linux-kernel - Re: [PATCH v7 3/3] iommu/tegra-smmu: Add PCI support

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Message-ID: <20201015041346.GA13936@Asurada-Nvidia>
Date:   Wed, 14 Oct 2020 21:13:47 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     thierry.reding@...il.com, joro@...tes.org, digetx@...il.com,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, jonathanh@...dia.com
Subject: Re: [PATCH v7 3/3] iommu/tegra-smmu: Add PCI support

On Wed, Oct 14, 2020 at 06:42:36PM +0100, Robin Murphy wrote:
> On 2020-10-09 17:19, Nicolin Chen wrote:
> > This patch simply adds support for PCI devices.
> > 
> > Reviewed-by: Dmitry Osipenko <digetx@...il.com>
> > Tested-by: Dmitry Osipenko <digetx@...il.com>
> > Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>
> > ---
> > 
> > Changelog
> > v6->v7
> >   * Renamed goto labels, suggested by Thierry.
> > v5->v6
> >   * Added Dmitry's Reviewed-by and Tested-by.
> > v4->v5
> >   * Added Dmitry's Reviewed-by
> > v3->v4
> >   * Dropped !iommu_present() check
> >   * Added CONFIG_PCI check in the exit path
> > v2->v3
> >   * Replaced ternary conditional operator with if-else in .device_group()
> >   * Dropped change in tegra_smmu_remove()
> > v1->v2
> >   * Added error-out labels in tegra_smmu_probe()
> >   * Dropped pci_request_acs() since IOMMU core would call it.
> > 
> >   drivers/iommu/tegra-smmu.c | 35 +++++++++++++++++++++++++----------
> >   1 file changed, 25 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
> > index be29f5977145..2941d6459076 100644
> > --- a/drivers/iommu/tegra-smmu.c
> > +++ b/drivers/iommu/tegra-smmu.c
> > @@ -10,6 +10,7 @@
> >   #include <linux/kernel.h>
> >   #include <linux/of.h>
> >   #include <linux/of_device.h>
> > +#include <linux/pci.h>
> >   #include <linux/platform_device.h>
> >   #include <linux/slab.h>
> >   #include <linux/spinlock.h>
> > @@ -865,7 +866,11 @@ static struct iommu_group *tegra_smmu_device_group(struct device *dev)
> >   	group->smmu = smmu;
> >   	group->soc = soc;
> > -	group->group = iommu_group_alloc();
> > +	if (dev_is_pci(dev))
> > +		group->group = pci_device_group(dev);
> 
> Just to check, is it OK to have two or more swgroups "owning" the same
> iommu_group if an existing one gets returned here? It looks like that might
> not play nice with the use of iommu_group_set_iommudata().

Do you mean by "gets returned here" the "IS_ERR" check below?

> Robin.
> 
> > +	else
> > +		group->group = generic_device_group(dev);
> > +
> >   	if (IS_ERR(group->group)) {
> >   		devm_kfree(smmu->dev, group);
> >   		mutex_unlock(&smmu->lock);