linux-kernel - Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and .attach

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Message-ID: <20200930101909.GA1147@pi3>
Date:   Wed, 30 Sep 2020 12:19:09 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     thierry.reding@...il.com, joro@...tes.org, digetx@...il.com,
        vdumpa@...dia.com, jonathanh@...dia.com,
        linux-tegra@...r.kernel.org, iommu@...ts.linux-foundation.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] iommu/tegra-smmu: Rework .probe_device and
 .attach_dev

On Wed, Sep 30, 2020 at 02:40:32AM -0700, Nicolin Chen wrote:
> On Wed, Sep 30, 2020 at 11:21:14AM +0200, Krzysztof Kozlowski wrote:
> > On Wed, 30 Sep 2020 at 10:48, Nicolin Chen <nicoleotsuka@...il.com> wrote:
> > >
> > > Previously the driver relies on bus_set_iommu() in .probe() to call
> > > in .probe_device() function so each client can poll iommus property
> > > in DTB to configure fwspec via tegra_smmu_configure(). According to
> > > the comments in .probe(), this is a bit of a hack. And this doesn't
> > > work for a client that doesn't exist in DTB, PCI device for example.
> > >
> > > Actually when a device/client gets probed, the of_iommu_configure()
> > > will call in .probe_device() function again, with a prepared fwspec
> > > from of_iommu_configure() that reads the SWGROUP id in DTB as we do
> > > in tegra-smmu driver.
> > >
> > > Additionally, as a new helper devm_tegra_get_memory_controller() is
> > > introduced, there's no need to poll the iommus property in order to
> > > get mc->smmu pointers or SWGROUP id.
> > >
> > > This patch reworks .probe_device() and .attach_dev() by doing:
> > > 1) Using fwspec to get swgroup id in .attach_dev/.dettach_dev()
> > > 2) Removing DT polling code, tegra_smmu_find/tegra_smmu_configure()
> > > 3) Calling devm_tegra_get_memory_controller() in .probe_device()
> > > 4) Also dropping the hack in .probe() that's no longer needed.
> > >
> > > Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> > > ---
> > >
> > > Changelog
> > > v2->v3
> > >  * Used devm_tegra_get_memory_controller() to get mc pointer
> > >  * Replaced IS_ERR_OR_NULL with IS_ERR in .probe_device()
> > > v1->v2
> > >  * Replaced in .probe_device() tegra_smmu_find/tegra_smmu_configure()
> > >    with tegra_get_memory_controller call.
> > >  * Dropped the hack in tegra_smmu_probe().
> > >
> > >  drivers/iommu/tegra-smmu.c | 144 ++++++++++---------------------------
> > >  1 file changed, 36 insertions(+), 108 deletions(-)
> > >
> > > diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
> > > index 6a3ecc334481..636dc3b89545 100644
> > > --- a/drivers/iommu/tegra-smmu.c
> > > +++ b/drivers/iommu/tegra-smmu.c
> > > @@ -61,6 +61,8 @@ struct tegra_smmu_as {
> > >         u32 attr;
> > >  };
> > >
> > > +static const struct iommu_ops tegra_smmu_ops;
> > 
> > I cannot find in this patch where this is assigned.
> 
> Because it's already set in probe():
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/iommu/tegra-smmu.c#n1162
> 
> And my PATCH-3 sets it for PCI bus also.

OK, good point. Thanks for explanation.

Best regards,
Krzysztof