Re: [PATCH v2 03/04] iommu/ipmmu-vmsa: Break out 32-bit ARM mapping code

[Laurent Pinchart]

Hi Magnus,

Thank you for the patch.

On Tuesday 15 March 2016 13:22:04 Magnus Damm wrote:
> From: Magnus Damm <damm+renesas@xxxxxxxxxxxxx>
> 
> Make the driver compile on more than just 32-bit ARM
> by breaking out and wrapping ARM specific functions
> in #ifdefs. Not pretty, but needed to be able to use
> the driver on other architectures like ARM64.

Given that the callers of the new ARM-specific functions will, after patch 
"[PATCH 04/04] iommu/ipmmu-vmsa: Add new IOMMU_DOMAIN_DMA ops", be used only 
on !CONFIG_IOMMU_DMA, and that ARM64 selects CONFIG_IOMMU_DMA, wouldn't it 
make more sense not to extract the ARM-specific code in separate functions but 
compile-out the whole ipmmu_ops structure and all the related operation 
handlers when !CONFIG_IOMMU_DMA ?

I would order the patches as follows.

[PATCH v2 01/04] iommu/ipmmu-vmsa: Remove platform data handling
[PATCH v2 02/04] iommu/ipmmu-vmsa: Rework interrupt code and use bitmap for 
context
[PATCH v2 04/04] iommu/ipmmu-vmsa: Drop LPAE Kconfig dependency
[PATCH 02/04] iommu/ipmmu-vmsa: Break out utlb parsing code
[PATCH 03/04] iommu/ipmmu-vmsa: Break out domain allocation code

and then squash the following two patches, with conditional compilation for 
ipmmu_ops.

[PATCH 01/04] iommu/ipmmu-vmsa: 32-bit ARM may have CONFIG_IOMMU_DMA=y
[PATCH 04/04] iommu/ipmmu-vmsa: Add new IOMMU_DOMAIN_DMA ops

I think the result will be cleaner.

Please see below for a couple of other comments.

> Signed-off-by: Magnus Damm <damm+renesas@xxxxxxxxxxxxx>
> ---
> 
>  Changes since V1:
>  - Rebased to work without patch 2 and 3 from V1 series
> 
> drivers/iommu/ipmmu-vmsa.c |   94 +++++++++++++++++++++++++++-------------
> 1 file changed, 62 insertions(+), 32 deletions(-)
> 
> --- 0004/drivers/iommu/ipmmu-vmsa.c
> +++ work/drivers/iommu/ipmmu-vmsa.c	2016-03-15 12:25:45.040513000 +0900
> @@ -22,8 +22,10 @@
>  #include <linux/sizes.h>
>  #include <linux/slab.h>
> 
> +#ifdef CONFIG_ARM
>  #include <asm/dma-iommu.h>
>  #include <asm/pgalloc.h>
> +#endif
> 
>  #include "io-pgtable.h"
> 
> @@ -38,7 +40,9 @@ struct ipmmu_vmsa_device {
>  	DECLARE_BITMAP(ctx, IPMMU_CTX_MAX);
>  	struct ipmmu_vmsa_domain *domains[IPMMU_CTX_MAX];
> 
> +#ifdef CONFIG_ARM
>  	struct dma_iommu_mapping *mapping;
> +#endif
>  };
> 
>  struct ipmmu_vmsa_domain {
> @@ -615,6 +619,60 @@ static int ipmmu_find_utlbs(struct ipmmu
>  	return 0;
>  }
> 
> +#ifdef CONFIG_ARM
> +static int ipmmu_map_attach(struct device *dev, struct ipmmu_vmsa_device
> *mmu)
> +{
> +	int ret;
> +
> +	/*
> +	 * Create the ARM mapping, used by the ARM DMA mapping core to allocate
> +	 * VAs. This will allocate a corresponding IOMMU domain.
> +	 *
> +	 * TODO:
> +	 * - Create one mapping per context (TLB).
> +	 * - Make the mapping size configurable ? We currently use a 2GB mapping
> +	 *   at a 1GB offset to ensure that NULL VAs will fault.
> +	 */
> +	if (!mmu->mapping) {
> +		struct dma_iommu_mapping *mapping;
> +
> +		mapping = arm_iommu_create_mapping(&platform_bus_type,
> +						   SZ_1G, SZ_2G);
> +		if (IS_ERR(mapping)) {
> +			dev_err(mmu->dev, "failed to create ARM IOMMU mapping\n");
> +			return PTR_ERR(mapping);
> +		}
> +
> +		mmu->mapping = mapping;
> +	}
> +
> +	/* Attach the ARM VA mapping to the device. */
> +	ret = arm_iommu_attach_device(dev, mmu->mapping);
> +	if (ret < 0) {
> +		dev_err(dev, "Failed to attach device to VA mapping\n");
> +		arm_iommu_release_mapping(mmu->mapping);
> +	}
> +
> +	return ret;
> +}

How about adding a blank line here ?

> +static inline void ipmmu_detach(struct device *dev)
> +{
> +	arm_iommu_detach_device(dev);
> +}

And another one here ?

> +static inline void ipmmu_release_mapping(struct ipmmu_vmsa_device *mmu)
> +{
> +	arm_iommu_release_mapping(mmu->mapping);
> +}
> +#else
> +static inline int ipmmu_map_attach(struct device *dev,
> +				   struct ipmmu_vmsa_device *mmu)
> +{
> +	return 0;
> +}
> +static inline void ipmmu_detach(struct device *dev) {}
> +static inline void ipmmu_release_mapping(struct ipmmu_vmsa_device *mmu) {}

The compiler should be smart enough to inline all these functions if needed.

> +#endif
> +
>  static int ipmmu_add_device(struct device *dev)
>  {
>  	struct ipmmu_vmsa_archdata *archdata;
> @@ -695,41 +753,13 @@ static int ipmmu_add_device(struct devic
>  	archdata->num_utlbs = num_utlbs;
>  	dev->archdata.iommu = archdata;
> 
> -	/*
> -	 * Create the ARM mapping, used by the ARM DMA mapping core to allocate
> -	 * VAs. This will allocate a corresponding IOMMU domain.
> -	 *
> -	 * TODO:
> -	 * - Create one mapping per context (TLB).
> -	 * - Make the mapping size configurable ? We currently use a 2GB mapping
> -	 *   at a 1GB offset to ensure that NULL VAs will fault.
> -	 */
> -	if (!mmu->mapping) {
> -		struct dma_iommu_mapping *mapping;
> -
> -		mapping = arm_iommu_create_mapping(&platform_bus_type,
> -						   SZ_1G, SZ_2G);
> -		if (IS_ERR(mapping)) {
> -			dev_err(mmu->dev, "failed to create ARM IOMMU mapping\n");
> -			ret = PTR_ERR(mapping);
> -			goto error;
> -		}
> -
> -		mmu->mapping = mapping;
> -	}
> -
> -	/* Attach the ARM VA mapping to the device. */
> -	ret = arm_iommu_attach_device(dev, mmu->mapping);
> -	if (ret < 0) {
> -		dev_err(dev, "Failed to attach device to VA mapping\n");
> +	ret = ipmmu_map_attach(dev, mmu);
> +	if (ret < 0)
>  		goto error;
> -	}
> 
>  	return 0;
> 
>  error:
> -	arm_iommu_release_mapping(mmu->mapping);
> -
>  	kfree(dev->archdata.iommu);
>  	kfree(utlbs);
> 
> @@ -745,7 +775,7 @@ static void ipmmu_remove_device(struct d
>  {
>  	struct ipmmu_vmsa_archdata *archdata = dev->archdata.iommu;
> 
> -	arm_iommu_detach_device(dev);
> +	ipmmu_detach(dev);
>  	iommu_group_remove_device(dev);
> 
>  	kfree(archdata->utlbs);
> @@ -856,7 +886,7 @@ static int ipmmu_remove(struct platform_
>  	list_del(&mmu->list);
>  	spin_unlock(&ipmmu_devices_lock);
> 
> -	arm_iommu_release_mapping(mmu->mapping);
> +	ipmmu_release_mapping(mmu);
> 
>  	ipmmu_device_reset(mmu);

-- 
Regards,

Laurent Pinchart