Hi Albert, On 14 November 2014 08:26, Albert ARIBAUD <albert.u.b...@aribaud.net> wrote: > Hello Simon, > > On Fri, 14 Nov 2014 07:01:59 -0700, Simon Glass <s...@chromium.org> > wrote: >> Hi Victor, >> >> On 13 November 2014 09:29, Victor Ascroft <victorascr...@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 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. Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot