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

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 <redacted>

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