From mboxrd@z Thu Jan  1 00:00:00 1970
From: robin.murphy@arm.com (Robin Murphy)
Date: Tue, 9 Jan 2018 11:58:14 +0000
Subject: [PATCH] iommu/exynos: Don't unconditionally steal bus ops
In-Reply-To: <878c7791-ef37-adc7-8186-27455f2ef67f@samsung.com>
References: <CGME20180108192758epcas4p196b256cafeb8fce0359223c7f2aa960c@epcas4p1.samsung.com>
 <1432caf4ecfb077bb54f0115cb5e12b6620e8bfa.1515439558.git.robin.murphy@arm.com>
 <878c7791-ef37-adc7-8186-27455f2ef67f@samsung.com>
Message-ID: <584abc4c-7582-f519-554a-d7ac4e49bf8b@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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@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