From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthias Weisser Date: Mon, 13 Jun 2011 15:59:24 +0200 Subject: [U-Boot] newbie questions regarding some config options. In-Reply-To: References: Message-ID: <4DF617BC.4040009@arcor.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Am 13.06.2011 15:09, schrieb PHIL.EDWORTHY at renesas.com: > > Hi Christopher, > >> What is the CONFIG_SYS_TEXT_BASE variable and how can >> I figure out what it should be? > > U-boot is typically stored in flash and one of the first things it does when executed is relocate to ram. CONFIG_SYS_TEXT_BASE is the relocation > address. Typically, u-boot global data, heap and then stack is stored just below this. On ARM, CONFIG_SYS_TEXT_BASE is typically the base address of the image in flash. This is, on a system booting from NOR, the address of the first instruction which is fetched from the CPU. > Since u-boot is used to load some other program like the kernel, you need the u-boot relocation address to be out of the way of this. So, for the > boards I have seen (not arm), CONFIG_SYS_TEXT_BASE is set to the top of ram - 256KB, i.e. enough room for the u-boot image. The relocation address is dynamically calculated from a couple of (runtime) information and has nothing to do with CONFIG_SYS_TEXT_BASE. This is true for ARM and AFAIK for PPC. Matthias