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

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Date:	Wed, 28 Nov 2012 11:07:46 -0700
From:	Stephen Warren <swarren@...dotorg.org>
To:	Hiroshi Doyu <hdoyu@...dia.com>
CC:	"m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
	"joro@...tes.org" <joro@...tes.org>,
	"James.Bottomley@...senPartnership.com" 
	<James.Bottomley@...senPartnership.com>,
	"arnd@...db.de" <arnd@...db.de>, Krishna Reddy <vdumpa@...dia.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"minchan@...nel.org" <minchan@...nel.org>,
	"chunsang.jeong@...aro.org" <chunsang.jeong@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"subashrp@...il.com" <subashrp@...il.com>,
	"linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"kyungmin.park@...sung.com" <kyungmin.park@...sung.com>,
	"pullip.cho@...sung.com" <pullip.cho@...sung.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/1] ARM: tegra: bus_notifier registers IOMMU devices(was:
 How to specify IOMMU'able devices in DT)

On 11/28/2012 06:48 AM, Hiroshi Doyu wrote:
> Hiroshi Doyu <hdoyu@...dia.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@...dia.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@...dia.com>
> ---
>  arch/arm/mach-tegra/board-dt-tegra30.c |   40 ++++++++++++++++++++++++++++++++

Shouldn't this patch be to the IOMMU driver itself, not the core Tegra code?

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