Re: [PATCH v2] iommu/mediatek: check 4GB mode by reading infracfg

[Miles Chen]

On Tue, 2020-07-21 at 23:19 +0200, Matthias Brugger wrote:
> 
> 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://urldefense.com/v3/__https://lkml.org/lkml/2020/6/3/733__;!!CTRNKA9wMg0ARbw!w5YjY83YRL9_ijgXHwB1x2Dnb5BqiFUI8H5IAyAWWFMvUJKI9Qbj_zta2AaiFZejiQ$ 
> >>> [2] https://urldefense.com/v3/__https://lkml.org/lkml/2020/6/4/136__;!!CTRNKA9wMg0ARbw!w5YjY83YRL9_ijgXHwB1x2Dnb5BqiFUI8H5IAyAWWFMvUJKI9Qbj_zta2Aa9U2yQyg$ 
> >>> [3] https://urldefense.com/v3/__https://lkml.org/lkml/2020/7/15/1147__;!!CTRNKA9wMg0ARbw!w5YjY83YRL9_ijgXHwB1x2Dnb5BqiFUI8H5IAyAWWFMvUJKI9Qbj_zta2Aaxpk_Wjw$ 
> >>>
> >>> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> >>> Cc: David Hildenbrand <david@xxxxxxxxxx>
> >>> Cc: Yong Wu <yong.wu@xxxxxxxxxxxx>
> >>> Cc: Yingjoe Chen <yingjoe.chen@xxxxxxxxxxxx>
> >>> Cc: Christoph Hellwig <hch@xxxxxx>
> >>> Cc: Yong Wu <yong.wu@xxxxxxxxxxxx>
> >>> Cc: Chao Hao <chao.hao@xxxxxxxxxxxx>
> >>> Cc: Rob Herring <robh@xxxxxxxxxx>
> >>> Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
> >>> Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx>
> >>> ---
> >>>    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 <yong.wu@xxxxxxxxxxxx>
> >>>     */
> >>> -#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>
> >>>    
> >>> @@ -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.

Thanks Yong and Matthias for your comment.
I will try adding a char *infracfg in patch v3.


> 
> Regards,
> Matthias