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

[Jason Gunthorpe <jgg@ziepe.ca>]

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.

> diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
> index 6fc58e89712f..c4955d045855 100644
> --- a/drivers/iommu/exynos-iommu.c
> +++ b/drivers/iommu/exynos-iommu.c
> @@ -1346,8 +1346,10 @@ static void exynos_iommu_release_device(struct device *dev)
>  		struct iommu_group *group = iommu_group_get(dev);
>  
>  		if (group) {
> +#ifndef CONFIG_ARM
>  			WARN_ON(owner->domain !=
>  				iommu_group_default_domain(group));
> +#endif
>  			exynos_iommu_detach_device(owner->domain, dev);
>  			iommu_group_put(group);
>  		}
> @@ -1398,6 +1400,9 @@ static int exynos_iommu_of_xlate(struct device *dev,
>  static const struct iommu_ops exynos_iommu_ops = {
>  	.domain_alloc = exynos_iommu_domain_alloc,
>  	.device_group = generic_device_group,
> +#ifdef CONFIG_ARM
> +	.set_platform_dma_ops = exynos_iommu_release_device,
> +#endif

This is ugly, if you need a set_platform_dma_ops it should not be
called release... Release is supposed to be about putting the HW back
to some idle state because we are unplugging the struct device.

Jason