Re: [PATCH] iommu/exynos: add missing set_platform_dma_ops callback

[Baolu Lu <baolu.lu@linux.intel.com>]

On 2023/2/17 19:08, Marek Szyprowski wrote:
> Hi,
> 
> I'm sorry for a delay in replying, but I was busy with other stuff.
> 
> On 23.01.2023 22:00, Jason Gunthorpe wrote:
>> On Mon, Jan 23, 2023 at 10:31:01AM +0100, Marek Szyprowski wrote:
>>> Add set_platform_dma_ops() required for proper driver operation on ARM
>>> 32bit arch after recent changes in the IOMMU framework (detach ops
>>> removal).
>> Thanks for looking into this!
>>
>> Can you explain more about how this actually solves the problem in the
>> commit message? I don't get it.
> Exynos DRM driver calls arm_iommu_detach_device(), then
> arm_iommu_attach_device() with a difrent 'mapping', see
> drivers/gpu/drm/exynos/exynos_drm_dma.c Lack of set_platform_dma_ops
> leads to a warning in iommu_group_do_set_platform_dma(). The other case
> of calling arm_iommu_detach_device() is after unsuccessful probe of the
> platform device.

Do we really need to call iommu_detach_device() in
arm_iommu_detach_device() for 32-bit ARM? The dma-iommu is disabled for
32-bit ARM, hence calling .set_platform_dma_ops makes no sense.

In below patch,

https://lore.kernel.org/linux-iommu/20230217094736.159005-2-baolu.lu@linux.intel.com/

I removed iommu_detach_device() from arm_iommu_detach_device().

Best regards,
baolu