drm/verisilicon: unconditionally use the DC device as dma_dev

[Icenowy]

As the display-subsystem is outside of the soc device tree node (where the dma-noncoherent property is added), it's assumed to be coherent, and lead to allocated memory being not properly mapped (still cached).

Unconditionally use the DC device (which is in the soc node) as dma_dev to fix framebuffer mapping issue.

Summary by Sourcery

Always use the DC device as the DMA device in Verisilicon DRM to ensure proper framebuffer mapping and reflect that change in function naming.

Bug Fixes:

• Fix framebuffer mapping by unconditionally assigning the DC device as dma_dev

Enhancements:

• Rename vs_drm_iommu_attach_device/detach_device to vs_drm_dma_attach_device/detach_device
• Update DC binding code and error messages to use the new DMA attach/detach APIs and unconditionally set/reset priv->dma_dev

[sourcery-ai]

Reviewer's Guide

This PR ensures the DC device is always used as the DMA device by assigning dma_dev before any IOMMU checks and refining detach logic, renames the IOMMU-specific attach/detach APIs to reflect DMA semantics, and updates the DC driver to invoke the new DMA functions with corrected log messages.

Class diagram for updated DMA attach/detach API in Verisilicon DRM driver

classDiagram
    class vs_drm_private {
        +struct device *dma_dev
        +struct iommu_domain *domain
        +unsigned int pitch_alignment
    }
    class drm_device {
        +void *dev_private
        +struct device *dev
    }
    vs_drm_private <.. drm_device : dev_private

    class vs_drm_dma_attach_device {
        +int vs_drm_dma_attach_device(struct drm_device *drm_dev, struct device *dev)
    }
    class vs_drm_dma_detach_device {
        +void vs_drm_dma_detach_device(struct drm_device *drm_dev, struct device *dev)
    }
    drm_device <.. vs_drm_dma_attach_device
    drm_device <.. vs_drm_dma_detach_device

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Class diagram for DC device binding and DMA device assignment

classDiagram
    class dc_bind {
        +int dc_bind(struct device *dev, struct device *master, void *data)
    }
    class dc_unbind {
        +void dc_unbind(struct device *dev, struct device *master, void *data)
    }
    class vs_drm_dma_attach_device {
        +int vs_drm_dma_attach_device(struct drm_device *drm_dev, struct device *dev)
    }
    class vs_drm_dma_detach_device {
        +void vs_drm_dma_detach_device(struct drm_device *drm_dev, struct device *dev)
    }
    dc_bind --> vs_drm_dma_attach_device : calls
    dc_unbind --> vs_drm_dma_detach_device : calls

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File-Level Changes

Change	Details	Files
Unconditionally use DC device as dma_dev	Assign priv->dma_dev before IOMMU check in attach Remove redundant dma_dev assignment inside IOMMU block Move dma_dev reset to before IOMMU detach and guard by matching device	drivers/gpu/drm/verisilicon/vs_drv.c
Rename IOMMU attach/detach functions to DMA semantics	Rename vs_drm_iommu_attach_device to vs_drm_dma_attach_device Rename vs_drm_iommu_detach_device to vs_drm_dma_detach_device Update function prototypes in vs_drv.h	drivers/gpu/drm/verisilicon/vs_drv.c drivers/gpu/drm/verisilicon/vs_drv.h
Update DC driver to use renamed DMA functions	Replace vs_drm_iommu_* calls with vs_drm_dma_* in dc_bind/dc_unbind Adjust dev_err message to reference DMA device	drivers/gpu/drm/verisilicon/vs_dc.c

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[sourcery-ai]

Hey @Icenowy - I've reviewed your changes and they look great!

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