[PATCH 3.16.y-ckt 26/94] drm/nouveau/fbcon: take runpm reference when userspace has an open fd

[Luis Henriques]

3.16.7-ckt20 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Skeggs <bskeggs at redhat.com>

commit f231976c2e8964ceaa9250e57d27c35ff03825c2 upstream.

We need to do this in order to prevent accesses to the device while it's
powered down.  Userspace may have an mmap of the fb, and there's no good
way (that I know of) to prevent it from touching the device otherwise.

This fixes some nasty races between runpm and plymouth on some systems,
which result in the GPU getting very upset and hanging the boot.

Signed-off-by: Ben Skeggs <bskeggs at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/gpu/drm/nouveau/nouveau_fbcon.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/nouveau_fbcon.c b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
index f6361391286c..b9d6bf22cc5a 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fbcon.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fbcon.c
@@ -183,8 +183,30 @@ nouveau_fbcon_sync(struct fb_info *info)
 	return 0;
 }
 
+static int
+nouveau_fbcon_open(struct fb_info *info, int user)
+{
+	struct nouveau_fbdev *fbcon = info->par;
+	struct nouveau_drm *drm = nouveau_drm(fbcon->dev);
+	int ret = pm_runtime_get_sync(drm->dev->dev);
+	if (ret < 0 && ret != -EACCES)
+		return ret;
+	return 0;
+}
+
+static int
+nouveau_fbcon_release(struct fb_info *info, int user)
+{
+	struct nouveau_fbdev *fbcon = info->par;
+	struct nouveau_drm *drm = nouveau_drm(fbcon->dev);
+	pm_runtime_put(drm->dev->dev);
+	return 0;
+}
+
 static struct fb_ops nouveau_fbcon_ops = {
 	.owner = THIS_MODULE,
+	.fb_open = nouveau_fbcon_open,
+	.fb_release = nouveau_fbcon_release,
 	.fb_check_var = drm_fb_helper_check_var,
 	.fb_set_par = drm_fb_helper_set_par,
 	.fb_fillrect = nouveau_fbcon_fillrect,
@@ -200,6 +222,8 @@ static struct fb_ops nouveau_fbcon_ops = {
 
 static struct fb_ops nouveau_fbcon_sw_ops = {
 	.owner = THIS_MODULE,
+	.fb_open = nouveau_fbcon_open,
+	.fb_release = nouveau_fbcon_release,
 	.fb_check_var = drm_fb_helper_check_var,
 	.fb_set_par = drm_fb_helper_set_par,
 	.fb_fillrect = cfb_fillrect,