Hello,
On 2016-02-17 12:14, Joerg Roedel wrote:
On Wed, Feb 17, 2016 at 08:35:10AM +0100, Marek Szyprowski wrote:
Huh, I wasn't aware of this change in the iommu drivers api. For some
drivers attach/detach callbacks does something more than just programming
page table base register, like for example in case of exynos iommu it is
enabling runtime power management and clocks. The code is really
much simpler
if those calls are balanced, but if the goal is to allow multiple
unballanced
attach calls, I will try to fix this in our driver.
Maybe it should be documented somewhere, that attach calls can be
unbalanced?
Well, when your driver uses default-domains, the detach_dev call-back is
not used anymore. The attach_dev call-back is supposed to just overwrite
any existing binding that may exist for the device. So the calls are not
unbalanced, the detach_dev calls just don't happen anymore.
From driver perspective the default_domains don't really differ from the
'other' domains. They are just allocated from the IOMMU core and used by
the IOMMU/DMA-mapping glue code. That's what I got from reading the code.
There should be also a way to detach the driver even from the default domain
to implement the arch_tear_down_dma_ops function.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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