[Intel-gfx] [PATCH] drm/i915/fbdev: Enable late fbdev initial configuration

[José Roberto de Souza]

If the initial fbdev configuration(intel_fbdev_initial_config()) runs and
there still no sink connected it will cause
drm_fb_helper_initial_config() to return 0 as no error happened(but
internally the return is -EAGAIN).
Because no framebuffer was allocated, when a sink is connected
intel_fbdev_output_poll_changed() will not execute
drm_fb_helper_hotplug_event() that would trigger another try to do the
initial fbdev configuration.

So here creating a dummy framebuffer of 800x600, so
drm_fb_helper_hotplug_event() will be executed and fbdev can be properly
setup when a sink is connected, if needed the dummy framebuffer will be
freed and a new with the proper size will be allocated.

This issue also happens when a MST DP sink is connected since boot, as
the MST topology is discovered in parallel if intel_fbdev_initial_config()
is executed before the first sink MST is discovered it will cause this
same issue.

This is a follow up patch of
https://patchwork.freedesktop.org/patch/196089/

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104158
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104425
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
---
 drivers/gpu/drm/i915/intel_fbdev.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
index 7d41d139341b..773577d39782 100644
--- a/drivers/gpu/drm/i915/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/intel_fbdev.c
@@ -696,14 +696,36 @@ int intel_fbdev_init(struct drm_device *dev)
 	return 0;
 }
 
+static void intel_fbdev_dummy_fb_create(struct intel_fbdev *ifbdev)
+{
+	struct drm_fb_helper_surface_size sizes;
+
+	sizes.fb_width = 800;
+	sizes.fb_height = 600;
+	sizes.surface_width = sizes.fb_width;
+	sizes.surface_height = sizes.fb_height;
+	sizes.surface_bpp = 32;
+	sizes.surface_depth = 24;
+
+	if (intelfb_create(&ifbdev->helper, &sizes))
+		DRM_ERROR("Unable to create dummy framebufer");
+}
+
 static void intel_fbdev_initial_config(void *data, async_cookie_t cookie)
 {
 	struct intel_fbdev *ifbdev = data;
 
 	/* Due to peculiar init order wrt to hpd handling this is separate. */
 	if (drm_fb_helper_initial_config(&ifbdev->helper,
-					 ifbdev->preferred_bpp))
+					 ifbdev->preferred_bpp)) {
 		intel_fbdev_unregister(to_i915(ifbdev->helper.dev));
+		return;
+	}
+
+	mutex_lock(&ifbdev->helper.lock);
+	if (!ifbdev->vma)
+		intel_fbdev_dummy_fb_create(ifbdev);
+	mutex_unlock(&ifbdev->helper.lock);
 }
 
 void intel_fbdev_initial_config_async(struct drm_device *dev)
-- 
2.17.0