[RFC v2 5/8] drm/fb-helper: Don't restore if fbdev is not in use

Noralf Trønnes
2018-01-03T22:21:07Z

Keep track of fbdev users and only restore fbdev in
drm_fb_helper_restore_fbdev_mode_unlocked() when in use. This avoids
fbdev being restored in drm_driver.last_close when nothing uses it.
Additionally fbdev is turned off when the last user is closing.
fbcon is a user in this context.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
drivers/gpu/drm/drm_fb_helper.c | 15 +++++++++++++++
include/drm/drm_fb_helper.h | 14 ++++++++++++++
2 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 2c6adf1d80c2..f9dcc7a5761f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -522,6 +522,9 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
if (READ_ONCE(fb_helper->deferred_setup))
return 0;

+ if (!atomic_read(&fb_helper->open_count))
+ return 0;
+
mutex_lock(&fb_helper->lock);
ret = restore_fbdev_mode(fb_helper);

@@ -781,6 +784,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
INIT_WORK(&helper->resume_work, drm_fb_helper_resume_worker);
INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
helper->dirty_clip.x1 = helper->dirty_clip.y1 = ~0;
+ atomic_set(&helper->open_count, 1);
mutex_init(&helper->lock);
helper->funcs = funcs;
helper->dev = dev;
@@ -1212,6 +1216,7 @@ EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);
* @info: fbdev registered by the helper
* @user: 1=userspace, 0=fbcon
*
+ * Increase fbdev use count.
* If &fb_ops is wrapped in a library, pin the driver module.
*/
int drm_fb_helper_fb_open(struct fb_info *info, int user)
@@ -1224,6 +1229,8 @@ int drm_fb_helper_fb_open(struct fb_info *info, int user)
return -ENODEV;
}

+ atomic_inc(&fb_helper->open_count);
+
return 0;
}
EXPORT_SYMBOL(drm_fb_helper_fb_open);
@@ -1233,6 +1240,7 @@ EXPORT_SYMBOL(drm_fb_helper_fb_open);
* @info: fbdev registered by the helper
* @user: 1=userspace, 0=fbcon
*
+ * Decrease fbdev use count and turn off if there are no users left.
* If &fb_ops is wrapped in a library, unpin the driver module.
*/
int drm_fb_helper_fb_release(struct fb_info *info, int user)
@@ -1240,6 +1248,10 @@ int drm_fb_helper_fb_release(struct fb_info *info, int user)
struct drm_fb_helper *fb_helper = info->par;
struct drm_device *dev = fb_helper->dev;

+ if (atomic_dec_and_test(&fb_helper->open_count) &&
+ !drm_dev_is_unplugged(fb_helper->dev))
+ drm_fb_helper_blank(FB_BLANK_POWERDOWN, info);
+
if (info->fbops->owner != dev->driver->fops->owner)
module_put(dev->driver->fops->owner);

@@ -1936,6 +1948,9 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
if (ret < 0)
return ret;

+ if (fb_helper->fbdev->fbops->fb_open == drm_fb_helper_fb_open)
+ atomic_set(&fb_helper->open_count, 0);
+
strcpy(fb_helper->fb->comm, "[fbcon]");
return 0;
}
diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
index a593f01ff69e..16d8773b60e3 100644
--- a/include/drm/drm_fb_helper.h
+++ b/include/drm/drm_fb_helper.h
@@ -232,6 +232,20 @@ struct drm_fb_helper {
* See also: @deferred_setup
*/
int preferred_bpp;
+
+ /**
+ * @open_count:
+ *
+ * Keeps track of fbdev use to know when to not restore fbdev.
+ *
+ * Drivers that use drm_fb_helper_fb_open() as their \.fb_open
+ * callback will get an initial value of 0 and get restore based on
+ * actual use. Others will get an initial value of 1 which means that
+ * fbdev will always be restored. Drivers that call
+ * drm_fb_helper_fb_open() in their \.fb_open, thus needs to set the
+ * initial value to 0 themselves.
+ */
+ atomic_t open_count;
};

/**
--
2.14.2

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org