drm/panthor: Track the number of mmap on a BO

This will be used to order things by reclaimability.

v2:
- Fix refcounting

v3:
- Fix refcounting (again)

v4:
- Collect R-b

v5:
- Collect R-b

v6:
- Warn on is_imported() (not supposed to happen since mmap is
  redirected to the dmabuf layer) instead of adding a conditional
  in panthor_gem_vm_open()

v7:
- No changes

Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patch.msgid.link/20260401134854.2275433-10-boris.brezillon@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index d9c3a71da29be13048cdfc1403455f4fe1463da3..eb139759beda93bad4d231cda5081859f8539a4a 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -488,6 +488,7 @@ static void panthor_gem_print_info(struct drm_printer *p, unsigned int indent,
        drm_printf_indent(p, indent, "vmap_use_count=%u\n",
                          refcount_read(&bo->cmap.vaddr_use_count));
        drm_printf_indent(p, indent, "vaddr=%p\n", bo->cmap.vaddr);
+       drm_printf_indent(p, indent, "mmap_count=%u\n", refcount_read(&bo->cmap.mmap_count));
 }
 
 static int panthor_gem_pin_locked(struct drm_gem_object *obj)
@@ -604,6 +605,13 @@ static int panthor_gem_mmap(struct drm_gem_object *obj, struct vm_area_struct *v
        if (is_cow_mapping(vma->vm_flags))
                return -EINVAL;
 
+       if (!refcount_inc_not_zero(&bo->cmap.mmap_count)) {
+               dma_resv_lock(obj->resv, NULL);
+               if (!refcount_inc_not_zero(&bo->cmap.mmap_count))
+                       refcount_set(&bo->cmap.mmap_count, 1);
+               dma_resv_unlock(obj->resv);
+       }
+
        vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
        if (should_map_wc(bo))
@@ -740,13 +748,43 @@ static vm_fault_t panthor_gem_fault(struct vm_fault *vmf)
        return panthor_gem_any_fault(vmf, 0);
 }
 
+static void panthor_gem_vm_open(struct vm_area_struct *vma)
+{
+       struct panthor_gem_object *bo = to_panthor_bo(vma->vm_private_data);
+
+       drm_WARN_ON(bo->base.dev, drm_gem_is_imported(&bo->base));
+       drm_WARN_ON(bo->base.dev, !refcount_inc_not_zero(&bo->cmap.mmap_count));
+
+       drm_gem_vm_open(vma);
+}
+
+static void panthor_gem_vm_close(struct vm_area_struct *vma)
+{
+       struct panthor_gem_object *bo = to_panthor_bo(vma->vm_private_data);
+
+       if (drm_gem_is_imported(&bo->base))
+               goto out;
+
+       if (refcount_dec_not_one(&bo->cmap.mmap_count))
+               goto out;
+
+       dma_resv_lock(bo->base.resv, NULL);
+       if (refcount_dec_and_test(&bo->cmap.mmap_count)) {
+               /* Nothing to do, pages are reclaimed lazily. */
+       }
+       dma_resv_unlock(bo->base.resv);
+
+out:
+       drm_gem_object_put(&bo->base);
+}
+
 static const struct vm_operations_struct panthor_gem_vm_ops = {
        .fault = panthor_gem_fault,
 #ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
        .huge_fault = panthor_gem_any_fault,
 #endif
-       .open = drm_gem_vm_open,
-       .close = drm_gem_vm_close,
+       .open = panthor_gem_vm_open,
+       .close = panthor_gem_vm_close,
 };
 
 static const struct drm_gem_object_funcs panthor_gem_funcs = {

diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
index b66478c9590cf328b1b0b7b53e31e6a98efb0592..c0a18dca732c7c86cc5af4d3f11f09ad6e00452d 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_gem.h
+++ b/drivers/gpu/drm/panthor/panthor_gem.h
@@ -80,6 +80,9 @@ struct panthor_gem_cpu_map {
 
        /** @vaddr_use_count: Number of active vmap() requests on this GEM */
        refcount_t vaddr_use_count;
+
+       /** @mmap_count: Number of active mmap() requests on this GEM */
+       refcount_t mmap_count;
 };
 
 /**