Subject: [PATCH v3 2/9] iommu/of: Consolidate device creation workarounds

From: [email-masked] (Will Deacon)
Date: Fri, 1 Jul 2016 13:29:55 +0100

On Fri, Jul 01, 2016 at 12:19:51PM +0100, Robin Murphy wrote:
> On 01/07/16 11:32, Marek Szyprowski wrote:
> > Frankly, I would avoid moving this workaround to the iommu core. IMHO the
> > best solution would be to let IOMMU controllers to be instantiated as
> > normal
> > devices and implement proper support in the device core for waiting for the
> > iommu controller. Then the workaround can be removed from exynos and mtk
> > iommu drivers. What's the status of IOMMU deferred probe patches?
> 
> I think revisiting probe ordering is now second-from-top on my to-do
> list after this lot. This patch was kind of thinking ahead to get the
> "touch all the drivers" aspect out of the way before it grows any
> bigger, and all the development can then happen in the core code alone,
> but I admit it's not a particularly strong argument.
> 
> > I've encountered a serious problems with current code (the one which
> > instantiates iommu controller devices from iommu driver) and its
> > integration
> > with power domains, clocks and runtime pm, which were not possible to
> > resolve
> > without iommu deferred probe.
> 
> OK. Do you have any plans to try tweaking the current workaround, or is
> it really not worth it? FWIW I do have an Exynos 5410 (Odroid-XU) on my
> desk which I could theoretically test things on, but I suspect it would
> take a fair amount of work to get the SYSMMUs and relevant media bits up
> and running on top of Krzysztof's basic support.
> 
> Will: for the time being, the alternative to this patch would be to
> squash the following change into patch 7/9 (without either, patch 8/9
> doesn't really work).

It's ugly, but I'm fine with it for the moment. No need to wait for the
probe deferral stuff before getting this in.

Will