linux-kernel - Re: [PATCH v6 02/12] iommu: Add pasid_bits field in struct dev

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Message-ID: <20220511115952.GX49344@nvidia.com>
Date:   Wed, 11 May 2022 08:59:52 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Jean-Philippe Brucker <jean-philippe@...aro.org>
Cc:     Baolu Lu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 02/12] iommu: Add pasid_bits field in struct dev_iommu

On Wed, May 11, 2022 at 09:00:50AM +0100, Jean-Philippe Brucker wrote:

> > /**
> >  * struct iommu_device - IOMMU core representation of one IOMMU hardware
> >  *                       instance
> >  * @list: Used by the iommu-core to keep a list of registered iommus
> >  * @ops: iommu-ops for talking to this iommu
> >  * @dev: struct device for sysfs handling
> >  */
> > struct iommu_device {
> >         struct list_head list;
> >         const struct iommu_ops *ops;
> >         struct fwnode_handle *fwnode;
> >         struct device *dev;
> > };
> > 
> > I haven't checked ARM code yet, but it works for x86 as far as I can
> > see.
> 
> Arm also supports non-PCI PASID by reading a firmware property:
> 
>         device_property_read_u32(dev, "pasid-num-bits", &master->ssid_bits);
> 
> should be the only difference

That is not "ARM" that is generic DT/ACPI for platform devices and
should be handled by the core code in the same place it does PCI
discovery.

Jason