From mboxrd@z Thu Jan 1 00:00:00 1970 From: tfiga@chromium.org (Tomasz Figa) Date: Tue, 10 Mar 2015 02:00:44 +0900 Subject: [PATCH 2/5] iommu/mediatek: Add mt8173 IOMMU driver In-Reply-To: <1425912389.4871.19.camel@mtksdaap41> References: <1425638900-24989-1-git-send-email-yong.wu@mediatek.com> <1425638900-24989-3-git-send-email-yong.wu@mediatek.com> <1425912389.4871.19.camel@mtksdaap41> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Mar 9, 2015 at 11:46 PM, Yingjoe Chen wrote: > On Mon, 2015-03-09 at 20:11 +0900, Tomasz Figa wrote: > <...> >> > +/* >> > + * pimudev is a global var for dma_alloc_coherent. >> > + * It is not accepatable, we will delete it if "domain_alloc" is enabled >> > + */ >> > +static struct device *pimudev; >> >> This is indeed not acceptable. Could you replace dma_alloc_coherent() >> with something that doesn't require device pointer, e.g. >> alloc_pages()? (Although that would require you to handle cache >> maintenance in the driver, due to cached memory allocated.) I need to >> think about a better solution for this. > > Hi, > > For 2nd level page table, we use cached memory now. Currently we are > using __dma_flush_range to flush the cache, which is also unacceptable. > > For proper cache management, we'll need to use dma_map_single or > dma_sync_*, which still need a deivce*. Looking at how already mainlined drivers do this, they either use dmac_flush_range() (https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/iommu/msm_iommu.c?id=refs/tags/v4.0-rc3#n80) or directly __cpuc_flush_dcache_area() and outer_flush_range() (https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/iommu/rockchip-iommu.c?id=refs/tags/v4.0-rc3#n93). Joerg, what's your opinion on this? Best regards, Tomasz