Hi Marek,

Marek Szyprowski [off-list ref] wrote @ Mon, 24 Sep 2012 13:14:51 +0200:

Hello,

On Monday, September 24, 2012 11:45 AM Hiroshi Doyu wrote:

quoted

On Mon, 24 Sep 2012 11:28:01 +0200
James Bottomley [off-list ref] wrote:

quoted

On Mon, 2012-09-24 at 12:04 +0300, Hiroshi Doyu wrote:

quoted

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 at 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.

Thanks for the good info.