linux-kernel - [PATCH] drm/fb_helper: Disable all crtc's when initial setup fails.

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Message-Id: <20171128111603.62757-1-maarten.lankhorst@linux.intel.com>
Date:   Tue, 28 Nov 2017 12:16:03 +0100
From:   Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org, daniel.vetter@...ll.ch,
        Thomas Voegtle <tv@...96.de>, intel-gfx@...ts.freedesktop.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        stable@...r.kernel.org
Subject: [PATCH] drm/fb_helper: Disable all crtc's when initial setup fails.

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")
Cc: <stable@...r.kernel.org> # v4.14+
Reported-by: Thomas Voegtle <tv@...96.de>
---
 drivers/gpu/drm/drm_fb_helper.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 07374008f146..e56166334455 100644
--- 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(struct drm_fb_helper *fb_helper,
 
 	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;
 	}
 
-- 
2.15.0