drm/rockchip: explain why we can't wait_for_vblanks
Signed-off-by: John Keeping <john@metanate.com>
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@ -176,6 +176,21 @@ static void rockchip_crtc_wait_for_update(struct drm_crtc *crtc)
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crtc_funcs->wait_for_update(crtc);
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crtc_funcs->wait_for_update(crtc);
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}
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}
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/*
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* We can't use drm_atomic_helper_wait_for_vblanks() because rk3288 and rk3066
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* have hardware counters for neither vblanks nor scanlines, which results in
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* a race where:
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* | <-- HW vsync irq and reg take effect
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* plane_commit --> |
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* get_vblank and wait --> |
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* | <-- handle_vblank, vblank->count + 1
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* cleanup_fb --> |
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* iommu crash --> |
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* | <-- HW vsync irq and reg take effect
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*
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* This function is equivalent but uses rockchip_crtc_wait_for_update() instead
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* of waiting for vblank_count to change.
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*/
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static void
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static void
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rockchip_atomic_wait_for_complete(struct drm_device *dev, struct drm_atomic_state *old_state)
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rockchip_atomic_wait_for_complete(struct drm_device *dev, struct drm_atomic_state *old_state)
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{
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{
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