linux-kernel - Re: [Freedreno] [PATCH v9 4/7] iommu/arm-smmu: Add a pointer to the attached device to smmu_domain

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Message-ID: <20200713171917.GA3815@jcrouse1-lnx.qualcomm.com>
Date:   Mon, 13 Jul 2020 11:19:17 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Will Deacon <will@...nel.org>
Cc:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        John Stultz <john.stultz@...aro.org>,
        freedreno@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [Freedreno] [PATCH v9 4/7] iommu/arm-smmu: Add a pointer to the
 attached device to smmu_domain

On Mon, Jul 13, 2020 at 04:09:02PM +0100, Will Deacon wrote:
> On Fri, Jun 26, 2020 at 02:00:38PM -0600, Jordan Crouse wrote:
> > Add a link to the pointer to the struct device that is attached to a
> > domain. This makes it easy to get the pointer if it is needed in the
> > implementation specific code.
> > 
> > Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
> > ---
> > 
> >  drivers/iommu/arm-smmu.c | 6 ++++--
> >  drivers/iommu/arm-smmu.h | 1 +
> >  2 files changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> > index 048de2681670..060139452c54 100644
> > --- a/drivers/iommu/arm-smmu.c
> > +++ b/drivers/iommu/arm-smmu.c
> > @@ -668,7 +668,8 @@ static void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx)
> >  }
> >  
> >  static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> > -					struct arm_smmu_device *smmu)
> > +					struct arm_smmu_device *smmu,
> > +					struct device *dev)
> >  {
> >  	int irq, start, ret = 0;
> >  	unsigned long ias, oas;
> > @@ -801,6 +802,7 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> >  		cfg->asid = cfg->cbndx;
> >  
> >  	smmu_domain->smmu = smmu;
> > +	smmu_domain->dev = dev;
> >  
> >  	pgtbl_cfg = (struct io_pgtable_cfg) {
> >  		.pgsize_bitmap	= smmu->pgsize_bitmap,
> > @@ -1190,7 +1192,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
> >  		return ret;
> >  
> >  	/* Ensure that the domain is finalised */
> > -	ret = arm_smmu_init_domain_context(domain, smmu);
> > +	ret = arm_smmu_init_domain_context(domain, smmu, dev);
> >  	if (ret < 0)
> >  		goto rpm_put;
> >  
> > diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
> > index 5f2de20e883b..d33cfe26b2f5 100644
> > --- a/drivers/iommu/arm-smmu.h
> > +++ b/drivers/iommu/arm-smmu.h
> > @@ -345,6 +345,7 @@ struct arm_smmu_domain {
> >  	struct mutex			init_mutex; /* Protects smmu pointer */
> >  	spinlock_t			cb_lock; /* Serialises ATS1* ops and TLB syncs */
> >  	struct iommu_domain		domain;
> > +	struct device			*dev;	/* Device attached to this domain */
> 
> This really doesn't feel right to me -- you can generally have multiple
> devices attached to a domain and they can come and go without the domain
> being destroyed. Perhaps you could instead identify the GPU during
> cfg_probe() and squirrel that information away somewhere?

I need some help here. The SMMU device (qcom,adreno-smmu) will have at least two
stream ids from two different platform devices (GPU and GMU) and I need to
configure split-pagetable and stall/terminate differently on the two domains.

I couldn't figure out a way to identify the platform device before it attached
itself with iommu_attach_device. I tried poking around in fwspec but got lost.

If there is a way we can uniquely identify the devices (by stream id maybe) then
we could use that though I have reservations about hard coding stream IDs in the
impl driver. That said, the stream IDs have never changed in the life of the
GPU so maybe it's not a problem that needs solving.

Jordan

> The rest of the series looks ok to me.
> 
> Will
> _______________________________________________
> Freedreno mailing list
> Freedreno@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/freedreno

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