drm/msm: Implement msm drm fb_mmap callback function

This change implements msm drm specific fb_mmap function for fb device
to properly map the fb address to userspace.
Signed-off-by: Hai Li <hali@codeaurora.org>
Signed-off-by: Stephane Viau <sviau@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com> (+ minor comment tweak)

drivers/gpu/drm/msm/msm_fbdev.c

@@ -19,6 +19,11 @@
 
 #include "drm_crtc.h"
 #include "drm_fb_helper.h"
+#include "msm_gem.h"
+
+extern int msm_gem_mmap_obj(struct drm_gem_object *obj,
+					struct vm_area_struct *vma);
+static int msm_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma);
 
 /*
  * fbdev funcs, to implement legacy fbdev interface on top of drm driver
@@ -43,6 +48,7 @@ static struct fb_ops msm_fb_ops = {
 	.fb_fillrect = sys_fillrect,
 	.fb_copyarea = sys_copyarea,
 	.fb_imageblit = sys_imageblit,
+	.fb_mmap = msm_fbdev_mmap,
 
 	.fb_check_var = drm_fb_helper_check_var,
 	.fb_set_par = drm_fb_helper_set_par,
@@ -51,6 +57,31 @@ static struct fb_ops msm_fb_ops = {
 	.fb_setcmap = drm_fb_helper_setcmap,
 };
 
+static int msm_fbdev_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+	struct drm_fb_helper *helper = (struct drm_fb_helper *)info->par;
+	struct msm_fbdev *fbdev = to_msm_fbdev(helper);
+	struct drm_gem_object *drm_obj = fbdev->bo;
+	struct drm_device *dev = helper->dev;
+	int ret = 0;
+
+	if (drm_device_is_unplugged(dev))
+		return -ENODEV;
+
+	mutex_lock(&dev->struct_mutex);
+
+	ret = drm_gem_mmap_obj(drm_obj, drm_obj->size, vma);
+
+	mutex_unlock(&dev->struct_mutex);
+
+	if (ret) {
+		pr_err("%s:drm_gem_mmap_obj fail\n", __func__);
+		return ret;
+	}
+
+	return msm_gem_mmap_obj(drm_obj, vma);
+}
+
 static int msm_fbdev_create(struct drm_fb_helper *helper,
 		struct drm_fb_helper_surface_size *sizes)
 {
@@ -104,8 +135,16 @@ static int msm_fbdev_create(struct drm_fb_helper *helper,
 
 	mutex_lock(&dev->struct_mutex);
 
-	/* TODO implement our own fb_mmap so we don't need this: */
-	msm_gem_get_iova_locked(fbdev->bo, 0, &paddr);
+	/*
+	 * NOTE: if we can be guaranteed to be able to map buffer
+	 * in panic (ie. lock-safe, etc) we could avoid pinning the
+	 * buffer now:
+	 */
+	ret = msm_gem_get_iova_locked(fbdev->bo, 0, &paddr);
+	if (ret) {
+		dev_err(dev->dev, "failed to get buffer obj iova: %d\n", ret);
+		goto fail;
+	}
 
 	fbi = framebuffer_alloc(0, dev->dev);
 	if (!fbi) {
@@ -189,7 +228,7 @@ struct drm_fb_helper *msm_fbdev_init(struct drm_device *dev)
 	struct msm_drm_private *priv = dev->dev_private;
 	struct msm_fbdev *fbdev = NULL;
 	struct drm_fb_helper *helper;
-	int ret = 0;
+	int ret;
 
 	fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
 	if (!fbdev)