> -----Original Message----- > From: iommu-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx [mailto:iommu- > bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Thierry Reding > Sent: Friday, June 27, 2014 12:29 PM > To: Rob Herring; Pawel Moll; Mark Rutland; Ian Campbell; Kumar Gala; > Stephen Warren; Arnd Bergmann; Will Deacon; Joerg Roedel > Cc: Olav Haugan; devicetree@xxxxxxxxxxxxxxx; Grant Grundler; Rhyland > Klein; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > Marc Zyngier; Allen Martin; Paul Walmsley; linux-tegra@xxxxxxxxxxxxxxx; > Cho KyongHo; Dave Martin; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Subject: Re: [RFC 01/10] iommu: Add IOMMU device registry > > On Thu, Jun 26, 2014 at 10:49:41PM +0200, Thierry Reding wrote: > > From: Thierry Reding <treding@xxxxxxxxxx> > > > > Add an IOMMU device registry for drivers to register with and > > implement a method for users of the IOMMU API to attach to an IOMMU > > device. This allows to support deferred probing and gives the IOMMU > > API a convenient hook to perform early initialization of a device if > necessary. > > > > Signed-off-by: Thierry Reding <treding@xxxxxxxxxx> > > --- > > drivers/iommu/iommu.c | 93 > > +++++++++++++++++++++++++++++++++++++++++++++++++++ > > include/linux/iommu.h | 27 +++++++++++++++ > > 2 files changed, 120 insertions(+) > > I thought that perhaps I should elaborate on this a bit since I have a > few ideas on how the API could be enhanced. > > > +static int of_iommu_attach(struct device *dev) { > > + struct of_phandle_iter iter; > > + struct iommu *iommu; > > + > > + mutex_lock(&iommus_lock); > > + > > + of_property_for_each_phandle_with_args(iter, dev->of_node, > "iommus", > > + "#iommu-cells", 0) { > > + bool found = false; > > + int err; > > + > > + /* skip disabled IOMMUs */ > > + if (!of_device_is_available(iter.out_args.np)) > > + continue; > > + > > + list_for_each_entry(iommu, &iommus, list) { > > + if (iommu->dev->of_node == iter.out_args.np) { > > + err = iommu->ops->attach(iommu, dev); > > + if (err < 0) { > > + } > > + > > + found = true; > > + } > > + } > > + > > + if (!found) { > > + mutex_unlock(&iommus_lock); > > + return -EPROBE_DEFER; > > + } > > + } > > + > > + mutex_unlock(&iommus_lock); > > + > > + return 0; > > +} > > + > > +static int of_iommu_detach(struct device *dev) { > > + /* TODO: implement */ > > + return -ENOSYS; > > +} > > + > > +int iommu_attach(struct device *dev) > > +{ > > + int err = 0; > > + > > + if (IS_ENABLED(CONFIG_OF) && dev->of_node) { > > + err = of_iommu_attach(dev); > > + if (!err) > > + return 0; > > + } > > + > > + return err; > > +} > > +EXPORT_SYMBOL_GPL(iommu_attach); > > I think it might make sense to introduce an explicit object for an IOMMU > master attachment. Maybe something like: > > struct iommu_master { > struct iommu *iommu; > struct device *dev; > > ... > }; > > iommu_attach() could then return a pointer to that attachment and the > IOMMU user driver could subsequently use that as a handle to access other > parts of the API. > > The reason is that if we ever need to support more than a single master > interface (and perhaps even multiple master interfaces on different > IOMMUs) for a single device, then we need a way for the IOMMU user to > differentiate between its master interfaces. > > > diff --git a/include/linux/iommu.h b/include/linux/iommu.h index > > 284a4683fdc1..ac2ceef194d4 100644 > > --- a/include/linux/iommu.h > > +++ b/include/linux/iommu.h > > @@ -43,6 +43,17 @@ struct notifier_block; typedef int > > (*iommu_fault_handler_t)(struct iommu_domain *, > > struct device *, unsigned long, int, void *); > > > > +struct iommu { > > + struct device *dev; > > + > > + struct list_head list; > > + > > + const struct iommu_ops *ops; > > +}; > > For reasons explained above, I also think that it would be a good idea to > modify the iommu_ops functions to take a struct iommu * as their first > argument. This may become important when one driver needs to support > multiple IOMMU devices. With the current API drivers have to rely on > global variables to track the driver-specific context. As far as I can > tell, only .domain_init(), .add_device(), .remove_device() and > .device_group(). .domain_init() could set up a pointer to struct iommu in > struct iommu_domain so the functions dealing with domains could gain > access to the IOMMU device via that pointer. Would the proposed interface be an alternate to the add_device interface? Also, how would the iommu group creation work? We are dependent on device driver initialization to attach device an IOMMU, but the add_device allows creation of iommu_groups during bus probing. Can't the same thing be achieved using the add device interface where an IOMMU driver can determine (in add_device) if the device is attached to a particular IOMMU. If the device is attached to that IOMMU then it can create the corresponding IOMMU group. IOMMU information can be stored in archdata. -Varun -- 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
