Re: [PATCH v7 03/25] iommu: Init iommu-groups support earlier, in core_initcall

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hello,

On 2015-05-23 18:23, Laurent Pinchart wrote:
> Hi Marek,
>
> Thank you for the patch.
>
> On Tuesday 19 May 2015 15:20:23 Marek Szyprowski wrote:
>> iommu_group_alloc might be called very early in case of iommu controllers
>> activated from of_iommu, so ensure that this part of subsystem is ready
>> when devices are being populated from device-tree (core_initcall seems to
>> be okay for this case).
>>
>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> ---
>>   drivers/iommu/iommu.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index d4f527e56679..37a6aa8f318b 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -1207,7 +1207,7 @@ static int __init iommu_init(void)
>>
>>   	return 0;
>>   }
>> -arch_initcall(iommu_init);
>> +core_initcall(iommu_init);
> I'll let Joerg comment on this, but this initcall ordering dance always makes
> me feel that something isn't quite right. Have you had a chance to look at the
> patch series I posted about a week ago to implement IOMMU probe deferral
> support ?

I will try to check your IOMMU probe deferal, but for the time being 
changing the
initcall priority was the simplest way to get everything working with 
iommu_groups
(what was a requirement from Joerg).

I also don't like the initcall ordering hacks, but this change seems to 
be the
right approach. Probe deferal is convenient for development purpose and 
all king of
hotpluggable solutions, but imho for typical cases system should be 
tuned to avoid
deferal to reduce overhead on boot.

If possible I would like to avoid having dependency on your 
deferal-probe patches
and get the basic Exynos IOMMU support finally merged. There are still other
enhancements to Exynos IOMMU driver that depend on it and need real 
discussion
(like real runtime pm and exposing particular iommu controllers via dma 
api).

>
>>   int iommu_domain_get_attr(struct iommu_domain *domain,
>>   			  enum iommu_attr attr, void *data)
>

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland