On Wed, 2020-07-15 at 23:05 +0200, Matthias Brugger wrote:

On 02/07/2020 11:37, Miles Chen wrote:

quoted

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://urldefense.com/v3/__https://lkml.org/lkml/2020/6/3/733__;!!CTRNKA9wMg0ARbw!16gAfVnSY87W4t5kE4iw20QPxBgS_SHBvPKlePKU7CGIb18nUzuRUjHumcf4oYVhIQ$ 
[2] https://urldefense.com/v3/__https://lkml.org/lkml/2020/6/4/136__;!!CTRNKA9wMg0ARbw!16gAfVnSY87W4t5kE4iw20QPxBgS_SHBvPKlePKU7CGIb18nUzuRUjHumcfr4i9p5g$ 

Cc: Mike Rapoport <redacted>
Cc: David Hildenbrand <redacted>
Cc: Yong Wu <yong.wu@mediatek.com>
Cc: Yingjoe Chen <redacted>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Miles Chen <redacted>
---
  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 <yong.wu@mediatek.com>
   */
-#include <linux/memblock.h>
  #include <linux/bug.h>
  #include <linux/clk.h>
  #include <linux/component.h>

@@ -15,11 +14,13 @@
  #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 <asm/barrier.h>

@@ -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.

Thanks for your comment.

ok. I'll do this in next version.

quoted

  #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.

ok. I'll do this in next version. 

quoted

  	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?

We have to error out in this case because the 4gb_mode setting must be
consistent with the h/w setting.

quoted

+		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.

ok. I'll do this in next version.

Miles

quoted

+	}
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	data->base = devm_ioremap_resource(dev, res);

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