drm/omap: dsi: skip dsi_vc_enable_hs when already in correct mode

Simplify and optimize dsi_vc_enable_hs() so that it can be called
without checking the current HS/LP mode. Make dsi_vc_enable_hs() return
if the VC is already in the correct mode.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215104657.802264-69-tomi.valkeinen@ti.com

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

@@ -341,7 +341,6 @@ struct dsi_data {
 	int irq;
 
 	bool is_enabled;
-	bool in_lp_mode;
 
 	struct clk *dss_clk;
 	struct regmap *syscon;
@@ -2443,6 +2442,9 @@ static void dsi_vc_enable_hs(struct omap_dss_device *dssdev, int vc,
 
 	DSSDBG("dsi_vc_enable_hs(%d, %d)\n", vc, enable);
 
+	if (REG_GET(dsi, DSI_VC_CTRL(vc), 9, 9) == enable)
+		return;
+
 	WARN_ON(!dsi_bus_is_locked(dsi));
 
 	dsi_vc_enable(dsi, vc, 0);
@@ -2458,8 +2460,6 @@ static void dsi_vc_enable_hs(struct omap_dss_device *dssdev, int vc,
 	/* start the DDR clock by sending a NULL packet */
 	if (dsi->vm_timings.ddr_clk_always_on && enable)
 		dsi_vc_send_null(dsi, vc, dsi->dsidev->channel);
-
-	dsi->in_lp_mode = !enable;
 }
 
 static void dsi_vc_flush_long_data(struct dsi_data *dsi, int vc)
@@ -4888,9 +4888,7 @@ static ssize_t _omap_dsi_host_transfer(struct dsi_data *dsi, int vc,
 	struct omap_dss_device *dssdev = &dsi->output;
 	int r;
 
-	if (!!(msg->flags & MIPI_DSI_MSG_USE_LPM) != dsi->in_lp_mode)
-		dsi_vc_enable_hs(dssdev, vc,
-				 !(msg->flags & MIPI_DSI_MSG_USE_LPM));
+	dsi_vc_enable_hs(dssdev, vc, !(msg->flags & MIPI_DSI_MSG_USE_LPM));
 
 	switch (msg->type) {
 	case MIPI_DSI_GENERIC_SHORT_WRITE_0_PARAM: