linux-kernel - [PATCH 4.14 79/95] drm/fb_helper: Disable all crtcs when initial setup fails.

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Message-Id: <20171204160049.314698819@linuxfoundation.org>
Date:   Mon,  4 Dec 2017 17:00:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Voegtle <tv@...96.de>,
        Daniel Vetter <daniel.vetter@...ll.ch>
Subject: [PATCH 4.14 79/95] drm/fb_helper: Disable all crtcs when initial setup fails.

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

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

From: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>

commit 52dd06506e9bbc2a37b352df7dfc5468f8da21fd upstream.

Some drivers like i915 start with crtc's enabled, but with deferred
fbcon setup they were no longer disabled as part of fbdev setup.
Headless units could no longer enter pc3 state because the crtc was
still enabled.

Fix this by calling restore_fbdev_mode when we would have called
it otherwise once during initial fbdev setup.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Fixes: ca91a2758fce ("drm/fb-helper: Support deferred setup")
Reported-by: Thomas Voegtle <tv@...96.de>
Tested-by: Thomas Voegtle <tv@...96.de>
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20171128111603.62757-1-maarten.lankhorst@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/drm_fb_helper.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1809,6 +1809,10 @@ static int drm_fb_helper_single_fb_probe
 
 	if (crtc_count == 0 || sizes.fb_width == -1 || sizes.fb_height == -1) {
 		DRM_INFO("Cannot find any crtc or sizes\n");
+
+		/* First time: disable all crtc's.. */
+		if (!fb_helper->deferred_setup && !READ_ONCE(fb_helper->dev->master))
+			restore_fbdev_mode(fb_helper);
 		return -EAGAIN;
 	}