[PATCH] iommu/exynos: Don't unconditionally steal bus ops

[Robin Murphy]

On 09/01/18 09:59, Marek Szyprowski wrote:
> Hi Robin,
> 
> On 2018-01-08 20:27, Robin Murphy wrote:
>> Removing the early device registration hook overlooked the fact that
>> it only ran conditionally on a compatible device being present in the
>> DT. With exynos_iommu_init() now running as an unconditional initcall,
>> problems arise on non-Exynos systems when other IOMMU drivers find
>> themselves unable to install their ops on the platform bus, or at worst
>> the Exynos ops get called with someone else's domain and all hell breaks
>> loose.
>>
>> Fix this by delaying the setting of bus ops until an Exynos IOMMU is
>> actually found, to replicate the previous order of events.
>>
>> Fixes: 928055a01b3f ("iommu/exynos: Remove custom platform device 
>> registration code")
>> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> 
> Right, my fault. However I will prefer to resurrect code added initially
> by commit a7b67cd5d9af "iommu/exynos: Play nice in multi-platform builds".
> There is no need to do all the things done in the exynos_iommu_init on
> non-Exynos platforms.

Yeah; I had a moment of doubt and left the rest as-is, but I guess all 
of that global setup could in fact be delayed until the first probe, as 
with dma_dev. Anyway, I'll respin just the minimal fix to un-break 
multiplatform, and leave any further refactoring up to you.

Thanks,
Robin.

>> ---
>>   drivers/iommu/exynos-iommu.c | 16 +++++++---------
>>   1 file changed, 7 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
>> index 6a96a4c42153..e9e756156429 100644
>> --- a/drivers/iommu/exynos-iommu.c
>> +++ b/drivers/iommu/exynos-iommu.c
>> @@ -574,6 +574,12 @@ static int __init exynos_sysmmu_probe(struct 
>> platform_device *pdev)
>>       struct sysmmu_drvdata *data;
>>       struct resource *res;
>> +    if (platform_bus_type->iommu_ops != &exynos_iommu_ops) {
>> +        ret = bus_set_iommu(&platform_bus_type, &exynos_iommu_ops);
>> +        if (ret)
>> +            return ret;
>> +    }
>> +
>>       data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>>       if (!data)
>>           return -ENOMEM;
>> @@ -1367,16 +1373,8 @@ static int __init exynos_iommu_init(void)
>>           goto err_zero_lv2;
>>       }
>> -    ret = bus_set_iommu(&platform_bus_type, &exynos_iommu_ops);
>> -    if (ret) {
>> -        pr_err("%s: Failed to register exynos-iommu driver.\n",
>> -                                __func__);
>> -        goto err_set_iommu;
>> -    }
>> -
>>       return 0;
>> -err_set_iommu:
>> -    kmem_cache_free(lv2table_kmem_cache, zero_lv2_table);
>> +
>>   err_zero_lv2:
>>       platform_driver_unregister(&exynos_sysmmu_driver);
>>   err_reg_driver:
> 
> Best regards