video: ipuv3_fb: skip IPU shutdown if IPU was not enabled before

Boards can skip display interface init using board_video_skip().
If display interface was not initialized (e.g. no ipuv3 framebuffer
registered or IPU clock disabled), booting Linux stops due to the
crash in IPU shutdown function, when accessing IPU registers.
Check IPU clock and skip shutdown if clock is not enabled.
Signed-off-by: NAnatolij Gustschin <agust@denx.de>

drivers/video/mxc_ipuv3_fb.c

@@ -13,6 +13,7 @@
 
 #include <common.h>
 #include <linux/errno.h>
+#include <asm/arch/crm_regs.h>
 #include <asm/global_data.h>
 #include <linux/string.h>
 #include <linux/list.h>
@@ -568,8 +569,18 @@ err0:
 
 void ipuv3_fb_shutdown(void)
 {
-	int i;
+	struct mxc_ccm_reg *mxc_ccm = (struct mxc_ccm_reg *)CCM_BASE_ADDR;
 	struct ipu_stat *stat = (struct ipu_stat *)IPU_STAT;
+	u32 reg;
+	int i;
+
+	/*
+	 * Check if IPU clock was enabled before. Won't access
+	 * IPU registers if clock is not enabled.
+	 */
+	reg = readl(&mxc_ccm->CCGR3);
+	if ((reg & MXC_CCM_CCGR3_IPU1_IPU_MASK) == 0)
+		return;
 
 	for (i = 0; i < ARRAY_SIZE(mxcfb_info); i++) {
 		struct fb_info *fbi = mxcfb_info[i];