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charset="iso-2022-jp" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: TYWPR01MB9420.jpnprd01.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0cd66900-a36e-481f-bb66-08da52809b38 X-MS-Exchange-CrossTenant-originalarrivaltime: 20 Jun 2022 05:49:13.9668 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: f109924e-fb71-4ba0-b2cc-65dcdf6fbe4f X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: HRHuSwsiOsBmEL0idJc1Zf+EtXSeU1vPhirPAgZ3+1yNuxIJcdKt1bISnCDNxhseln4vNlSM34ErwxwC9WYNz4ZqL5GkVZUcTjWQlXmpLQWZ+NBptShIYlCjDzDoLAK9 X-MS-Exchange-Transport-CrossTenantHeadersStamped: TYAPR01MB2238 X-OriginatorOrg: toshiba.co.jp Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Thanks for your review. > -----Original Message----- > From: Jason Gunthorpe > Sent: Thursday, May 26, 2022 3:27 AM > To: Baolu Lu > Cc: iwamatsu nobuhiro(岩松 信洋 □ＳＷＣ◯ＡＣＴ) > ; Joerg Roedel ; Will > Deacon ; Rob Herring ; > devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; > iommu@lists.linux-foundation.org; ishikawa yuji(石川 悠司 ○ＲＤＣ□ＡＩＴ > Ｃ○ＥＡ開) ; > linux-arm-kernel@lists.infradead.org > Subject: Re: [PATCH 1/3] iommu: Add Visconti5 IOMMU driver > > On Wed, May 25, 2022 at 02:26:37PM +0800, Baolu Lu wrote: > > On 2022/5/25 09:31, Nobuhiro Iwamatsu wrote: > > > +static const struct iommu_ops visconti_atu_ops = { > > > + .domain_alloc = visconti_atu_domain_alloc, > > > + .probe_device = visconti_atu_probe_device, > > > + .release_device = visconti_atu_release_device, > > > + .device_group = generic_device_group, > > > + .of_xlate = visconti_atu_of_xlate, > > > + .pgsize_bitmap = ATU_IOMMU_PGSIZE_BITMAP, > > > + .default_domain_ops = &(const struct iommu_domain_ops) { > > > + .attach_dev = visconti_atu_attach_device, > > > + .detach_dev = visconti_atu_detach_device, > > > > The detach_dev callback is about to be deprecated. The new drivers > > should implement the default domain and blocking domain instead. > > Yes please, new drivers need to use default_domains. > > It is very strange that visconti_atu_detach_device() does nothing. It is not > required that a domain is fully unmapped before being destructed, I think > detach should set ATU_AT_EN to 0. I see, I rethink implementation. > > What behavior does the HW have when ATU_AT_ENTRY_EN == 0? If DMA is > rejected then this driver should have a IOMMU_DOMAIN_BLOCKING and > return that from ops->def_domain_type(). If ATU_AT_ENTRY_EN is 0, nothing happens. It does not work with IOMMU, it works with the memory space set in device tree. Also, I investigate about IOMMU_DOMAIN_BLOCKING. > > Attaching a the blocking domain should set ATU_AT_ENTRY_EN = 0 > > Also, if I surmise how this works properly, it is not following the iommu API to > halt all DMA during map/unmap operations. Should at least document this and > explain why it is OK.. I see, I will check DMA during map and unmap operations. > > I'm feeling like these "special" drivers need some kind of handshake with their > only users because they don't work with things like VFIO.. Since the devices that utilize this IOMMU function are fixed, I do not think that a special handshake is required. Could you you tell me where you thought you needed a handshake? Best regards, Nobuhiro > > Jason