundation.org,
        linux-mediatek@lists.infradead.org,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Yingjoe Chen <yingjoe.chen@mediatek.com>,
        Christoph Hellwig <hch@lst.de>,
        linux-arm-kernel@lists.infradead.org
References: <20200826085618.2889-1-miles.chen@mediatek.com>
 <1598506280.19851.5.camel@mhfsdcap03>
From:   Robin Murphy <robin.murphy@arm.com>
Message-ID: <e34db4dc-49a6-d414-e438-b528703ffb80@arm.com>
Date:   Thu, 27 Aug 2020 20:27:47 +0100
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On 2020-08-27 06:31, Yong Wu wrote:
> On Wed, 2020-08-26 at 16:56 +0800, 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.
>>
>> [1] https://lore.kernel.org/lkml/20200603161132.2441-1-miles.chen@mediatek.com/
>> [2] https://lore.kernel.org/lkml/20200604080120.2628-1-miles.chen@mediatek.com/
>> [3] https://lore.kernel.org/lkml/20200715205120.GA778876@bogus/
>>
>> Cc: Mike Rapoport <rppt@linux.ibm.com>
>> Cc: David Hildenbrand <david@redhat.com>
>> Cc: Yong Wu <yong.wu@mediatek.com>
>> Cc: Yingjoe Chen <yingjoe.chen@mediatek.com>
>> Cc: Christoph Hellwig <hch@lst.de>
>> Cc: Rob Herring <robh@kernel.org>
>> Cc: Matthias Brugger <matthias.bgg@gmail.com>
>> Signed-off-by: Miles Chen <miles.chen@mediatek.com>
>>
>> ---
>>
>> Change since v3
>> - use lore.kernel.org links
>> - move "change since..." after "---"
>>
>> Change since v2:
>> - determine compatible string by m4u_plat
>> - rebase to next-20200720
>> - add "---"
>>
>> Change since v1:
>> - remove the phandle usage, search for infracfg instead [3]
>> - use infracfg instead of infracfg_regmap
>> - move infracfg definitaions to linux/soc/mediatek/infracfg.h
>> - update enable_4GB only when has_4gb_mode
>> ---
>>   drivers/iommu/mtk_iommu.c             | 34 +++++++++++++++++++++++----
>>   include/linux/soc/mediatek/infracfg.h |  3 +++
>>   2 files changed, 32 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
>> index 785b228d39a6..adc350150492 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 <yong.wu@mediatek.com>
>>    */
>> -#include <linux/memblock.h>
>>   #include <linux/bug.h>
>>   #include <linux/clk.h>
>>   #include <linux/component.h>
>> @@ -15,13 +14,16 @@
>>   #include <linux/iommu.h>
>>   #include <linux/iopoll.h>
>>   #include <linux/list.h>
>> +#include <linux/mfd/syscon.h>
>>   #include <linux/of_address.h>
>>   #include <linux/of_iommu.h>
>>   #include <linux/of_irq.h>
>>   #include <linux/of_platform.h>
>>   #include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>>   #include <linux/slab.h>
>>   #include <linux/spinlock.h>
>> +#include <linux/soc/mediatek/infracfg.h>
>>   #include <asm/barrier.h>
>>   #include <soc/mediatek/smi.h>
>>   
>> @@ -640,8 +642,11 @@ 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;
>> +	char                    *p;
>>   
>>   	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>>   	if (!data)
>> @@ -655,10 +660,29 @@ 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 (!MTK_IOMMU_HAS_FLAG(data->plat_data, HAS_4GB_MODE))
>> -		data->enable_4GB = false;
>> +	data->enable_4GB = false;

Nit: this isn't really necessary, since the structure is kzalloc()ed.

>> +	if (MTK_IOMMU_HAS_FLAG(data->plat_data, HAS_4GB_MODE)) {
>> +		switch (data->plat_data->m4u_plat) {
>> +		case M4U_MT2712:
>> +			p = "mediatek,mt2712-infracfg";
>> +			break;
>> +		case M4U_MT8173:
>> +			p = "mediatek,mt8173-infracfg";
>> +			break;
>> +		default:
>> +			p = NULL;
>> +		}
>> +
> 
> This can be simplified:
> 
>          if (data->plat_data->m4u_plat == M4U_MT2712)
> 		p = "mediatek,mt2712-infracfg";
> 	else if(data->plat_data->m4u_plat == M4U_MT8173)
> 		p = "mediatek,mt8173-infracfg";
> 	else
> 		return -EINVAL;

Right, at this point the HAS_4GB_MODE flag is entirely redundant and 
should be removed. FWIW I still think your suggestion of putting the 
infracfg names into plat_data would be even better and cleaner - there's 
plenty of precedent for that sort of thing (see "git grep '\.clk_name'" 
for example).

Robin.

> 
> Then,
> Reviewed-by: Yong Wu <yong.wu@mediatek.com>
> 	
> 
>> +		infracfg = syscon_regmap_lookup_by_compatible(p);
>> +
>> +		if (IS_ERR(infracfg))
>> +			return PTR_ERR(infracfg);
>> +
>> +		ret = regmap_read(infracfg, REG_INFRA_MISC, &val);
>> +		if (ret)
>> +			return ret;
>> +		data->enable_4GB = !!(val & F_DDR_4GB_SUPPORT_EN);
>> +	}
>>   
>>   	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>   	data->base = devm_ioremap_resource(dev, res);
>> diff --git a/include/linux/soc/mediatek/infracfg.h b/include/linux/soc/mediatek/infracfg.h
>> index fd25f0148566..233463d789c6 100644
>> --- a/include/linux/soc/mediatek/infracfg.h
>> +++ b/include/linux/soc/mediatek/infracfg.h
>> @@ -32,6 +32,9 @@
>>   #define MT7622_TOP_AXI_PROT_EN_WB		(BIT(2) | BIT(6) | \
>>   						 BIT(7) | BIT(8))
>>   
>> +#define REG_INFRA_MISC				0xf00
>> +#define F_DDR_4GB_SUPPORT_EN			BIT(13)
>> +
>>   int mtk_infracfg_set_bus_protection(struct regmap *infracfg, u32 mask,
>>   		bool reg_update);
>>   int mtk_infracfg_clear_bus_protection(struct regmap *infracfg, u32 mask,
> 
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