drm/tidss: Soft Reset DISPC on startup

Soft reset the display subsystem controller on startup and wait for
the reset to complete. This helps the scenario where display was
already in use by some other core before the linux was booted.

Signed-off-by: Devarsh Thakkar <devarsht@ti.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220314113739.18000-1-devarsht@ti.com

drivers/gpu/drm/tidss/tidss_dispc.c

@@ -2650,6 +2650,20 @@ static void dispc_init_errata(struct dispc_device *dispc)
 	}
 }
 
+static void dispc_softreset(struct dispc_device *dispc)
+{
+	u32 val;
+	int ret = 0;
+
+	/* Soft reset */
+	REG_FLD_MOD(dispc, DSS_SYSCONFIG, 1, 1, 1);
+	/* Wait for reset to complete */
+	ret = readl_poll_timeout(dispc->base_common + DSS_SYSSTATUS,
+				 val, val & 1, 100, 5000);
+	if (ret)
+		dev_warn(dispc->dev, "failed to reset dispc\n");
+}
+
 int dispc_init(struct tidss_device *tidss)
 {
 	struct device *dev = tidss->dev;
@@ -2709,6 +2723,10 @@ int dispc_init(struct tidss_device *tidss)
 			return r;
 	}
 
+	/* K2G display controller does not support soft reset */
+	if (feat->subrev != DISPC_K2G)
+		dispc_softreset(dispc);
+
 	for (i = 0; i < dispc->feat->num_vps; i++) {
 		u32 gamma_size = dispc->feat->vp_feat.color.gamma_size;
 		u32 *gamma_table;