Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] drm/vc4: dma_free_wc() used with wrong device in vc4_bo_purge() --
commit abd61016c96bce404abb5e31405d8c24a7acfb12 Author: Daniel Drake <[email protected]> drm/vc4: Set DRM DMA device directly from HVS and V3D vc4 uses of_dma_configure() during bind to set the DMA configuration of the drm device by borrowing the configuration of one of its component devices. > diff --git a/drivers/gpu/drm/vc4/vc4_hvs.c b/drivers/gpu/drm/vc4/vc4_hvs.c > index e715147d091ca..305770c87dcf0 100644 > --- a/drivers/gpu/drm/vc4/vc4_hvs.c > +++ b/drivers/gpu/drm/vc4/vc4_hvs.c [ ... ] > @@ -1662,6 +1663,19 @@ static int vc4_hvs_bind(struct device *dev, struct > device *master, void *data) > hvs->regset.nregs = ARRAY_SIZE(vc4_hvs_regs); > } > > + if (vc4->gen >= VC4_GEN_6_C) { > + ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(36)); > + if (ret) > + return ret; > + } > + > + /* > + * Use the HVS as the DRM device's DMA controller for buffer > + * allocations if one has not already been configured. > + */ > + if (drm_dev_dma_dev(drm) == drm->dev) > + drm_dev_set_dma_dev(drm, dev); [Severity: High] Will this change lead to a DMA API regression in vc4_bo_purge()? Looking at drivers/gpu/drm/vc4/vc4_bo.c, when a DMA allocation fails under memory pressure, vc4_bo_userspace_cache_purge() calls vc4_bo_purge() to reclaim memory from BOs marked as DONTNEED. In vc4_bo_purge(), the memory is freed using the virtual aggregate device instead of the newly configured DMA device: static void vc4_bo_purge(struct drm_gem_object *obj) { ... dma_free_wc(dev->dev, obj->size, bo->base.vaddr, bo->base.dma_addr); ... } Since buffer objects are allocated using drm_gem_dma_create(), which now uses the properly configured drm_dev_dma_dev(drm) device, bypassing GEM helpers and explicitly calling dma_free_wc(dev->dev, ...) breaks the DMA API contract. This contract requires memory to be freed with the exact same device pointer used for allocation. Using a different device guarantees IOMMU unmap failures, as the aggregate device no longer has a matching DMA/IOMMU configuration. Should vc4_bo_purge() be updated to use drm_dev_dma_dev(dev) instead of dev->dev? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
