Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 30 Sep 2020 18:06:26 +0200
From:   Thierry Reding <thierry.reding@gmail.com>
To:     Dmitry Osipenko <digetx@gmail.com>
Cc:     Nicolin Chen <nicoleotsuka@gmail.com>, joro@8bytes.org,
        krzk@kernel.org, vdumpa@nvidia.com, jonathanh@nvidia.com,
        linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and
 .attach_dev
Message-ID: <20200930160626.GD3833404@ulmo>
References: <20200930084258.25493-1-nicoleotsuka@gmail.com>
 <20200930084258.25493-3-nicoleotsuka@gmail.com>
 <20200930153131.GB3833404@ulmo>
 <ece615ad-8d6b-96ae-d8b4-9667aef17281@gmail.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256;
        protocol="application/pgp-signature"; boundary="sgneBHv3152wZ8jf"
Content-Disposition: inline
In-Reply-To: <ece615ad-8d6b-96ae-d8b4-9667aef17281@gmail.com>
User-Agent: Mutt/1.14.7 (2020-08-29)
Precedence: bulk


--sgneBHv3152wZ8jf
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Wed, Sep 30, 2020 at 06:36:52PM +0300, Dmitry Osipenko wrote:
>  I'...
> >> +	struct tegra_mc *mc =3D devm_tegra_get_memory_controller(dev);
> >> +	struct iommu_fwspec *fwspec =3D dev_iommu_fwspec_get(dev);
> >=20
> > It looks to me like the only reason why you need this new global API is
> > because PCI devices may not have a device tree node with a phandle to
> > the IOMMU. However, SMMU support for PCI will only be enabled if the
> > root complex has an iommus property, right? In that case, can't we
> > simply do something like this:
> >=20
> > 	if (dev_is_pci(dev))
> > 		np =3D find_host_bridge(dev)->of_node;
> > 	else
> > 		np =3D dev->of_node;
> >=20
> > ? I'm not sure exactly what find_host_bridge() is called, but I'm pretty
> > sure that exists.
> >=20
> > Once we have that we can still iterate over the iommus property and do
> > not need to rely on this global variable.
>=20
> This sounds more complicated than the current variant.
>=20
> Secondly, I'm already about to use the new tegra_get_memory_controller()
> API for all the T20/30/124/210 EMC and devfreq drivers.

Why do we need it there? They seem to work fine without it right now. If
it is required for new functionality, we can always make the dependent
on a DT reference via phandle without breaking any existing code.

Thierry

--sgneBHv3152wZ8jf
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=SlyZ
-----END PGP SIGNATURE-----

--sgneBHv3152wZ8jf--