drm/imx: Use drm_fbdev_generic_setup()

The CMA helper is already using the drm_fb_helper_generic_probe part of
the generic fbdev emulation. This patch makes full use of the generic
fbdev emulation by using its drm_client callbacks. This means that
drm_mode_config_funcs->output_poll_changed and drm_driver->lastclose are
now handled by the emulation code. Additionally fbdev unregister happens
automatically on drm_dev_unregister().

The drm_fbdev_generic_setup() call is put after drm_dev_register() in the
driver. This is done to highlight the fact that fbdev emulation is an
internal client that makes use of the driver, it is not part of the
driver as such. If fbdev setup fails, an error is printed, but the driver
succeeds probing.

CONFIG_DRM_FBDEV_EMULATION wasn't honoured by the CMA helper, but it is by
drm_fb_helper.

Cc: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20180908134648.2582-12-noralf@tronnes.org

drivers/gpu/drm/imx/imx-drm-core.c

@@ -86,7 +86,6 @@ static int imx_drm_atomic_check(struct drm_device *dev,
 
 static const struct drm_mode_config_funcs imx_drm_mode_config_funcs = {
 	.fb_create = drm_gem_fb_create,
-	.output_poll_changed = drm_fb_helper_output_poll_changed,
 	.atomic_check = imx_drm_atomic_check,
 	.atomic_commit = drm_atomic_helper_commit,
 };
@@ -165,7 +164,6 @@ static const struct drm_ioctl_desc imx_drm_ioctls[] = {
 static struct drm_driver imx_drm_driver = {
 	.driver_features	= DRIVER_MODESET | DRIVER_GEM | DRIVER_PRIME |
 				  DRIVER_ATOMIC,
-	.lastclose		= drm_fb_helper_lastclose,
 	.gem_free_object_unlocked = drm_gem_cma_free_object,
 	.gem_vm_ops		= &drm_gem_cma_vm_ops,
 	.dumb_create		= drm_gem_cma_dumb_create,
@@ -263,30 +261,23 @@ static int imx_drm_bind(struct device *dev)
 	 * The fb helper takes copies of key hardware information, so the
 	 * crtcs/connectors/encoders must not change after this point.
 	 */
-#if IS_ENABLED(CONFIG_DRM_FBDEV_EMULATION)
 	if (legacyfb_depth != 16 && legacyfb_depth != 32) {
 		dev_warn(dev, "Invalid legacyfb_depth.  Defaulting to 16bpp\n");
 		legacyfb_depth = 16;
 	}
-	ret = drm_fb_cma_fbdev_init(drm, legacyfb_depth, MAX_CRTC);
-	if (ret)
-		goto err_unbind;
-#endif
 
 	drm_kms_helper_poll_init(drm);
 
 	ret = drm_dev_register(drm, 0);
 	if (ret)
-		goto err_fbhelper;
+		goto err_poll_fini;
+
+	drm_fbdev_generic_setup(drm, legacyfb_depth);
 
 	return 0;
 
-err_fbhelper:
+err_poll_fini:
 	drm_kms_helper_poll_fini(drm);
-#if IS_ENABLED(CONFIG_DRM_FBDEV_EMULATION)
-	drm_fb_cma_fbdev_fini(drm);
-err_unbind:
-#endif
 	component_unbind_all(drm->dev, drm);
 err_kms:
 	drm_mode_config_cleanup(drm);
@@ -303,8 +294,6 @@ static void imx_drm_unbind(struct device *dev)
 
 	drm_kms_helper_poll_fini(drm);
 
-	drm_fb_cma_fbdev_fini(drm);
-
 	drm_mode_config_cleanup(drm);
 
 	component_unbind_all(drm->dev, drm);