video: fsl_dcu_fb: fix framebuffer to the end of memory

Fix the framebuffer location to the very end of the available memory.
This allows to remove the area from available memory for the kernel,
which in turn allows to display the splash screen through the Linux
kernel boot process.

Ideas has been taken from the sunxi display driver, e.g.
20779ec3a5 ("sunxi: video: Dynamically reserve framebuffer memory")

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>

drivers/video/Kconfig

@@ -402,6 +402,14 @@ config VIDEO_FSL_DCU_FB
 	 This enables support for Freescale Display Control Unit (DCU4)
 	 module found on Freescale Vybrid and QorIQ family of SoCs.
 
+config VIDEO_FSL_DCU_MAX_FB_SIZE_MB
+	int "Freescale DCU framebuffer size"
+	depends on VIDEO_FSL_DCU_FB
+	default 4194304
+	help
+	 Set maximum framebuffer size to be used for Freescale Display
+	 Controller Unit (DCU4).
+
 config VIDEO_ROCKCHIP
 	bool "Enable Rockchip video support"
 	depends on DM_VIDEO

drivers/video/fsl_dcu_fb.c

@@ -8,6 +8,7 @@
 
 #include <asm/io.h>
 #include <common.h>
+#include <fdt_support.h>
 #include <fsl_dcu_fb.h>
 #include <linux/fb.h>
 #include <malloc.h>
@@ -79,6 +80,8 @@
 #define BPP_24_RGB888			5
 #define BPP_32_ARGB8888			6
 
+DECLARE_GLOBAL_DATA_PTR;
+
 /*
  * This setting is used for the TWR_LCD_RGB card
  */
@@ -254,11 +257,19 @@ int fsl_dcu_init(unsigned int xres, unsigned int yres,
 	struct dcu_reg *regs = (struct dcu_reg *)CONFIG_SYS_DCU_ADDR;
 	unsigned int div, mode;
 
-	/* Memory allocation for framebuffer */
 	info.screen_size =
 		info.var.xres * info.var.yres * (info.var.bits_per_pixel / 8);
-	info.screen_base = (char *)memalign(ARCH_DMA_MINALIGN,
+
-			roundup(info.screen_size, ARCH_DMA_MINALIGN));
+	if (info.screen_size > CONFIG_VIDEO_FSL_DCU_MAX_FB_SIZE_MB) {
+		info.screen_size = 0;
+		return -ENOMEM;
+	}
+
+	/* Reserve framebuffer at the end of memory */
+	gd->fb_base = gd->bd->bi_dram[0].start +
+			gd->bd->bi_dram[0].size - info.screen_size;
+	info.screen_base = (char *)gd->fb_base;
+
 	memset(info.screen_base, 0, info.screen_size);
 
 	reset_total_layers();
@@ -305,6 +316,11 @@ int fsl_dcu_init(unsigned int xres, unsigned int yres,
 	return 0;
 }
 
+ulong board_get_usable_ram_top(ulong total_size)
+{
+	return gd->ram_top - CONFIG_VIDEO_FSL_DCU_MAX_FB_SIZE_MB;
+}
+
 void *video_hw_init(void)
 {
 	static GraphicDevice ctfb;
@@ -363,3 +379,26 @@ void *video_hw_init(void)
 
 	return &ctfb;
 }
+
+#if defined(CONFIG_OF_BOARD_SETUP)
+int fsl_dcu_fixedfb_setup(void *blob)
+{
+	u64 start, size;
+	int ret;
+
+	start = gd->bd->bi_dram[0].start;
+	size = gd->bd->bi_dram[0].size - info.screen_size;
+
+	/*
+	 * Align size on section size (1 MiB).
+	 */
+	size &= 0xfff00000;
+	ret = fdt_fixup_memory_banks(blob, &start, &size, 1);
+	if (ret) {
+		eprintf("Cannot setup fb: Error reserving memory\n");
+		return ret;
+	}
+
+	return 0;
+}
+#endif

include/fsl_dcu_fb.h

@@ -9,6 +9,7 @@
 
 int fsl_dcu_init(unsigned int xres, unsigned int yres,
 		 unsigned int pixel_format);
+int fsl_dcu_fixedfb_setup(void *blob);
 
 /* Prototypes for external board-specific functions */
 int platform_dcu_init(unsigned int xres, unsigned int yres,