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

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Message-ID: <099cf0f9-5c27-0247-7c5e-6704a9527b11@arm.com>
Date:   Mon, 16 May 2022 11:44:41 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Mikko Perttunen <cyndis@...si.fi>, Will Deacon <will@...nel.org>
Cc:     thierry.reding@...il.com, 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 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.