Re: [PATCH v2 09/13] iommu/rockchip: Use iommu_group_get_for_dev() for add_device

[JeffyChen]

Hi Robin,

On 01/17/2018 08:31 PM, Robin Murphy wrote:
> On 16/01/18 13:25, Jeffy Chen wrote:
> > IOMMU drivers are supposed to call this function instead of manually
> > creating a group in their .add_device callback. This behavior is not
> > strictly required by ARM DMA mapping implementation, but ARM64 already
> > relies on it. This patch fixes the rockchip-iommu driver to comply with
> > this requirement.
>
> FWIW that's not 100% true: what arm64 relies on is the group having a
> default DMA ops domain. Technically, you *could* open-code that in the
> driver's group allocation, but obviously using the appropriate existing
> API is nicer :)
ok, will rewrite the commit message.
> [...]
> > @@ -1182,6 +1164,29 @@ static void rk_iommu_remove_device(struct
> > device *dev)
> >       iommu_group_remove_device(dev);
> >   }
> > +static struct iommu_group *rk_iommu_device_group(struct device *dev)
> > +{
> > +    struct iommu_group *group;
> > +    int ret;
> > +
> > +    group = iommu_group_get(dev);
> > +    if (!group) {
>
> This check is pointless - if dev->iommu_group were non-NULL you wouldn't
> have been called in the first place.
right, it's allocated in the probe.
> Robin.