Re: [PATCH v6 1/4] iommu/shmobile: Add iommu driver for Renesas IPMMU modules

Joerg Roedel
2013-02-01T13:55:02Z

On Mon, Jan 21, 2013 at 07:54:26PM +0900, Hideki EIRAKU wrote:
> This is the Renesas IPMMU driver and IOMMU API implementation.
>
> The IPMMU module supports the MMU function and the PMB function. The
> MMU function provides address translation by pagetable compatible with
> ARMv6. The PMB function provides address translation including
> tile-linear translation. This patch implements the MMU function.
>
> The iommu driver does not register a platform driver directly because:
> - the register space of the MMU function and the PMB function
> have a common register (used for settings flush), so they should ideally
> have a way to appropriately share this register.
> - the MMU function uses the IOMMU API while the PMB function does not.
> - the two functions may be used independently.
>
> Signed-off-by: Hideki EIRAKU <hdk@igel.co.jp>

The patch looks good in general. Just one question inline.

> +static int pgtable_alloc(struct shmobile_iommu_domain_pgtable *pgtable,
> + struct kmem_cache *cache, size_t size)
> +{
> + pgtable->pgtable = kmem_cache_zalloc(cache, GFP_ATOMIC);
> + if (!pgtable->pgtable)
> + return -ENOMEM;
> + pgtable->handle = dma_map_single(NULL, pgtable->pgtable, size,
> + DMA_TO_DEVICE);
> + return 0;
> +}

Why is it necessary to call dma_map_single() for IOMMU page-tables?
usually the dma_* functions call into IOMMU drivers, so why are they
used inside an IOMMU driver?

Regards,

Joerg