[U-Boot] [RFC]: always relocate u-boot before the framebuffer

[Jeroen Hofstee]

Hi All,

Currently CONFIG_FB_ADDR can be set to specify the location of the
frame buffer. Since Linux places the frame buffer at the end of the
RAM, it is nice to place it at the same position so the u-boot to
linux transition can be made flicker free, by preserving the
frame buffer. However u-boot and it's heap prefer to locate themselves
at the end of the RAM as well and there is nothing which prevents them
to overlap.

While this can be set/calculated manually, it would be nicer if the
relocation would never take place to the region occupied by the
frame buffer. A simple way to do so is to locate u-boot before the
frame buffer, like it is already done when the frame buffer address is
not set.

Currently there are 2 boards using the CONFIG_FB_ADDR and CONFIG_LCD
on arm (trats, mimc200). Would it cause any problem to relocate
u-boot below the frame buffer on these boards?

Regards,
Jeroen

proposed patch:

diff --git a/arch/arm/lib/board.c b/arch/arm/lib/board.c
index e0cb635..4d0fc3c 100644
--- a/arch/arm/lib/board.c
+++ b/arch/arm/lib/board.c
@@ -371,9 +371,10 @@ void board_init_f(ulong bootflag)
        gd->fb_base = CONFIG_FB_ADDR;
 #else
        /* reserve memory for LCD display (always full pages) */
-       addr = lcd_setmem(addr);
-       gd->fb_base = addr;
+       gd->fb_base = lcd_setmem(addr);
 #endif /* CONFIG_FB_ADDR */
+       /* always continue placement below the frame buffer to not
overlap */