From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751486Ab2AYGwC (ORCPT ); Wed, 25 Jan 2012 01:52:02 -0500 Received: from mail-lpp01m010-f46.google.com ([209.85.215.46]:57283 "EHLO mail-lpp01m010-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751040Ab2AYGwA convert rfc822-to-8bit (ORCPT ); Wed, 25 Jan 2012 01:52:00 -0500 MIME-Version: 1.0 In-Reply-To: <20120123142706.GA6269@8bytes.org> References: <001001ccc625$0afa7ee0$20ef7ca0$%cho@samsung.com> <20120123142706.GA6269@8bytes.org> Date: Wed, 25 Jan 2012 15:51:58 +0900 X-Google-Sender-Auth: nKv2LDz7WtkuWXo18LdBoqpzKw8 Message-ID: Subject: Re: [PATCH v8 2/2] iommu/exynos: Add iommu driver for Exynos Platforms From: KyongHo Cho To: Joerg Roedel Cc: Kukjin Kim , Subash Patel , linux-kernel@vger.kernel.org, Younglak Kim , iommu@lists.linux-foundation.org, linux-samsung-soc@vger.kernel.org, Kyungmin Park , Sanghyun Lee , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Mon, Jan 23, 2012 at 11:27 PM, Joerg Roedel wrote: > Hi, > > please also get and inclue Acks from the Exynos maintainer for the next > post. > Since I have a compiling config for exynos now I will merge the patches > when you have the Acks and addressed or explained the issues I pointed > out below. > Thanks for review! I will include the Acks in the next patchset. I will post the next patchset with corrections by the day after tomorrow. And sorry for late reply. I had holidays for the new year's day based on Lunar system. > On Thu, Dec 29, 2011 at 09:26:08PM +0900, KyongHo Cho wrote: >> +static void exynos_iommu_domain_destroy(struct iommu_domain *domain) >> +{ >> +     struct exynos_iommu_domain *priv = domain->priv; >> +     struct list_head *pos, *n; >> +     unsigned long flags; >> +     int i; >> + >> +     WARN_ON(!list_empty(&priv->clients)); > > This isn't really a problem. We allow destroying a domain with devices > attached. So this WARN_ON is not necessary. > OK. BTW, Isn't it a problem when a device driver does not know that its iommu domain is destroyed? Can we regards that it is the faulty use of iommu API? >> +static int exynos_iommu_map(struct iommu_domain *domain, unsigned long iova, >> +                      phys_addr_t paddr, size_t size, int prot) >> +{ >> +     struct exynos_iommu_domain *priv = domain->priv; >> +     unsigned long *entry; >> +     unsigned long flags; >> +     int ret = -ENOMEM; >> + >> +     BUG_ON(priv->pgtable == NULL); >> + >> +     spin_lock_irqsave(&priv->pgtablelock, flags); >> + >> +     entry = section_entry(priv->pgtable, iova); >> + >> +     if (size >= SECT_SIZE) { >> +             ret = lv1set_section(entry, paddr, size >> SECT_ORDER, >> +                                     &priv->lv2entcnt[lv1ent_offset(iova)]); > > This looks like you are partially re-implementing behavior of generic > code because you are mapping multiple sections at once. The generic map > code already splits up the address range correctly, so no need to do > this in the driver (unless there is some benefit in the hardware, like > an IOTLB entry that can cover multiple sections or something similar). > Yes, I wanted to avoid repeated function call by iommu_map(). s5p_iommu_map() maps once for the same page size since it is efficient and simple. That's why this driver initializes domain->pgsize_bitmap with 0xFFFFF000 even though our IOMMU driver just supports 3 different page sizes including 4KB, 64KB and 1MB. Do you think it is better for s5p_iommu_map() to map just one page at once? >> +static size_t exynos_iommu_unmap(struct iommu_domain *domain, >> +                                            unsigned long iova, size_t size) >> +{ >> +     struct exynos_iommu_domain *priv = domain->priv; >> +     struct iommu_client *client; >> +     unsigned long flags; >> + >> +     BUG_ON(priv->pgtable == NULL); >> + >> +     spin_lock_irqsave(&priv->pgtablelock, flags); >> + >> +     while (size != 0) { >> +             int i, nent, order; >> +             unsigned long *pent, *sent; > > Same with this while-loop. This looks like it re-implements behavior > from the generic code. > If a region to unmap consists of tens of pages there is no way to avoid flushing IOTLB repeatedly. Out iommu driver doesn't need to flush IOTLB more than once for a region to unmap. Do you think the driver is better to unmaps just one page at once though flushing IOTLB repeatedly? Thank you. KyongHo