[PATCH v2 2/3] drm/cma-helper: Add support for panic screen

[Noralf Trønnes]

Add drm_fb_cma_fb_create() which creates a framebuffer that supports
panic message output.
vmap PRIME buffers on import to support panic on those as well. There
is no atomic way to get a virtual address on a dma_buf.

Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
---
 drivers/gpu/drm/drm_fb_cma_helper.c  | 43 ++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_gem_cma_helper.c |  3 ++
 include/drm/drm_fb_cma_helper.h      |  4 ++-
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
index 5f8074ffe7d9..9d62dadf5d14 100644
--- a/drivers/gpu/drm/drm_fb_cma_helper.c
+++ b/drivers/gpu/drm/drm_fb_cma_helper.c
@@ -56,6 +56,49 @@ struct drm_gem_cma_object *drm_fb_cma_get_gem_obj(struct drm_framebuffer *fb,
 }
 EXPORT_SYMBOL_GPL(drm_fb_cma_get_gem_obj);
 
+static void *drm_fb_cma_fb_panic_vmap(struct drm_framebuffer *fb)
+{
+	return drm_fb_cma_get_gem_obj(fb, 0)->vaddr;
+}
+
+static const struct drm_framebuffer_funcs drm_fb_cma_fb_funcs = {
+	.destroy	= drm_gem_fb_destroy,
+	.create_handle	= drm_gem_fb_create_handle,
+	.panic_vmap	= drm_fb_cma_fb_panic_vmap,
+};
+
+/**
+ * drm_fb_cma_fb_create() - &drm_mode_config_funcs.fb_create callback function
+ * @dev: DRM device
+ * @file: DRM file that holds the GEM handle(s) backing the framebuffer
+ * @mode_cmd: Metadata from the userspace framebuffer creation request
+ *
+ * This function creates a new framebuffer object described by
+ * &drm_mode_fb_cmd2. This description includes handles for the buffer(s)
+ * backing the framebuffer.
+ *
+ * If your hardware has special alignment or pitch requirements these should be
+ * checked before calling this function. The function does buffer size
+ * validation.
+ *
+ * Drivers can use this as their &drm_mode_config_funcs.fb_create callback.
+ * The ADDFB2 IOCTL calls into this callback.
+ *
+ * The &drm_framebuffer_funcs.panic_vmap() callback is set supporting panic
+ * screen rendering.
+ *
+ * Returns:
+ * Pointer to a &drm_framebuffer on success or an error pointer on failure.
+ */
+struct drm_framebuffer *
+drm_fb_cma_fb_create(struct drm_device *dev, struct drm_file *file,
+		     const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
+					    &drm_fb_cma_fb_funcs);
+}
+EXPORT_SYMBOL_GPL(drm_fb_cma_fb_create);
+
 /**
  * drm_fb_cma_get_gem_addr() - Get physical address for framebuffer, for pixel
  * formats where values are grouped in blocks this will get you the beginning of
diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c
index cc26625b4b33..9a4721b5e26d 100644
--- a/drivers/gpu/drm/drm_gem_cma_helper.c
+++ b/drivers/gpu/drm/drm_gem_cma_helper.c
@@ -507,6 +507,9 @@ drm_gem_cma_prime_import_sg_table(struct drm_device *dev,
 	cma_obj->paddr = sg_dma_address(sgt->sgl);
 	cma_obj->sgt = sgt;
 
+	/* Try to vmap the buffer to support panic rendering */
+	cma_obj->vaddr = dma_buf_vmap(attach->dmabuf);
+
 	DRM_DEBUG_PRIME("dma_addr = %pad, size = %zu\n", &cma_obj->paddr, attach->dmabuf->size);
 
 	return &cma_obj->base;
diff --git a/include/drm/drm_fb_cma_helper.h b/include/drm/drm_fb_cma_helper.h
index 4becb09975a4..6c9e5da17140 100644
--- a/include/drm/drm_fb_cma_helper.h
+++ b/include/drm/drm_fb_cma_helper.h
@@ -7,7 +7,9 @@ struct drm_plane_state;
 
 struct drm_gem_cma_object *drm_fb_cma_get_gem_obj(struct drm_framebuffer *fb,
 	unsigned int plane);
-
+struct drm_framebuffer *
+drm_fb_cma_fb_create(struct drm_device *dev, struct drm_file *file,
+		     const struct drm_mode_fb_cmd2 *mode_cmd);
 dma_addr_t drm_fb_cma_get_gem_addr(struct drm_framebuffer *fb,
 				   struct drm_plane_state *state,
 				   unsigned int plane);
-- 
2.20.1