RE: [PATCH] ARM: Exynos4: integrate SYSMMU driver with DMA-mapping interface

[Marek Szyprowski <m.szyprowski@samsung.com>]

> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@arndb.de]
> Sent: Thursday, April 12, 2012 1:09 PM
> To: Marek Szyprowski
> Cc: 'Subash Patel'; linux-arm-kernel@lists.infradead.org; linaro-mm-sig@lists.linaro.org;
> linux-mm@kvack.org; linux-arch@vger.kernel.org; iommu@lists.linux-foundation.org; 'Kyungmin
> Park'; 'Joerg Roedel'; 'Russell King - ARM Linux'; 'Chunsang Jeong'; 'Krishna Reddy'; 'KyongHo
> Cho'; Andrzej Pietrasiewicz; 'Benjamin Herrenschmidt'; 'Konrad Rzeszutek Wilk'; 'Hiroshi Doyu'
> Subject: Re: [PATCH] ARM: Exynos4: integrate SYSMMU driver with DMA-mapping interface
> 
> On Thursday 12 April 2012, Marek Szyprowski wrote:
> > +
> > > > +/*
> > > > + * s5p_sysmmu_late_init
> > > > + * Create DMA-mapping IOMMU context for specified devices. This function must
> > > > + * be called later, once SYSMMU driver gets registered and probed.
> > > > + */
> > > > +static int __init s5p_sysmmu_late_init(void)
> > > > +{
> > > > +   platform_set_sysmmu(&SYSMMU_PLATDEV(fimc0).dev,&s5p_device_fimc0.dev);
> > > > +   platform_set_sysmmu(&SYSMMU_PLATDEV(fimc1).dev,&s5p_device_fimc1.dev);
> > > > +   platform_set_sysmmu(&SYSMMU_PLATDEV(fimc2).dev,&s5p_device_fimc2.dev);
> > > > +   platform_set_sysmmu(&SYSMMU_PLATDEV(fimc3).dev,&s5p_device_fimc3.dev);
> > > > +   platform_set_sysmmu(&SYSMMU_PLATDEV(mfc_l).dev,&s5p_device_mfc_l.dev);
> > > > +   platform_set_sysmmu(&SYSMMU_PLATDEV(mfc_r).dev,&s5p_device_mfc_r.dev);
> > > > +
> > > > +   s5p_create_iommu_mapping(&s5p_device_fimc0.dev, 0x20000000, SZ_128M, 4);
> > > > +   s5p_create_iommu_mapping(&s5p_device_fimc1.dev, 0x20000000, SZ_128M, 4);
> > > > +   s5p_create_iommu_mapping(&s5p_device_fimc2.dev, 0x20000000, SZ_128M, 4);
> > > > +   s5p_create_iommu_mapping(&s5p_device_fimc3.dev, 0x20000000, SZ_128M, 4);
> > > > +   s5p_create_iommu_mapping(&s5p_device_mfc_l.dev, 0x20000000, SZ_128M, 4);
> > > > +   s5p_create_iommu_mapping(&s5p_device_mfc_r.dev, 0x40000000, SZ_128M, 4);
> > > > +
> > > > +   return 0;
> > > > +}
> > > > +device_initcall(s5p_sysmmu_late_init);
> > >
> > > Shouldn't these things be specific to a SoC? With this RFC, it happens
> > > that you will predefine the IOMMU attachment and mapping information for
> > > devices in common location (dev-sysmmu.c)? This may lead to problems
> > > because there are some IP's with SYSMMU support in exynos5, but not
> > > available in exynos4 (eg: GSC, FIMC-LITE, FIMC-ISP) Previously we used
> > > to do above declaration in individual machine file, which I think was
> > > more meaningful.
> >
> > Right, I simplified the code too much. Keeping these definitions inside machine
> > files was a better idea. I completely forgot that Exynos sub-platform now covers
> > both Exynos4 and Exynos5 SoC families.
> 
> Ideally the information about iommu attachment should come from the
> device tree. We have the "dma-ranges" properties that define how a dma
> address space is mapped. I am not entirely sure how that works when you
> have multiple IOMMUs and if that requires defining addititional properties,
> but I think we should make it so that we don't have to hardcode specific
> devices in the source.

Right, until that time machine/board files are imho ok.

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center


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