[PATCH v1] drm/rockchip: fix fbdev crash when not use DRM_FBDEV_EMULATION

[Mark Yao]

[    1.162571] Unable to handle kernel NULL pointer dereference at virtual address 00000200
[    1.165656] Modules linked in:
[    1.165941] CPU: 5 PID: 143 Comm: kworker/5:2 Not tainted 4.4.15 #237
[    1.166506] Hardware name: Rockchip RK3399 Evaluation Board v1 (Android) (DT)
[    1.167153] Workqueue: events output_poll_execute
[    1.168231] PC is at mutex_lock+0x14/0x44
[    1.168586] LR is at drm_fb_helper_hotplug_event+0x28/0xcc
[    1.172192] [<ffffff8008982110>] mutex_lock+0x14/0x44
[    1.172196] [<ffffff80084025a4>] drm_fb_helper_hotplug_event+0x28/0xcc
[    1.172201] [<ffffff8008427ae4>] rockchip_drm_output_poll_changed+0x14/0x1c
[    1.172204] [<ffffff80083f7c4c>] drm_kms_helper_hotplug_event+0x28/0x34
[    1.172207] [<ffffff80083f7ddc>] output_poll_execute+0x150/0x198
[    1.172212] [<ffffff80080b0ea8>] process_one_work+0x218/0x3dc
[    1.172215] [<ffffff80080b1578>] worker_thread+0x24c/0x374
[    1.172217] [<ffffff80080b5bcc>] kthread+0xdc/0xe4
[    1.172222] [<ffffff8008084cd0>] ret_from_fork+0x10/0x40

Signed-off-by: Mark Yao <mark.yao at rock-chips.com>
---
Change in v1:
Advised by Daniel Vetter
  only do the struct->pointer conversion alone

 drivers/gpu/drm/rockchip/rockchip_drm_drv.c   |  6 +++---
 drivers/gpu/drm/rockchip/rockchip_drm_drv.h   |  2 +-
 drivers/gpu/drm/rockchip/rockchip_drm_fb.c    |  2 +-
 drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c | 17 ++++++++++-------
 4 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index a822d49..fe22f76 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -261,7 +261,7 @@ static void rockchip_drm_lastclose(struct drm_device *dev)
 {
 	struct rockchip_drm_private *priv = dev->dev_private;
 
-	drm_fb_helper_restore_fbdev_mode_unlocked(&priv->fbdev_helper);
+	drm_fb_helper_restore_fbdev_mode_unlocked(priv->fbdev_helper);
 }
 
 static const struct file_operations rockchip_drm_driver_fops = {
@@ -311,7 +311,7 @@ void rockchip_drm_fb_suspend(struct drm_device *drm)
 	struct rockchip_drm_private *priv = drm->dev_private;
 
 	console_lock();
-	drm_fb_helper_set_suspend(&priv->fbdev_helper, 1);
+	drm_fb_helper_set_suspend(priv->fbdev_helper, 1);
 	console_unlock();
 }
 
@@ -320,7 +320,7 @@ void rockchip_drm_fb_resume(struct drm_device *drm)
 	struct rockchip_drm_private *priv = drm->dev_private;
 
 	console_lock();
-	drm_fb_helper_set_suspend(&priv->fbdev_helper, 0);
+	drm_fb_helper_set_suspend(priv->fbdev_helper, 0);
 	console_unlock();
 }
 
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
index ea39329..f005f3f 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
@@ -57,7 +57,7 @@ struct rockchip_crtc_state {
  * @num_pipe: number of pipes for this device.
  */
 struct rockchip_drm_private {
-	struct drm_fb_helper fbdev_helper;
+	struct drm_fb_helper *fbdev_helper;
 	struct drm_gem_object *fbdev_bo;
 	const struct rockchip_crtc_funcs *crtc_funcs[ROCKCHIP_MAX_CRTC];
 	struct drm_atomic_state *state;
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
index 55c5273..dc034ec 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
@@ -156,7 +156,7 @@ err_gem_object_unreference:
 static void rockchip_drm_output_poll_changed(struct drm_device *dev)
 {
 	struct rockchip_drm_private *private = dev->dev_private;
-	struct drm_fb_helper *fb_helper = &private->fbdev_helper;
+	struct drm_fb_helper *fb_helper = private->fbdev_helper;
 
 	if (fb_helper)
 		drm_fb_helper_hotplug_event(fb_helper);
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c b/drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c
index 207e01d..6b50dfa 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c
@@ -22,14 +22,12 @@
 #include "rockchip_drm_fb.h"
 
 #define PREFERRED_BPP		32
-#define to_drm_private(x) \
-		container_of(x, struct rockchip_drm_private, fbdev_helper)
 
 static int rockchip_fbdev_mmap(struct fb_info *info,
 			       struct vm_area_struct *vma)
 {
 	struct drm_fb_helper *helper = info->par;
-	struct rockchip_drm_private *private = to_drm_private(helper);
+	struct rockchip_drm_private *private = helper->dev->dev_private;
 
 	return rockchip_gem_mmap_buf(private->fbdev_bo, vma);
 }
@@ -50,7 +48,7 @@ static struct fb_ops rockchip_drm_fbdev_ops = {
 static int rockchip_drm_fbdev_create(struct drm_fb_helper *helper,
 				     struct drm_fb_helper_surface_size *sizes)
 {
-	struct rockchip_drm_private *private = to_drm_private(helper);
+	struct rockchip_drm_private *private = helper->dev->dev_private;
 	struct drm_mode_fb_cmd2 mode_cmd = { 0 };
 	struct drm_device *dev = helper->dev;
 	struct rockchip_gem_object *rk_obj;
@@ -139,7 +137,11 @@ int rockchip_drm_fbdev_init(struct drm_device *dev)
 
 	num_crtc = dev->mode_config.num_crtc;
 
-	helper = &private->fbdev_helper;
+	helper = devm_kzalloc(dev->dev, sizeof(*helper), GFP_KERNEL);
+	if (!helper)
+		return -ENOMEM;
+
+	private->fbdev_helper = helper;
 
 	drm_fb_helper_prepare(dev, helper, &rockchip_drm_fb_helper_funcs);
 
@@ -173,9 +175,10 @@ err_drm_fb_helper_fini:
 void rockchip_drm_fbdev_fini(struct drm_device *dev)
 {
 	struct rockchip_drm_private *private = dev->dev_private;
-	struct drm_fb_helper *helper;
+	struct drm_fb_helper *helper = private->fbdev_helper;
 
-	helper = &private->fbdev_helper;
+	if (!helper)
+		return;
 
 	drm_fb_helper_unregister_fbi(helper);
 	drm_fb_helper_release_fbi(helper);
-- 
1.9.1