SAMA5D4-EK LCDC: Adding a delay after enabling the LCD solves lots of start-up timing issues

arch/arm/src/sama5/sam_lcd.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/sama5/sam_lcd.c
  *
- *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2013-2014 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * References:
@@ -2973,6 +2973,18 @@ int up_fbinitialize(void)
   sam_show_hcr();
 #endif
 
+#if defined(BOARD_LCDC_ENABLE_DELAY) && BOARD_LCDC_ENABLE_DELAY > 0
+  /* Delay a bit after enabling the LDC. I presume that a delay of a few
+   * frame times allows some unstable clocking to synchronize before we
+   * tart thrashing the framebuffer?  But I am not sure why this is
+   * necessary and, in fact, is certainly not necessary in most LCDC
+   * configurations.  Perhaps this delay would not be necessary if timings
+   * were more precise?
+   */
+
+  usleep(BOARD_LCDC_ENABLE_DELAY);
+#endif
+
   /* Enable the backlight.
    *
    * REVISIT:  Backlight level could be dynamically adjustable

configs/sama5d4-ek/include/board.h

@@ -203,6 +203,17 @@
 #define BOARD_LCDC_PIXELCLOCK \
   (BOARD_LCDC_HSPERIOD * BOARD_LCDC_VSPERIOD * BOARD_LCDC_FRAMERATE)
 
+/* This specifies a delay after enabling the LCDC.  This was found
+ * experimentally and is very much a kludge.  I presume that a delay of a
+ * couple of frame times allows some unstable clocking to synchronize before
+ * we start thrashing the framebuffer?  But I am not sure why this is
+ * necessary and, in fact, is certainly not necessary in other LCDC
+ * configurations.  Perhaps the delay would not be necessary if timings were
+ * more precise?
+ */
+
+#define BOARD_LCDC_ENABLE_DELAY (50*1000)
+
 /* Backlight prescaler value and PWM output polarity */
 
 #define BOARD_LCDC_PWMPS      LCDC_LCDCFG6_PWMPS_DIV1