Re: [PATCH v4 1/2] ARM: dma-mapping: Set proper DMA ops in arm_iommu_detach_device()

[Robin Murphy <robin.murphy@arm.com>]

On 30/05/18 15:06, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> Instead of setting the DMA ops pointer to NULL, set the correct,
> non-IOMMU ops depending on the device's coherency setting.

It looks like it's probably been 4 or 5 years since that became subtly 
wrong by virtue of the landscape changing around it, but it's clearly 
not enough of a problem to consider stable backports :)

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---
> Changes in v4:
> - new patch to fix existing arm_iommu_detach_device() to do what we need
> 
>   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 af27f1c22d93..87a0037574e4 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1151,6 +1151,11 @@ 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)
> @@ -2296,7 +2301,7 @@ 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, NULL);
> +	set_dma_ops(dev, arm_get_dma_map_ops(dev->archdata.dma_coherent));
>   
>   	pr_debug("Detached IOMMU controller from %s device.\n", dev_name(dev));
>   }
> @@ -2357,11 +2362,6 @@ 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)
>   {
> 
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