drm/mediatek: Implement gem prime vmap/vunmap function

For some application which need kernel virtual address, such as fbcon,
implement these function to map/unmap kernel virtual address of prime
buffer.
Signed-off-by: CK Hu <ck.hu@mediatek.com>

drivers/gpu/drm/mediatek/mtk_drm_drv.c

@@ -341,6 +341,8 @@ static struct drm_driver mtk_drm_driver = {
 	.gem_prime_get_sg_table = mtk_gem_prime_get_sg_table,
 	.gem_prime_import_sg_table = mtk_gem_prime_import_sg_table,
 	.gem_prime_mmap = mtk_drm_gem_mmap_buf,
+	.gem_prime_vmap = mtk_drm_gem_prime_vmap,
+	.gem_prime_vunmap = mtk_drm_gem_prime_vunmap,
 	.fops = &mtk_drm_fops,
 
 	.name = DRIVER_NAME,

drivers/gpu/drm/mediatek/mtk_drm_gem.c

@@ -241,3 +241,49 @@ struct drm_gem_object *mtk_gem_prime_import_sg_table(struct drm_device *dev,
 	kfree(mtk_gem);
 	return ERR_PTR(ret);
 }
+
+void *mtk_drm_gem_prime_vmap(struct drm_gem_object *obj)
+{
+	struct mtk_drm_gem_obj *mtk_gem = to_mtk_gem_obj(obj);
+	struct sg_table *sgt;
+	struct sg_page_iter iter;
+	unsigned int npages;
+	unsigned int i = 0;
+
+	if (mtk_gem->kvaddr)
+		return mtk_gem->kvaddr;
+
+	sgt = mtk_gem_prime_get_sg_table(obj);
+	if (IS_ERR(sgt))
+		return NULL;
+
+	npages = obj->size >> PAGE_SHIFT;
+	mtk_gem->pages = kcalloc(npages, sizeof(*mtk_gem->pages), GFP_KERNEL);
+	if (!mtk_gem->pages)
+		goto out;
+
+	for_each_sg_page(sgt->sgl, &iter, sgt->orig_nents, 0) {
+		mtk_gem->pages[i++] = sg_page_iter_page(&iter);
+		if (i > npages)
+			break;
+	}
+	mtk_gem->kvaddr = vmap(mtk_gem->pages, npages, VM_MAP,
+			       pgprot_writecombine(PAGE_KERNEL));
+
+out:
+	kfree((void *)sgt);
+
+	return mtk_gem->kvaddr;
+}
+
+void mtk_drm_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
+{
+	struct mtk_drm_gem_obj *mtk_gem = to_mtk_gem_obj(obj);
+
+	if (!mtk_gem->pages)
+		return;
+
+	vunmap(vaddr);
+	mtk_gem->kvaddr = 0;
+	kfree((void *)mtk_gem->pages);
+}

drivers/gpu/drm/mediatek/mtk_drm_gem.h

@@ -37,6 +37,7 @@ struct mtk_drm_gem_obj {
 	dma_addr_t		dma_addr;
 	unsigned long		dma_attrs;
 	struct sg_table		*sg;
+	struct page		**pages;
 };
 
 #define to_mtk_gem_obj(x)	container_of(x, struct mtk_drm_gem_obj, base)
@@ -52,5 +53,7 @@ int mtk_drm_gem_mmap_buf(struct drm_gem_object *obj,
 struct sg_table *mtk_gem_prime_get_sg_table(struct drm_gem_object *obj);
 struct drm_gem_object *mtk_gem_prime_import_sg_table(struct drm_device *dev,
 			struct dma_buf_attachment *attach, struct sg_table *sg);
+void *mtk_drm_gem_prime_vmap(struct drm_gem_object *obj);
+void mtk_drm_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr);
 
 #endif