[PATCH 1/4] omap iommu: Check existence of arch_iommu

[PATCH 1/4] omap iommu: Check existence of arch_iommu

[Sakari Ailus]

Check that the arch_iommu has been installed before trying to use it. This
will lead to kernel oops if the arch_iommu isn't there.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
---
 arch/arm/plat-omap/iommu.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/arm/plat-omap/iommu.c b/arch/arm/plat-omap/iommu.c
index b1107c0..f0fea0b 100644
--- a/arch/arm/plat-omap/iommu.c
+++ b/arch/arm/plat-omap/iommu.c
@@ -104,6 +104,9 @@ static int iommu_enable(struct iommu *obj)
 	if (!obj)
 		return -EINVAL;
 
+	if (!arch_iommu)
+		return -ENOENT;
+
 	clk_enable(obj->clk);
 
 	err = arch_iommu->enable(obj);
-- 
1.7.2.3

Re: [PATCH 1/4] omap iommu: Check existence of arch_iommu

[Sakari Ailus]

Sakari Ailus wrote:
> Check that the arch_iommu has been installed before trying to use it. This
> will lead to kernel oops if the arch_iommu isn't there.

This was intended to go to linux-omap. Sorry for the noise.

-- 
Sakari Ailus
sakari.ailus@maxwell.research.nokia.com

RE: [PATCH 1/4] omap iommu: Check existence of arch_iommu

[Hiremath, Vaibhav]

> -----Original Message-----
> From: linux-media-owner@vger.kernel.org [mailto:linux-media-
> owner@vger.kernel.org] On Behalf Of Sakari Ailus
> Sent: Friday, March 25, 2011 8:43 PM
> To: linux-media@vger.kernel.org
> Cc: laurent.pinchart@ideasonboard.com; david.cohen@nokia.com;
> hiroshi.doyu@nokia.com
> Subject: [PATCH 1/4] omap iommu: Check existence of arch_iommu
> 
> Check that the arch_iommu has been installed before trying to use it. This
> will lead to kernel oops if the arch_iommu isn't there.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
> ---
>  arch/arm/plat-omap/iommu.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/plat-omap/iommu.c b/arch/arm/plat-omap/iommu.c
> index b1107c0..f0fea0b 100644
> --- a/arch/arm/plat-omap/iommu.c
> +++ b/arch/arm/plat-omap/iommu.c
> @@ -104,6 +104,9 @@ static int iommu_enable(struct iommu *obj)
>  	if (!obj)
>  		return -EINVAL;
> 
> +	if (!arch_iommu)
> +		return -ENOENT;
> +
[Hiremath, Vaibhav] Similar patch has already been submitted and accepted in community, not sure which baseline you are using. Please refer to below commit - 


commit ef4815ab1ff10d642c21ef92faa6544934bc78d1
Author: Martin Hostettler <martin@neutronstar.dyndns.org>
Date:   Thu Feb 24 12:51:31 2011 -0800

    omap: iommu: Gracefully fail iommu_enable if no arch_iommu is registered

    In a modular build of the iommu code it's possible that the arch iommu code
    isn't loaded when trying to enable the iommu. Instead of blindly following a
    null pointer return -NODEV in that case.

    Signed-off-by: Martin Hostettler <martin@neutronstar.dyndns.org>
    Signed-off-by: Tony Lindgren <tony@atomide.com>

diff --git a/arch/arm/plat-omap/iommu.c b/arch/arm/plat-omap/iommu.c
index b1107c0..3d8f55e 100644
--- a/arch/arm/plat-omap/iommu.c
+++ b/arch/arm/plat-omap/iommu.c
@@ -104,6 +104,9 @@ static int iommu_enable(struct iommu *obj)
        if (!obj)
                return -EINVAL;

+       if (!arch_iommu)
+               return -ENODEV;
+
        clk_enable(obj->clk);

        err = arch_iommu->enable(obj);


Thanks,
Vaibhav

>  	clk_enable(obj->clk);
> 
>  	err = arch_iommu->enable(obj);
> --
> 1.7.2.3
> 
> --
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Re: [PATCH 1/4] omap iommu: Check existence of arch_iommu

[Sakari Ailus]

Hiremath, Vaibhav wrote:
>> -----Original Message-----
>> From: linux-media-owner@vger.kernel.org [mailto:linux-media-
>> owner@vger.kernel.org] On Behalf Of Sakari Ailus
>> Sent: Friday, March 25, 2011 8:43 PM
>> To: linux-media@vger.kernel.org
>> Cc: laurent.pinchart@ideasonboard.com; david.cohen@nokia.com;
>> hiroshi.doyu@nokia.com
>> Subject: [PATCH 1/4] omap iommu: Check existence of arch_iommu
>>
>> Check that the arch_iommu has been installed before trying to use it. This
>> will lead to kernel oops if the arch_iommu isn't there.
>>
>> Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
>> ---
>>  arch/arm/plat-omap/iommu.c |    3 +++
>>  1 files changed, 3 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/arm/plat-omap/iommu.c b/arch/arm/plat-omap/iommu.c
>> index b1107c0..f0fea0b 100644
>> --- a/arch/arm/plat-omap/iommu.c
>> +++ b/arch/arm/plat-omap/iommu.c
>> @@ -104,6 +104,9 @@ static int iommu_enable(struct iommu *obj)
>>  	if (!obj)
>>  		return -EINVAL;
>>
>> +	if (!arch_iommu)
>> +		return -ENOENT;
>> +
> [Hiremath, Vaibhav] Similar patch has already been submitted and
accepted in community, not sure which baseline you are using. Please
refer to below commit -
> 

Thanks, Vaibhav. I guess I need to update my tree and resend the set...

Cheers,

-- 
Sakari Ailus
sakari.ailus@maxwell.research.nokia.com

[PATCH 2/4] omap iommu: Add module information to struct iommu_functions

[Sakari Ailus]

Whichever module that implements the struct, may not be unloaded while it's
in use.  Prepare to this by adding module reference to the structure.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
---
 arch/arm/plat-omap/include/plat/iommu.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/arm/plat-omap/include/plat/iommu.h b/arch/arm/plat-omap/include/plat/iommu.h
index 69230d6..26fefb4 100644
--- a/arch/arm/plat-omap/include/plat/iommu.h
+++ b/arch/arm/plat-omap/include/plat/iommu.h
@@ -79,6 +79,7 @@ struct iotlb_lock {
 /* architecture specific functions */
 struct iommu_functions {
 	unsigned long	version;
+	struct module *module;
 
 	int (*enable)(struct iommu *obj);
 	void (*disable)(struct iommu *obj);
-- 
1.7.2.3

[PATCH 3/4] omap2 iommu: Set module information in omap2_iommu_ops

[Sakari Ailus]

Set omap2_iommu_ops.module to point to THIS_MODULE.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
---
 arch/arm/mach-omap2/iommu2.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-omap2/iommu2.c b/arch/arm/mach-omap2/iommu2.c
index 14ee686..cf0c32a 100644
--- a/arch/arm/mach-omap2/iommu2.c
+++ b/arch/arm/mach-omap2/iommu2.c
@@ -342,6 +342,8 @@ static const struct iommu_functions omap2_iommu_ops = {
 	.save_ctx	= omap2_iommu_save_ctx,
 	.restore_ctx	= omap2_iommu_restore_ctx,
 	.dump_ctx	= omap2_iommu_dump_ctx,
+
+	.module		= THIS_MODULE,
 };
 
 static int __init omap2_iommu_init(void)
-- 
1.7.2.3

[PATCH 4/4] omap iommu: Prevent iommu implementations from being unloaded while in use

[Sakari Ailus]

Prevent module implementing arch_iommu from being unloaded while the
arch_iommu is in use, essentially while the iommu has been acquired using
iommu_get() by increasing module use count.

This assumes that the arch_iommu has to be uninstalled at module unload
time.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
---
 arch/arm/plat-omap/iommu.c |   31 +++++++++++++++++++++++++++++--
 1 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/arch/arm/plat-omap/iommu.c b/arch/arm/plat-omap/iommu.c
index f0fea0b..430ed94 100644
--- a/arch/arm/plat-omap/iommu.c
+++ b/arch/arm/plat-omap/iommu.c
@@ -35,6 +35,7 @@ static const struct iommu_functions *arch_iommu;
 
 static struct platform_driver omap_iommu_driver;
 static struct kmem_cache *iopte_cachep;
+static struct mutex arch_iommu_mutex;
 
 /**
  * install_iommu_arch - Install archtecure specific iommu functions
@@ -45,10 +46,17 @@ static struct kmem_cache *iopte_cachep;
  **/
 int install_iommu_arch(const struct iommu_functions *ops)
 {
-	if (arch_iommu)
+	mutex_lock(&arch_iommu_mutex);
+
+	if (arch_iommu) {
+		mutex_unlock(&arch_iommu_mutex);
 		return -EBUSY;
+	}
 
 	arch_iommu = ops;
+
+	mutex_unlock(&arch_iommu_mutex);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(install_iommu_arch);
@@ -58,13 +66,22 @@ EXPORT_SYMBOL_GPL(install_iommu_arch);
  * @ops:	a pointer to architecture specific iommu functions
  *
  * This interface uninstalls the iommu algorighm installed previously.
+ *
+ * Note: This function may only be called at module_exit() function of
+ * a module which implements arch_iommu. Otherwise another mechanism
+ * from the module use count only to ensure the arch_iommu stays there
+ * has to be implemented.
  **/
 void uninstall_iommu_arch(const struct iommu_functions *ops)
 {
+	mutex_lock(&arch_iommu_mutex);
+
 	if (arch_iommu != ops)
 		pr_err("%s: not your arch\n", __func__);
 
 	arch_iommu = NULL;
+
+	mutex_unlock(&arch_iommu_mutex);
 }
 EXPORT_SYMBOL_GPL(uninstall_iommu_arch);
 
@@ -104,14 +121,20 @@ static int iommu_enable(struct iommu *obj)
 	if (!obj)
 		return -EINVAL;
 
-	if (!arch_iommu)
+	mutex_lock(&arch_iommu_mutex);
+	if (!arch_iommu || !try_module_get(arch_iommu->module)) {
+		mutex_unlock(&arch_iommu_mutex);
 		return -ENOENT;
+	}
 
 	clk_enable(obj->clk);
 
 	err = arch_iommu->enable(obj);
 
 	clk_disable(obj->clk);
+
+	mutex_unlock(&arch_iommu_mutex);
+
 	return err;
 }
 
@@ -125,6 +148,8 @@ static void iommu_disable(struct iommu *obj)
 	arch_iommu->disable(obj);
 
 	clk_disable(obj->clk);
+
+	module_put(arch_iommu->module);
 }
 
 /*
@@ -1058,6 +1083,8 @@ static int __init omap_iommu_init(void)
 		return -ENOMEM;
 	iopte_cachep = p;
 
+	mutex_init(&arch_iommu_mutex);
+
 	return platform_driver_register(&omap_iommu_driver);
 }
 module_init(omap_iommu_init);
-- 
1.7.2.3