[3.16.y-ckt stable] Patch "drm/nouveau/fbcon: take runpm reference when userspace has an open fd" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    drm/nouveau/fbcon: take runpm reference when userspace has an open fd

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt20.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 27a1319537ebcc1fdaaa8d0373e52889ed49db8a Mon Sep 17 00:00:00 2001
From: Ben Skeggs <bskeggs at redhat.com>
Date: Fri, 2 Oct 2015 14:03:19 +1000
Subject: drm/nouveau/fbcon: take runpm reference when userspace has an open fd

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,