drm: omapdrm: Check the CRTC software state at enable/disable time

The omapdrm DSS manager enable/disable operations check the DSS manager
state to avoid double enabling/disabling. Check the CRTC software state
instead to decrease the dependency of the DRM layer to the DSS layer.
The dispc_mgr_is_enabled() function then be turned into a static
function, but needs to be moved up in its compilation unit to avoid a
forward declaration.

Add a WARN_ON to catch double enable or disable that should be prevented
by the DRM core and would be a clear sign of a bug. The warning should
eventually be removed.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/dss/dispc.c

@@ -620,6 +620,19 @@ u32 dispc_wb_get_framedone_irq(void)
 	return DISPC_IRQ_FRAMEDONEWB;
 }
 
+void dispc_mgr_enable(enum omap_channel channel, bool enable)
+{
+	mgr_fld_write(channel, DISPC_MGR_FLD_ENABLE, enable);
+	/* flush posted write */
+	mgr_fld_read(channel, DISPC_MGR_FLD_ENABLE);
+}
+EXPORT_SYMBOL(dispc_mgr_enable);
+
+static bool dispc_mgr_is_enabled(enum omap_channel channel)
+{
+	return !!mgr_fld_read(channel, DISPC_MGR_FLD_ENABLE);
+}
+
 bool dispc_mgr_go_busy(enum omap_channel channel)
 {
 	return mgr_fld_read(channel, DISPC_MGR_FLD_GO) == 1;
@@ -2901,20 +2914,6 @@ enum omap_dss_output_id dispc_mgr_get_supported_outputs(enum omap_channel channe
 }
 EXPORT_SYMBOL(dispc_mgr_get_supported_outputs);
 
-void dispc_mgr_enable(enum omap_channel channel, bool enable)
-{
-	mgr_fld_write(channel, DISPC_MGR_FLD_ENABLE, enable);
-	/* flush posted write */
-	mgr_fld_read(channel, DISPC_MGR_FLD_ENABLE);
-}
-EXPORT_SYMBOL(dispc_mgr_enable);
-
-bool dispc_mgr_is_enabled(enum omap_channel channel)
-{
-	return !!mgr_fld_read(channel, DISPC_MGR_FLD_ENABLE);
-}
-EXPORT_SYMBOL(dispc_mgr_is_enabled);
-
 void dispc_wb_enable(bool enable)
 {
 	dispc_ovl_enable(OMAP_DSS_WB, enable);

drivers/gpu/drm/omapdrm/dss/omapdss.h

@@ -856,7 +856,6 @@ int dispc_runtime_get(void);
 void dispc_runtime_put(void);
 
 void dispc_mgr_enable(enum omap_channel channel, bool enable);
-bool dispc_mgr_is_enabled(enum omap_channel channel);
 u32 dispc_mgr_get_vsync_irq(enum omap_channel channel);
 u32 dispc_mgr_get_framedone_irq(enum omap_channel channel);
 u32 dispc_mgr_get_sync_lost_irq(enum omap_channel channel);

drivers/gpu/drm/omapdrm/omap_crtc.c

@@ -135,15 +135,15 @@ static void omap_crtc_set_enabled(struct drm_crtc *crtc, bool enable)
 	u32 framedone_irq, vsync_irq;
 	int ret;
 
+	if (WARN_ON(omap_crtc->enabled == enable))
+		return;
+
 	if (omap_crtc_output[channel]->output_type == OMAP_DISPLAY_TYPE_HDMI) {
 		dispc_mgr_enable(channel, enable);
 		omap_crtc->enabled = enable;
 		return;
 	}
 
-	if (dispc_mgr_is_enabled(channel) == enable)
-		return;
-
 	if (omap_crtc->channel == OMAP_DSS_CHANNEL_DIGIT) {
 		/*
 		 * Digit output produces some sync lost interrupts during the