Re: [PATCH 3/3] drm/msm: detach the ARM DMA mapping before attaching our own domain
Konrad Dybcio <[email protected]>
| Newsgroups | org.freedesktop.lists.dri-devel,dev.linux.lists.iommu,org.infradead.lists.linux-arm-kernel,org.infradead.lists.linux-rockchip,org.kernel.vger.linux-arm-msm,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
On 7/30/26 3:58 PM, Dmitry Baryshkov wrote:
> On Thu, Jul 30, 2026 at 03:42:58PM +0200, Konrad Dybcio wrote:
>> On 7/30/26 3:29 PM, Dmitry Baryshkov wrote:
>>> On ARM32 with CONFIG_ARM_DMA_USE_IOMMU, arch_setup_dma_ops() creates a
>>> dma_iommu_mapping for every IOMMU-backed device and attaches its domain
>>> to the device's IOMMU group. That domain is neither the group's default
>>> nor its blocking domain, so when msm_iommu_new() later attaches the
>>> domain the driver manages itself, __iommu_attach_group() refuses it:
>>
>> [...]
>>
>>> +#if defined(CONFIG_ARM_DMA_USE_IOMMU)
>>> +#include <asm/dma-iommu.h>
>>> +#else
>>> +#define arm_iommu_detach_device(...) ({ })
>>> +#define arm_iommu_release_mapping(...) ({ })
>>> +#define to_dma_iommu_mapping(dev) NULL
>>> +#endif
>>
>> I see this is prior art, but should we support this config being off?
>
> Yes. For example, on arm64.
Right
Reviewed-by: Konrad Dybcio <[email protected]>
Konrad