On 11/15/2014 10:56 AM, Victor Ascroft wrote:
On 11/15/2014 07:26 AM, Simon Glass wrote:
Hi Albert,
On 14 November 2014 08:26, Albert ARIBAUD albert.u.boot@aribaud.net wrote:
Hello Simon,
On Fri, 14 Nov 2014 07:01:59 -0700, Simon Glass sjg@chromium.org wrote:
Hi Victor,
On 13 November 2014 09:29, Victor Ascroft victorascroft@gmail.com wrote:
Hello,
I am working with a Cortex A5 Freescale Vybrid Processor. Since a thumb build leads to a saving of almost 1 MB for my u-boot image and consequently to faster serial downloads I have been looking at this. Currently enabling this option leads to a hang.
After some debugging I have narrowed the place of hang to "ldr pc, =board_init_r" in arch/arm/lib/crt0.S. My debugging procedure was to put a branch to a small function which just printed a small message with puts, just before the ldr instruction and then a printing a small message with puts just at the start of board_init_r in common/board_r.c . For a non thumb build, the two messages get printed and I can boot to the u-boot prompt. For a thumb build, only the first message before the ldr instruction gets printed.
In crt0.S bl debug_print ldr pc, =board_init_r
In board_init_r puts("In board_init_r\n"); // Right at start
void debug_print(void) { // Defined in board file puts("Debug print\n"); }
My assembly knowledge is limited and after some consultation with a senior colleague, he told me things to check.
An object dump of the crt0.o shows a branch to an even address. For thumb, this is expected to be odd. To just try out, I did a change as below ldr r3, =board_init_r add r3, #1 bx r3
No change with this. My expectation was the compiler/linker/assembler would take care of the requirements, with the CONFIG_SYS_THUMB_BUILD. Frankly speaking I am not sure if this is the complete issue or only a part of it. I have seen patches with regards to OMAP send in by Aneesh V, which made changes of the form .type fn_name, %function to all the low level assembly functions, but, I couldn't dig up much more or variants thereof. Basically, from what I understand, this takes care of specifying .thumb_func for a thumb function or so to speak.
Any pointers?
Victor,
In addition to Simon's question below on the toolchain, I would like to know which commit you're trying to build.
I am using u-boot 2014.10, but, I have a modified branch which supports my hardware and I also have changes for having USB Host and Client support for the Vybrid platform.
The toolchain I am using is gcc-linaro-arm-linux-gnueabihf-2012.09-20120921
http://www.codesourcery.com/public/gnu_toolchain/arm-none-linux-gnueabi/arm-...
http://launchpad.net/linaro-toolchain-binaries/trunk/2012.09/+download/gcc-l...
Sorry I gave the link for the soft floating one by mistake :(.
I have downloaded it from the above link.
I tried this on a peach_pi (Samsung Chromebook 2 13") and it worked OK for me. The code sequence you refer to came out as below for me.
23e01e10 <clbss_l>: 23e01e10: e1500001 cmp r0, r1 23e01e14: 35802000 strcc r2, [r0] 23e01e18: 32800004 addcc r0, r0, #4 23e01e1c: 3afffffb bcc 23e01e10 <clbss_l> 23e01e20: fa000dec blx 23e055d8 <coloured_LED_init> 23e01e24: fb000deb blx 23e055da <red_led_on> 23e01e28: e1a00009 mov r0, r9 23e01e2c: e5991030 ldr r1, [r9, #48] ; 0x30 23e01e30: e59ff008 ldr pc, [pc, #8] ; 23e01e40 <clbss_l+0x30> 23e01e34: 02073800 .word 0x02073800 23e01e38: 23e41eb0 .word 0x23e41eb0 23e01e3c: 23e77bf0 .word 0x23e77bf0 23e01e40: 23e057a9 .word 0x23e057a9
The 'ldr pc' line is loading from 23e01e40 which does have an odd address.
What toolchain are you using? I tried with gcc 4.8.2 - including linaro's 2013.10 release.
In arch/arm/cpu/armv7/config.mk there is a fallback to armv5 from armv7-a, and this may cause it to generate Thumb code instead of Thumb 2. But you should get errors if that happens.
It's hard to debug with such limited visibility. But if I put a puts() at the start of board_init_r(), I see it on the serial console.
Simon,
I believe you've built crt0.S for ARM, not Thumb.
Yes, but I suspect that is a function of the build system. I checked the rest of U-Boot and most of it (including SPL) is Thumb 2. I suppose we could use Thumb 2 for crt0.S if all the instructions are supported.
Yes Simon, you had it for ARM. I also believed it is a function of the build system. But, does crt0.S have to be in Thumb2? Thumb interop is not enough with ARM and Thumb co-existing?
Does CONFIG_SYS_THUMB_BUILD require any specific changes to the build system. I was under the impression, the configuration would take care of it. I can do any changes are required, but, I have no knowledge of it.
Regards, Simon
Regards, Victor.