On Tue, 10 Jul 2012 10:14:01 +0200 markz <markz@xxxxxxxxxx> wrote: > On Mon, 2012-07-09 at 23:28 +0800, Hiroshi Doyu wrote: > > Hi Mark, adding linux-tegra on Cc:.... > > > > Mark Zhang <markz@xxxxxxxxxx> wrote @ Mon, 9 Jul 2012 14:13:13 +0200: > > > > > > Hi Mark, Cc: Thierry & Ken, > > > > > > > > Can GEM allow DRM to use contigious memory? That could be easier. > > > > > > > > Otherwise, I think that you need to make drv->dev iommu'able before > > > > calling DMA API if you want to use IOMMU. To make drv->dev iommu'able, > > > > you need to call arm_iommu_create_mapping() and arm_iommu_attach_device(). > > > > > > Thank you. Yes, we need to call these functions otherwise iommu will not be enabled at all. > > > So my question is: > > > 1. in arm_iommu_create_mapping, we need to specify the base address > > > of the iova. Is these an API which can get this base address? I > > > mean, SMMU serves a lot of clients and maybe every client will > > > specify a range of iova which it needs. So as the center point of > > > these clients, does SMMU module has a function which can be used by > > > client to get this base address? > > > > The SMMU patch was sent but it depends on the following framework. > > > > [PATCH 0/5] IOMMU: Make IOMMU-API ready for GART-like hardware > > https://lkml.org/lkml/2012/1/19/170 > > > > Got it. Seems this patch hasn't been integrated yet. Besides, SMMU > module should do some implementations for this set/get attribute > functions as well, right? Yes, that's below: http://lists.linuxfoundation.org/pipermail/iommu/2012-January/003531.html > > > 2. I took a quick glance of tegra-smmu.c, I noticed that there is a > > > dts property named dma-window, which it's value is: <0x0 > > > 0x40000000>. Does this means the iova which SMMU handles is from 0 - > > > 1G? IIRC, SMMU handles 4G address space... > > > > It tries to avoid overwrapping 1-1 iovirt-phys mapping, which is > > necessary for some drivers right now. > > > > Sorry I didn't get it. What is overwrapping 1-1 iovirt-phys mapping? To create the mapping, Physical Address 0x12345678 == IO virtual Address 0x12345678 Then, even if device drivers are not aware of IOMMU, it should work. > > > 3. Right now in my drm driver, arm_iommu_attach_device failed with > > > an error code: -22(Invalid Argument). I think this is caused by > > > these codes in function smmu_iommu_attach_dev: > > > > > > map = (unsigned long)dev->platform_data; > > > if (!map) > > > return -EINVAL; > > > > > > So, does this mean the drm_device should have a "platform_data"(right now it is NULL so -EINVAL returned)? > > > I skimmed the codes of tegra-smmu.c, seems this "platform_data" has specific usage and should be composed in some rules. > > > Could you explain a little bit about this? > > > > You can skip that check with the following patch. > > > Yes, it works. Right now the framebuffer works on my T30. Great! -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
