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SubjectRe: [RFC PATCH 4/6] iommu/arm-smmu: Add support for IOMMU_DOMAIN_DMA in SMMUv1/SMMUv2 driver
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On 27/01/16 05:21, Anup Patel wrote:
> To allow use of large memory (> 4Gb) with 32bit devices we need to use
> some kind of iommu for such 32bit devices.
>
> This patch extends SMMUv1/SMMUv2 driver to support DMA domains which
> in-turn will allows us to use iommu based DMA mappings for 32bit devices.
>
> Signed-off-by: Anup Patel <anup.patel@broadcom.com>
> Reviewed-by: Ray Jui <rjui@broadcom.com>
> Reviewed-by: Scott Branden <sbranden@broadcom.com>
> ---
> drivers/iommu/arm-smmu.c | 21 ++++++++++++++++++++-
> 1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 9bdf6b2..43424fe 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -29,6 +29,7 @@
> #define pr_fmt(fmt) "arm-smmu: " fmt
>
> #include <linux/delay.h>
> +#include <linux/dma-iommu.h>
> #include <linux/dma-mapping.h>
> #include <linux/err.h>
> #include <linux/interrupt.h>
> @@ -967,7 +968,7 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
> {
> struct arm_smmu_domain *smmu_domain;
>
> - if (type != IOMMU_DOMAIN_UNMANAGED)
> + if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
> return NULL;
> /*
> * Allocate the domain and initialise some of its data structures.
> @@ -978,6 +979,12 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
> if (!smmu_domain)
> return NULL;
>
> + if (type == IOMMU_DOMAIN_DMA &&
> + iommu_get_dma_cookie(&smmu_domain->domain)) {
> + kfree(smmu_domain);
> + return NULL;
> + }
> +
> mutex_init(&smmu_domain->init_mutex);
> spin_lock_init(&smmu_domain->pgtbl_lock);
>
> @@ -992,6 +999,7 @@ static void arm_smmu_domain_free(struct iommu_domain *domain)
> * Free the domain resources. We assume that all devices have
> * already been detached.
> */
> + iommu_put_dma_cookie(domain);
> arm_smmu_destroy_domain_context(domain);
> kfree(smmu_domain);
> }
> @@ -1361,6 +1369,16 @@ static int arm_smmu_init_platform_device(struct device *dev,
> return 0;
> }
>
> +int arm_smmu_of_xlate(struct device *dev, struct of_phandle_args *args)
> +{
> + /*
> + * Nothing to do here because SMMU is already aware of all
> + * MMU masters and their stream IDs using mmu-master attibute
> + * SMMU DT node.
> + */

...but on the same hand this will also never get called if there's no
"iommus" property on the master. Maintaining support for existing users
of the "mmu-masters" binding is one thing (namely the thing that's been
slowing down my efforts to clean up the really hacky generic binding
support I did all the DMA stuff with), but having _both_ bindings in a
single DT is something I don't think anybody wants to see - is that how
you've tested this?

Robin.

> + return 0;
> +}
> +
> static int arm_smmu_add_device(struct device *dev)
> {
> struct iommu_group *group;
> @@ -1458,6 +1476,7 @@ static struct iommu_ops arm_smmu_ops = {
> .unmap = arm_smmu_unmap,
> .map_sg = default_iommu_map_sg,
> .iova_to_phys = arm_smmu_iova_to_phys,
> + .of_xlate = arm_smmu_of_xlate,
> .add_device = arm_smmu_add_device,
> .remove_device = arm_smmu_remove_device,
> .device_group = arm_smmu_device_group,
>

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