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From: Will Deacon <will@kernel.org>
To: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
	linux-arm-msm@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
	Robin Murphy <robin.murphy@arm.com>,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
	John Stultz <john.stultz@linaro.org>,
	freedreno@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [Freedreno] [PATCH v9 4/7] iommu/arm-smmu: Add a pointer to the attached device to smmu_domain
Date: Thu, 16 Jul 2020 09:50:53 +0100	[thread overview]
Message-ID: <20200716085053.GB6771@willie-the-truck> (raw)
In-Reply-To: <20200713171917.GA3815@jcrouse1-lnx.qualcomm.com>

On Mon, Jul 13, 2020 at 11:19:17AM -0600, Jordan Crouse wrote:
> 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:
> > > 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.

Hmm. How does the GPU driver know which context bank is assigned to the GPU
and which one is assigned to the GMU? I assume it needs this information so
that it can play its nasty tricks with the TTBR registers?

I ask because if we need to guarantee stability of the context-bank
assignment, then you could match on that in the ->init_context() callback,
but now I worry that it currently works by luck :/

Do we need to add an extra callback to allocate the context bank?

Will
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  reply	other threads:[~2020-07-16  8:51 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-26 20:00 [PATCH v9 0/7] iommu/arm-smmu: Enable split pagetable support Jordan Crouse
2020-06-26 20:00 ` [PATCH v9 1/7] iommu/arm-smmu: Pass io-pgtable config to implementation specific function Jordan Crouse
2020-06-26 20:00 ` [PATCH v9 2/7] iommu/arm-smmu: Add support for split pagetables Jordan Crouse
2020-07-02 20:22   ` Rob Clark
2020-06-26 20:00 ` [PATCH v9 3/7] dt-bindings: arm-smmu: Add compatible string for Adreno GPU SMMU Jordan Crouse
2020-06-26 20:00 ` [PATCH v9 4/7] iommu/arm-smmu: Add a pointer to the attached device to smmu_domain Jordan Crouse
2020-07-13 15:09   ` Will Deacon
2020-07-13 17:19     ` [Freedreno] " Jordan Crouse
2020-07-16  8:50       ` Will Deacon [this message]
2020-07-16 14:10         ` Rob Clark
2020-07-16 15:16         ` Jordan Crouse
2020-06-26 20:00 ` [PATCH v9 5/7] iommu/arm-smmu: Add implementation for the adreno GPU SMMU Jordan Crouse
2020-06-26 20:00 ` [PATCH v9 6/7] drm/msm: Set the global virtual address range from the IOMMU domain Jordan Crouse
2020-06-27 17:10   ` [Freedreno] " Rob Clark
2020-06-29 14:52     ` Jordan Crouse
2020-06-26 20:00 ` [PATCH v9 7/7] arm: dts: qcom: sm845: Set the compatible string for the GPU SMMU Jordan Crouse
2020-07-01 10:11 ` [PATCH v9 0/7] iommu/arm-smmu: Enable split pagetable support Sai Prakash Ranjan

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