Messages in this thread | | | Date | Tue, 05 Feb 2013 19:42:09 +0900 (JST) | Subject | Re: [PATCH v6 1/4] iommu/shmobile: Add iommu driver for Renesas IPMMU modules | From | Hideki EIRAKU <> |
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Joerg Roedel,
From: Joerg Roedel <joro@8bytes.org> Subject: Re: [PATCH v6 1/4] iommu/shmobile: Add iommu driver for Renesas IPMMU modules Date: Fri, 1 Feb 2013 14:54:57 +0100
> 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?
I use dma_map_single() for flushing the page table to the IOMMU device. The dma_map_ops set by arch/arm/mm/dma-mapping.c are per-device (unlike the intel-iommu). The dma_* functions call into IOMMU drivers if the device is attached by arm_iommu_attach_device(), but I am using a NULL device here, so that shouldn't happen.
-- Hideki EIRAKU <hdk@igel.co.jp>
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