linux-kernel - Re: [PATCH v5 5/9] iommu/arm-smmu: Attach to host1x context device bus

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Message-ID: <YoJakX0ms7rBF3ia@orome>
Date:   Mon, 16 May 2022 16:07:13 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Mikko Perttunen <cyndis@...si.fi>
Cc:     Robin Murphy <robin.murphy@....com>, Will Deacon <will@...nel.org>,
        jonathanh@...dia.com, joro@...tes.org, robh+dt@...nel.org,
        krzysztof.kozlowski@...onical.com, linux-tegra@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Mikko Perttunen <mperttunen@...dia.com>
Subject: Re: [PATCH v5 5/9] iommu/arm-smmu: Attach to host1x context device
 bus

On Mon, May 16, 2022 at 02:20:18PM +0300, Mikko Perttunen wrote:
> On 5/16/22 13:44, Robin Murphy wrote:
> > On 2022-05-16 11:13, Mikko Perttunen wrote:
> > > On 5/16/22 13:07, Will Deacon wrote:
> > > > On Mon, May 16, 2022 at 11:52:54AM +0300, cyndis@...si.fi wrote:
> > > > > From: Mikko Perttunen <mperttunen@...dia.com>
> > > > > 
> > > > > Set itself as the IOMMU for the host1x context device bus, containing
> > > > > "dummy" devices used for Host1x context isolation.
> > > > > 
> > > > > Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
> > > > > ---
> > > > >   drivers/iommu/arm/arm-smmu/arm-smmu.c | 13 +++++++++++++
> > > > >   1 file changed, 13 insertions(+)
> > > > > 
> > > > > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > > > > b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > > > > index 568cce590ccc..9ff54eaecf81 100644
> > > > > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > > > > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > > > > @@ -39,6 +39,7 @@
> > > > >   #include <linux/amba/bus.h>
> > > > >   #include <linux/fsl/mc.h>
> > > > > +#include <linux/host1x_context_bus.h>
> > > > >   #include "arm-smmu.h"
> > > > > @@ -2053,8 +2054,20 @@ static int arm_smmu_bus_init(struct
> > > > > iommu_ops *ops)
> > > > >               goto err_reset_pci_ops;
> > > > >       }
> > > > >   #endif
> > > > > +#ifdef CONFIG_TEGRA_HOST1X_CONTEXT_BUS
> > > > > +    if (!iommu_present(&host1x_context_device_bus_type)) {
> > > > > +        err = bus_set_iommu(&host1x_context_device_bus_type, ops);
> > > > > +        if (err)
> > > > > +            goto err_reset_fsl_mc_ops;
> > > > > +    }
> > > > > +#endif
> > > > > +
> > > > >       return 0;
> > > > > +err_reset_fsl_mc_ops: __maybe_unused;
> > > > > +#ifdef CONFIG_FSL_MC_BUS
> > > > > +    bus_set_iommu(&fsl_mc_bus_type, NULL);
> > > > > +#endif
> > > > 
> > > > bus_set_iommu() is going away:
> > > > 
> > > > https://lore.kernel.org/r/cover.1650890638.git.robin.murphy@arm.com
> > > > 
> > > > Will
> > > 
> > > Thanks for the heads-up. Robin had pointed out that this work was
> > > ongoing but I hadn't seen the patches yet. I'll look into it.
> > 
> > Although that *is* currently blocked on the mystery intel-iommu problem
> > that I can't reproduce... If this series is ready to land right now for
> > 5.19 then in principle that might be the easiest option overall.
> > Hopefully at least patch #2 could sneak in so that the compile-time
> > dependencies are ready for me to roll up host1x into the next rebase of
> > "iommu: Always register bus notifiers".
> > 
> > Cheers,
> > Robin.
> 
> My guess is that the series as a whole is not ready to land in the 5.19
> timeframe, but #2 could be possible.
> 
> Thierry, any opinion?

Dave and Daniel typically want new material to be in by -rc6 and I've
already sent the PR for this cycle. I can ask them if they'd take
another one, though, if it make things simpler for the next cycle.

Thierry

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