[PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Marek Szyprowski]

This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.

That patch broke IOMMU support for devices, which fails to probe for the
first time and use deferred probe approach. When non-NULL dma_ops is set
in arm_iommu_detach_device(), the given device later ignored by
arch_setup_dma_ops() and stays with non-IOMMU dma_ops.

Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 arch/arm/mm/dma-mapping.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 3c8534904209..5827a89b7de1 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1145,11 +1145,6 @@ int arm_dma_supported(struct device *dev, u64 mask)
 	return __dma_supported(dev, mask, false);
 }
 
-static const struct dma_map_ops *arm_get_dma_map_ops(bool coherent)
-{
-	return coherent ? &arm_coherent_dma_ops : &arm_dma_ops;
-}
-
 #ifdef CONFIG_ARM_DMA_USE_IOMMU
 
 static int __dma_info_to_prot(enum dma_data_direction dir, unsigned long attrs)
@@ -2294,7 +2289,7 @@ void arm_iommu_detach_device(struct device *dev)
 	iommu_detach_device(mapping->domain, dev);
 	kref_put(&mapping->kref, release_iommu_mapping);
 	to_dma_iommu_mapping(dev) = NULL;
-	set_dma_ops(dev, arm_get_dma_map_ops(dev->archdata.dma_coherent));
+	set_dma_ops(dev, NULL);
 
 	pr_debug("Detached IOMMU controller from %s device.\n", dev_name(dev));
 }
@@ -2355,6 +2350,11 @@ static void arm_teardown_iommu_dma_ops(struct device *dev) { }
 
 #endif	/* CONFIG_ARM_DMA_USE_IOMMU */
 
+static const struct dma_map_ops *arm_get_dma_map_ops(bool coherent)
+{
+	return coherent ? &arm_coherent_dma_ops : &arm_dma_ops;
+}
+
 void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 			const struct iommu_ops *iommu, bool coherent)
 {
-- 
2.17.1

[PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Marek Szyprowski]

This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.

That patch broke IOMMU support for devices, which fails to probe for the
first time and use deferred probe approach. When non-NULL dma_ops is set
in arm_iommu_detach_device(), the given device later ignored by
arch_setup_dma_ops() and stays with non-IOMMU dma_ops.

Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 arch/arm/mm/dma-mapping.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 3c8534904209..5827a89b7de1 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1145,11 +1145,6 @@ int arm_dma_supported(struct device *dev, u64 mask)
 	return __dma_supported(dev, mask, false);
 }
 
-static const struct dma_map_ops *arm_get_dma_map_ops(bool coherent)
-{
-	return coherent ? &arm_coherent_dma_ops : &arm_dma_ops;
-}
-
 #ifdef CONFIG_ARM_DMA_USE_IOMMU
 
 static int __dma_info_to_prot(enum dma_data_direction dir, unsigned long attrs)
@@ -2294,7 +2289,7 @@ void arm_iommu_detach_device(struct device *dev)
 	iommu_detach_device(mapping->domain, dev);
 	kref_put(&mapping->kref, release_iommu_mapping);
 	to_dma_iommu_mapping(dev) = NULL;
-	set_dma_ops(dev, arm_get_dma_map_ops(dev->archdata.dma_coherent));
+	set_dma_ops(dev, NULL);
 
 	pr_debug("Detached IOMMU controller from %s device.\n", dev_name(dev));
 }
@@ -2355,6 +2350,11 @@ static void arm_teardown_iommu_dma_ops(struct device *dev) { }
 
 #endif	/* CONFIG_ARM_DMA_USE_IOMMU */
 
+static const struct dma_map_ops *arm_get_dma_map_ops(bool coherent)
+{
+	return coherent ? &arm_coherent_dma_ops : &arm_dma_ops;
+}
+
 void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 			const struct iommu_ops *iommu, bool coherent)
 {
-- 
2.17.1


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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Thierry Reding]

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On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
> 
> That patch broke IOMMU support for devices, which fails to probe for the
> first time and use deferred probe approach. When non-NULL dma_ops is set
> in arm_iommu_detach_device(), the given device later ignored by
> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
> 
> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  arch/arm/mm/dma-mapping.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)

Can you point out exactly what drivers break because of this change? We
need to find a solution that works for everyone. Reverting is only
marginally useful because somebody will just end up wanting to revert
the revert because a different driver is now broken.

Thierry

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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Thierry Reding]

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On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
> 
> That patch broke IOMMU support for devices, which fails to probe for the
> first time and use deferred probe approach. When non-NULL dma_ops is set
> in arm_iommu_detach_device(), the given device later ignored by
> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
> 
> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  arch/arm/mm/dma-mapping.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)

Can you point out exactly what drivers break because of this change? We
need to find a solution that works for everyone. Reverting is only
marginally useful because somebody will just end up wanting to revert
the revert because a different driver is now broken.

Thierry

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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Thierry Reding]

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On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
> 
> That patch broke IOMMU support for devices, which fails to probe for the
> first time and use deferred probe approach. When non-NULL dma_ops is set
> in arm_iommu_detach_device(), the given device later ignored by
> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
> 
> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  arch/arm/mm/dma-mapping.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)

Can you point out exactly what drivers break because of this change? We
need to find a solution that works for everyone. Reverting is only
marginally useful because somebody will just end up wanting to revert
the revert because a different driver is now broken.

Thierry

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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Robin Murphy]

On 14/01/2019 16:09, Thierry Reding wrote:
> On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
>> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
>>
>> That patch broke IOMMU support for devices, which fails to probe for the
>> first time and use deferred probe approach. When non-NULL dma_ops is set
>> in arm_iommu_detach_device(), the given device later ignored by
>> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
>>
>> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
>> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> ---
>>   arch/arm/mm/dma-mapping.c | 12 ++++++------
>>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> Can you point out exactly what drivers break because of this change? We
> need to find a solution that works for everyone. Reverting is only
> marginally useful because somebody will just end up wanting to revert
> the revert because a different driver is now broken.

At first glance, it sounds like what we really want is for 
arch_teardown_iommu_ops() to completely clear any ops that 
arch_setup_dma_ops() installed - does the below suffice?

Robin.

----->8-----
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index f1e2922e447c..1e3e08a1c456 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
  		return;

  	arm_teardown_iommu_dma_ops(dev);
+	/* Let arch_setup_dma_ops() start again from scratch upon re-probe */
+	set_dma_ops(dev, NULL);
  }

Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Robin Murphy]

On 14/01/2019 16:09, Thierry Reding wrote:
> On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
>> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
>>
>> That patch broke IOMMU support for devices, which fails to probe for the
>> first time and use deferred probe approach. When non-NULL dma_ops is set
>> in arm_iommu_detach_device(), the given device later ignored by
>> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
>>
>> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
>> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> ---
>>   arch/arm/mm/dma-mapping.c | 12 ++++++------
>>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> Can you point out exactly what drivers break because of this change? We
> need to find a solution that works for everyone. Reverting is only
> marginally useful because somebody will just end up wanting to revert
> the revert because a different driver is now broken.

At first glance, it sounds like what we really want is for 
arch_teardown_iommu_ops() to completely clear any ops that 
arch_setup_dma_ops() installed - does the below suffice?

Robin.

----->8-----
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index f1e2922e447c..1e3e08a1c456 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
  		return;

  	arm_teardown_iommu_dma_ops(dev);
+	/* Let arch_setup_dma_ops() start again from scratch upon re-probe */
+	set_dma_ops(dev, NULL);
  }

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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Tobias Jakobi]

Hello everyone,

first of all thanks to Marek for looking into this.

@Robin: This works for me. The drivers now probe and bind correctly again.

With best wishes,
Tobias

Robin Murphy wrote:
> On 14/01/2019 16:09, Thierry Reding wrote:
>> On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
>>> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
>>>
>>> That patch broke IOMMU support for devices, which fails to probe for the
>>> first time and use deferred probe approach. When non-NULL dma_ops is set
>>> in arm_iommu_detach_device(), the given device later ignored by
>>> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
>>>
>>> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
>>> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in
>>> arm_iommu_detach_device()"
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> ---
>>>   arch/arm/mm/dma-mapping.c | 12 ++++++------
>>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> Can you point out exactly what drivers break because of this change? We
>> need to find a solution that works for everyone. Reverting is only
>> marginally useful because somebody will just end up wanting to revert
>> the revert because a different driver is now broken.
> 
> At first glance, it sounds like what we really want is for
> arch_teardown_iommu_ops() to completely clear any ops that arch_setup_dma_ops()
> installed - does the below suffice?
> 
> Robin.
> 
> ----->8-----
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f1e2922e447c..1e3e08a1c456 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
>          return;
> 
>      arm_teardown_iommu_dma_ops(dev);
> +    /* Let arch_setup_dma_ops() start again from scratch upon re-probe */
> +    set_dma_ops(dev, NULL);
>  }

Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Tobias Jakobi]

Hello everyone,

first of all thanks to Marek for looking into this.

@Robin: This works for me. The drivers now probe and bind correctly again.

With best wishes,
Tobias

Robin Murphy wrote:
> On 14/01/2019 16:09, Thierry Reding wrote:
>> On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
>>> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
>>>
>>> That patch broke IOMMU support for devices, which fails to probe for the
>>> first time and use deferred probe approach. When non-NULL dma_ops is set
>>> in arm_iommu_detach_device(), the given device later ignored by
>>> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
>>>
>>> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
>>> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in
>>> arm_iommu_detach_device()"
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> ---
>>>   arch/arm/mm/dma-mapping.c | 12 ++++++------
>>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> Can you point out exactly what drivers break because of this change? We
>> need to find a solution that works for everyone. Reverting is only
>> marginally useful because somebody will just end up wanting to revert
>> the revert because a different driver is now broken.
> 
> At first glance, it sounds like what we really want is for
> arch_teardown_iommu_ops() to completely clear any ops that arch_setup_dma_ops()
> installed - does the below suffice?
> 
> Robin.
> 
> ----->8-----
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f1e2922e447c..1e3e08a1c456 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
>          return;
> 
>      arm_teardown_iommu_dma_ops(dev);
> +    /* Let arch_setup_dma_ops() start again from scratch upon re-probe */
> +    set_dma_ops(dev, NULL);
>  }


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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Thierry Reding]

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On Mon, Jan 14, 2019 at 04:38:20PM +0000, Robin Murphy wrote:
> On 14/01/2019 16:09, Thierry Reding wrote:
> > On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
> > > This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
> > > 
> > > That patch broke IOMMU support for devices, which fails to probe for the
> > > first time and use deferred probe approach. When non-NULL dma_ops is set
> > > in arm_iommu_detach_device(), the given device later ignored by
> > > arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
> > > 
> > > Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
> > > Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
> > > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > > ---
> > >   arch/arm/mm/dma-mapping.c | 12 ++++++------
> > >   1 file changed, 6 insertions(+), 6 deletions(-)
> > 
> > Can you point out exactly what drivers break because of this change? We
> > need to find a solution that works for everyone. Reverting is only
> > marginally useful because somebody will just end up wanting to revert
> > the revert because a different driver is now broken.
> 
> At first glance, it sounds like what we really want is for
> arch_teardown_iommu_ops() to completely clear any ops that
> arch_setup_dma_ops() installed - does the below suffice?
> 
> Robin.
> 
> ----->8-----
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f1e2922e447c..1e3e08a1c456 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
>  		return;
> 
>  	arm_teardown_iommu_dma_ops(dev);
> +	/* Let arch_setup_dma_ops() start again from scratch upon re-probe */
> +	set_dma_ops(dev, NULL);
>  }

Seems to work fine on Tegra:

Tested-by: Thierry Reding <treding@nvidia.com>

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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Thierry Reding]

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On Mon, Jan 14, 2019 at 04:38:20PM +0000, Robin Murphy wrote:
> On 14/01/2019 16:09, Thierry Reding wrote:
> > On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
> > > This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
> > > 
> > > That patch broke IOMMU support for devices, which fails to probe for the
> > > first time and use deferred probe approach. When non-NULL dma_ops is set
> > > in arm_iommu_detach_device(), the given device later ignored by
> > > arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
> > > 
> > > Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
> > > Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
> > > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > > ---
> > >   arch/arm/mm/dma-mapping.c | 12 ++++++------
> > >   1 file changed, 6 insertions(+), 6 deletions(-)
> > 
> > Can you point out exactly what drivers break because of this change? We
> > need to find a solution that works for everyone. Reverting is only
> > marginally useful because somebody will just end up wanting to revert
> > the revert because a different driver is now broken.
> 
> At first glance, it sounds like what we really want is for
> arch_teardown_iommu_ops() to completely clear any ops that
> arch_setup_dma_ops() installed - does the below suffice?
> 
> Robin.
> 
> ----->8-----
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f1e2922e447c..1e3e08a1c456 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
>  		return;
> 
>  	arm_teardown_iommu_dma_ops(dev);
> +	/* Let arch_setup_dma_ops() start again from scratch upon re-probe */
> +	set_dma_ops(dev, NULL);
>  }

Seems to work fine on Tegra:

Tested-by: Thierry Reding <treding@nvidia.com>

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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Thierry Reding]

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On Mon, Jan 14, 2019 at 04:38:20PM +0000, Robin Murphy wrote:
> On 14/01/2019 16:09, Thierry Reding wrote:
> > On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
> > > This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
> > > 
> > > That patch broke IOMMU support for devices, which fails to probe for the
> > > first time and use deferred probe approach. When non-NULL dma_ops is set
> > > in arm_iommu_detach_device(), the given device later ignored by
> > > arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
> > > 
> > > Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
> > > Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"
> > > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > > ---
> > >   arch/arm/mm/dma-mapping.c | 12 ++++++------
> > >   1 file changed, 6 insertions(+), 6 deletions(-)
> > 
> > Can you point out exactly what drivers break because of this change? We
> > need to find a solution that works for everyone. Reverting is only
> > marginally useful because somebody will just end up wanting to revert
> > the revert because a different driver is now broken.
> 
> At first glance, it sounds like what we really want is for
> arch_teardown_iommu_ops() to completely clear any ops that
> arch_setup_dma_ops() installed - does the below suffice?
> 
> Robin.
> 
> ----->8-----
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f1e2922e447c..1e3e08a1c456 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
>  		return;
> 
>  	arm_teardown_iommu_dma_ops(dev);
> +	/* Let arch_setup_dma_ops() start again from scratch upon re-probe */
> +	set_dma_ops(dev, NULL);
>  }

Seems to work fine on Tegra:

Tested-by: Thierry Reding <treding@nvidia.com>

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Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Marek Szyprowski]

Hi Robin,

On 2019-01-14 17:38, Robin Murphy wrote:
> On 14/01/2019 16:09, Thierry Reding wrote:
>> On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
>>> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
>>>
>>> That patch broke IOMMU support for devices, which fails to probe for
>>> the
>>> first time and use deferred probe approach. When non-NULL dma_ops is
>>> set
>>> in arm_iommu_detach_device(), the given device later ignored by
>>> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
>>>
>>> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
>>> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in
>>> arm_iommu_detach_device()"
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> ---
>>>   arch/arm/mm/dma-mapping.c | 12 ++++++------
>>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> Can you point out exactly what drivers break because of this change? We
>> need to find a solution that works for everyone. Reverting is only
>> marginally useful because somebody will just end up wanting to revert
>> the revert because a different driver is now broken.
>
> At first glance, it sounds like what we really want is for
> arch_teardown_iommu_ops() to completely clear any ops that
> arch_setup_dma_ops() installed - does the below suffice?

I've initially also thought about similar fix, but then I found the
commit 1874619a7df4b14b23b14877e705ae15325773e3, which was the source of
this problem.

Robin: do you plan to send this fix as a complete patch or do you want
me to resend it with the above commit message and your's suggested-by?

>
> Robin.
>
> ----->8-----
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f1e2922e447c..1e3e08a1c456 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
>          return;
>
>      arm_teardown_iommu_dma_ops(dev);
> +    /* Let arch_setup_dma_ops() start again from scratch upon
> re-probe */
> +    set_dma_ops(dev, NULL);
>  }
>
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH] Revert "ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()"

[Marek Szyprowski]

Hi Robin,

On 2019-01-14 17:38, Robin Murphy wrote:
> On 14/01/2019 16:09, Thierry Reding wrote:
>> On Mon, Jan 14, 2019 at 02:22:40PM +0100, Marek Szyprowski wrote:
>>> This reverts commit 1874619a7df4b14b23b14877e705ae15325773e3.
>>>
>>> That patch broke IOMMU support for devices, which fails to probe for
>>> the
>>> first time and use deferred probe approach. When non-NULL dma_ops is
>>> set
>>> in arm_iommu_detach_device(), the given device later ignored by
>>> arch_setup_dma_ops() and stays with non-IOMMU dma_ops.
>>>
>>> Reported-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
>>> Fixes: 1874619a7df4 "ARM: dma-mapping: Set proper DMA ops in
>>> arm_iommu_detach_device()"
>>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> ---
>>>   arch/arm/mm/dma-mapping.c | 12 ++++++------
>>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> Can you point out exactly what drivers break because of this change? We
>> need to find a solution that works for everyone. Reverting is only
>> marginally useful because somebody will just end up wanting to revert
>> the revert because a different driver is now broken.
>
> At first glance, it sounds like what we really want is for
> arch_teardown_iommu_ops() to completely clear any ops that
> arch_setup_dma_ops() installed - does the below suffice?

I've initially also thought about similar fix, but then I found the
commit 1874619a7df4b14b23b14877e705ae15325773e3, which was the source of
this problem.

Robin: do you plan to send this fix as a complete patch or do you want
me to resend it with the above commit message and your's suggested-by?

>
> Robin.
>
> ----->8-----
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index f1e2922e447c..1e3e08a1c456 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -2390,4 +2390,6 @@ void arch_teardown_dma_ops(struct device *dev)
>          return;
>
>      arm_teardown_iommu_dma_ops(dev);
> +    /* Let arch_setup_dma_ops() start again from scratch upon
> re-probe */
> +    set_dma_ops(dev, NULL);
>  }
>
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland


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