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

[Yong Wu]

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 <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?

> 
> Regards,
> Matthias
> 
> > +
> > +		}
> > +		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,
> >