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

From: Mikko Perttunen <cyndis@kapsi.fi>
To: Robin Murphy <robin.murphy@arm.com>, Will Deacon <will@kernel.org>
Cc: devicetree@vger.kernel.org, krzysztof.kozlowski@canonical.com,
	linux-kernel@vger.kernel.org, robh+dt@kernel.org,
	jonathanh@nvidia.com, iommu@lists.linux-foundation.org,
	thierry.reding@gmail.com, dri-devel@lists.freedesktop.org,
	linux-tegra@vger.kernel.org,
	Mikko Perttunen <mperttunen@nvidia.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v5 5/9] iommu/arm-smmu: Attach to host1x context device bus
Date: Mon, 16 May 2022 14:20:18 +0300	[thread overview]
Message-ID: <020a8244-760e-fe7c-594a-1d85e5645dbe@kapsi.fi> (raw)
In-Reply-To: <099cf0f9-5c27-0247-7c5e-6704a9527b11@arm.com>

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@kapsi.fi wrote:
>>>> From: Mikko Perttunen <mperttunen@nvidia.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@nvidia.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?

Thanks,
Mikko
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