Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH 7/7] iommu/arm-smmu: Allow building as a module
To:     Rob Herring <robh@kernel.org>, Will Deacon <will@kernel.org>
Cc:     iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        Joerg Roedel <joro@8bytes.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
References: <20191030145112.19738-1-will@kernel.org>
 <20191030145112.19738-8-will@kernel.org>
 <20191030152212.ifzhl2w3knapc367@bogus>
From:   Robin Murphy <robin.murphy@arm.com>
Message-ID: <9ffbf469-83a7-4ebb-504c-ac17c2f526cc@arm.com>
Date:   Wed, 30 Oct 2019 15:33:26 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.6.1
MIME-Version: 1.0
In-Reply-To: <20191030152212.ifzhl2w3knapc367@bogus>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-GB
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 30/10/2019 15:22, Rob Herring wrote:
> On Wed, Oct 30, 2019 at 02:51:12PM +0000, Will Deacon wrote:
>> By conditionally dropping support for the legacy binding and exporting
>> the newly introduced 'arm_smmu_impl_init()' function we can allow the
>> ARM SMMU driver to be built as a module.
>>
>> Signed-off-by: Will Deacon <will@kernel.org>
>> ---
>>   drivers/iommu/Kconfig         | 14 ++++++++-
>>   drivers/iommu/arm-smmu-impl.c |  6 ++++
>>   drivers/iommu/arm-smmu.c      | 54 +++++++++++++++++++++--------------
>>   3 files changed, 51 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
>> index 7583d47fc4d5..02703f51e533 100644
>> --- a/drivers/iommu/Kconfig
>> +++ b/drivers/iommu/Kconfig
>> @@ -350,7 +350,7 @@ config SPAPR_TCE_IOMMU
>>   
>>   # ARM IOMMU support
>>   config ARM_SMMU
>> -	bool "ARM Ltd. System MMU (SMMU) Support"
>> +	tristate "ARM Ltd. System MMU (SMMU) Support"
>>   	depends on (ARM64 || ARM) && MMU
>>   	select IOMMU_API
>>   	select IOMMU_IO_PGTABLE_LPAE
>> @@ -362,6 +362,18 @@ config ARM_SMMU
>>   	  Say Y here if your SoC includes an IOMMU device implementing
>>   	  the ARM SMMU architecture.
>>   
>> +config ARM_SMMU_LEGACY_DT_BINDINGS
>> +	bool "Support the legacy \"mmu-masters\" devicetree bindings"
> 
> Can't we just remove this now? The only user is Seattle. Is anyone still
> using Seattle AND DT? There's been no real dts change since Feb '16.
> There's a bit of clean-up needed in the Seattle dts files, so I'd like
> to remove them if there's not users.
> 
> If there are users, can't we just make them move to the new binding?
> Yes compatibility, but that really depends on the users caring.

Apparently it's also in the wild on Cavium ThunderX/OcteonTX machines as 
well :(

> I though Calxeda was using this too, but I guess we didn't get that
> finished. We should probably remove that secure mode flag as well.

FWIW the secure quirk still comes in useful every now and then when 
people prototype stuff on 32-bit VExpress, where it turns out an SMMU is 
about the only thing which cares whether you're running Linux in Secure 
mode or not.

Robin.