From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Date: Thu, 14 Jan 2016 12:27:02 -0700 Subject: [U-Boot] [U-Boot, v7, 2/2] arm: move gd handling outside of C code In-Reply-To: <20160114191158.GM3359@bill-the-cat> References: <1448470593-23998-2-git-send-email-albert.u.boot@aribaud.net> <20160114132044.GE3359@bill-the-cat> <5697EA7B.8000204@wwwdotorg.org> <20160114191158.GM3359@bill-the-cat> Message-ID: <5697F686.7010707@wwwdotorg.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 01/14/2016 12:11 PM, Tom Rini wrote: > On Thu, Jan 14, 2016 at 11:35:39AM -0700, Stephen Warren wrote: >> On 01/14/2016 06:20 AM, Tom Rini wrote: >>> On Wed, Nov 25, 2015 at 05:56:33PM +0100, Albert ARIBAUD wrote: >>> >>>> As of gcc 5.2.1 for Thumb-1, it is not possible any >>>> more to assign gd from C code, as gd is mapped to r9, >>>> and r9 may now be saved in the prolog sequence, and >>>> restored in the epilog sequence, of any C functions. >>>> >>>> Therefore arch_setup_gd(), which is supposed to set >>>> r9, may actually have no effect, causing U-Boot to >>>> use a bad address to access GD. >>>> >>>> Fix this by never calling arch_setup_gd() for ARM, >>>> and instead setting r9 in arch/arm/lib/crt0.S, to >>>> the value returned by board_init_f_alloc_reserve(). >>>> >>>> Signed-off-by: Albert ARIBAUD >>>> Reviewed-by: Simon Glass >>> >>> Applied to u-boot/master, thanks! >> >> FYI, this commit causes U-Boot to fail (crash or hang during very >> early startup with zero UART output) on at least an NVIDIA Jetson >> TX1 (p2371-2180) board. Reverting just this in u-boot/master solves >> the issue. I have not tested other boards or looked at the code >> itself yet. > > Is that one of the systems where we have an ARM9 and then a Cortex-A? > FWIW, my pandaboard is up in Fedora currently. I'm trying to do some > boot testing on what I have more often and then a bigger round of > unboxing and testing at -rc1/release time. This board is AArch64. There's no SPL or dual-architecture U-Boot on this system; a boot CPU runs the boot ROM and and NVIDIA binary bootloader which loads U-Boot from disk and sets up the main CPU, then the main ARM CPU essentially jumps straight into the main U-Boot binary. For more precise details, see: ftp://download.nvidia.com/tegra-public-appnotes/t210-nvtboot-flow.html or a bunch of stuff accessible from the following for more background: ftp://download.nvidia.com/tegra-public-appnotes/index.html