Update stub IOMMU driver (which main purpose is to reuse generic
IOMMU device-tree bindings by Xen grant DMA-mapping layer on Arm)
according to the recent changes done in the following
commit 57365a04c9 ("iommu: Move bus setup to IOMMU device registration").
With probe_device() callback being called during IOMMU device registration,
the uninitialized callback just leads to the "kernel NULL pointer
dereference" issue during boot. Fix that by adding a dummy callback.
Looks like the release_device() callback is not mandatory to be
implemented as IOMMU framework makes sure that callback is initialized
before dereferencing.
Reported-by: Viresh Kumar <viresh.kumar@linaro.org>
Fixes: 57365a04c9 ("iommu: Move bus setup to IOMMU device registration")
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Tested-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/20230208153649.3604857-1-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
In order to reuse generic IOMMU device tree bindings by Xen grant
DMA-mapping layer we need to add this stub driver from a fw_devlink
perspective (grant-dma-ops cannot be converted into the proper
IOMMU driver).
Otherwise, just reusing IOMMU bindings (without having a corresponding
driver) leads to the deferred probe timeout afterwards, because
the IOMMU device never becomes available.
This stub driver does nothing except registering empty iommu_ops,
the upper layer "of_iommu" will treat this as NO_IOMMU condition
and won't return -EPROBE_DEFER.
As this driver is quite different from the most hardware IOMMU
implementations and only needed in Xen guests, place it in drivers/xen
directory. The subsequent commit will make use of it.
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1654197833-25362-7-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>
