[PATCH 1/1] ARM: tegra: bus_notifier registers IOMMU devices(was: How to specify IOMMU'able devices in DT)

[Hiroshi Doyu]

Hiroshi Doyu <hdoyu at nvidia.com> wrote @ Mon, 24 Sep 2012 14:50:14 +0300 (EEST):
...
> > > > On Mon, 2012-09-24 at 12:04 +0300, Hiroshi Doyu wrote:
> > > > > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > > > > index a1a7225..9eae3be 100644
> > > > > --- a/drivers/base/platform.c
> > > > > +++ b/drivers/base/platform.c
> > > > > @@ -21,6 +21,8 @@
> > > > >  #include <linux/slab.h>
> > > > >  #include <linux/pm_runtime.h>
> > > > >
> > > > > +#include <asm/dma-iommu.h>
> > > > > +
> > > > >  #include "base.h"
> > > > >
> > > > >  #define to_platform_driver(drv)        (container_of((drv), struct
> > > > > platform_driver, \
> > > > > @@ -305,8 +307,19 @@ int platform_device_add(struct platform_device
> > > > > *pdev)
> > > > >                  dev_name(&pdev->dev), dev_name(pdev->dev.parent));
> > > > >
> > > > >         ret = device_add(&pdev->dev);
> > > > > -       if (ret == 0)
> > > > > -               return ret;
> > > > > +       if (ret)
> > > > > +               goto failed;
> > > > > +
> > > > > +#ifdef CONFIG_PLATFORM_ENABLE_IOMMU
> > > > > +       if (platform_bus_type.map && !pdev->dev.archdata.mapping) {
> > > > > +               ret = arm_iommu_attach_device(&pdev->dev,
> > > > > +                                             platform_bus_type.map);
> > > > > +               if (ret)
> > > > > +                       goto failed;
> > > >
> > > > This is horrible ... you're adding an architecture specific callback
> > > > into our generic code; that's really a no-no.  If the concept of
> > > > CONFIG_PLATFORM_ENABE_IOMMU is useful to more than just arm, then this
> > > > could become a generic callback.
> > > 
> > > As mentioned in the original, this is a heck to explain what is
> > > needed. I am looking for some generic solution for how to specify
> > > IOMMU info for each platform devices. I'm guessing that some other SoC
> > > may have the similar requirements on the above. As you mentioned, this
> > > solution should be a generic, not arch specific.
> > 
> > Please read more about bus notifiers. IMHO a good example is provided in 
> > the following thread:
> > http://www.mail-archive.com/linux-samsung-soc@vger.kernel.org/msg12238.html
> 
> This bus notifier seems enough flexible to afford the variation of
> IOMMU map info, like Tegra ASID, which could be platform-specific, and
> the other could be common too. There's already iommu_bus_notifier
> too. I'll try to implement something base on this.

Experimentally implemented as below. With the followig patch, each
device could specify its own map in DT, and automatically the device
would be attached to the map.

There is a case that some devices share a map. This patch doesn't
suppor such case yet.

>From 8cb75bb6f3a8535a077e0e85265f87c1f1289bfd Mon Sep 17 00:00:00 2001
From: Hiroshi Doyu <hdoyu at nvidia.com>
Date: Wed, 28 Nov 2012 14:47:04 +0200
Subject: [PATCH 1/1] ARM: tegra: bus_notifier registers IOMMU devices

platform_bus notifier registers IOMMU devices if dma-window is
specified.

Its format is:
  dma-window = <"start" "size">;
ex)
  dma-window = <0x12345000 0x8000>;

Signed-off-by: Hiroshi Doyu <hdoyu at nvidia.com>
---
 arch/arm/mach-tegra/board-dt-tegra30.c |   40 ++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/arch/arm/mach-tegra/board-dt-tegra30.c b/arch/arm/mach-tegra/board-dt-tegra30.c
index a2b6cf1..570d718 100644
--- a/arch/arm/mach-tegra/board-dt-tegra30.c
+++ b/arch/arm/mach-tegra/board-dt-tegra30.c
@@ -30,9 +30,11 @@
 #include <linux/of_fdt.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
+#include <linux/of_iommu.h>
 
 #include <asm/mach/arch.h>
 #include <asm/hardware/gic.h>
+#include <asm/dma-iommu.h>
 
 #include "board.h"
 #include "clock.h"
@@ -86,10 +88,48 @@ static __initdata struct tegra_clk_init_table tegra_dt_clk_init_table[] = {
 	{ NULL,		NULL,		0,		0},
 };
 
+#ifdef CONFIG_ARM_DMA_USE_IOMMU
+static int tegra_iommu_device_notifier(struct notifier_block *nb,
+				       unsigned long event, void *_dev)
+{
+	struct dma_iommu_mapping *map = NULL;
+	struct device *dev = _dev;
+	dma_addr_t base;
+	size_t size;
+	int err;
+
+	switch (event) {
+	case BUS_NOTIFY_ADD_DEVICE:
+		err = of_get_dma_window(dev->of_node, NULL, 0, NULL, &base,
+					&size);
+		if (!err)
+			map = arm_iommu_create_mapping(&platform_bus_type,
+						       base, size, 0);
+		if (IS_ERR_OR_NULL(map))
+			break;
+		if (arm_iommu_attach_device(dev, map))
+			dev_err(dev, "Failed to attach %s\n", dev_name(dev));
+		dev_dbg(dev, "Attached %s to map %p\n", dev_name(dev), map);
+		break;
+	}
+	return NOTIFY_DONE;
+}
+#else
+#define tegra_iommu_device_notifier NULL
+#endif
+
+static struct notifier_block tegra_iommu_device_nb = {
+	.notifier_call = tegra_iommu_device_notifier,
+};
+
 static void __init tegra30_dt_init(void)
 {
 	tegra_clk_init_from_table(tegra_dt_clk_init_table);
 
+	if (IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU))
+		bus_register_notifier(&platform_bus_type,
+				      &tegra_iommu_device_nb);
+
 	of_platform_populate(NULL, of_default_bus_match_table,
 				tegra30_auxdata_lookup, NULL);
 }
-- 
1.7.9.5