[U-Boot] am3517: segmentation fault in Linux after upgrading from arago src to mainline u-boot

[Måns Rullgård]

Yegor Yefremov <yegorslists at googlemail.com> writes:

> On Thu, Nov 28, 2013 at 5:57 PM, Tom Rini <trini at ti.com> wrote:
>> On Thu, Nov 28, 2013 at 05:39:09PM +0100, Yegor Yefremov wrote:
>>
>>> I'm having problems with the new u-boot (November 2013) and am3517
>>> SoC. When I start Debian 7.0 armhf I get lots of Segmentation faults,
>>> I can't even perform apt-get udpate. With the older u-boot (arago
>>> sources from 2010) everything seems to work properly.
>>>
>>> I've checked ATAG_MEM and both u-boot versions deliver same RAM start
>>> address and size. I've compared EMIF4 settings
>>> (arch/arm/cpu/armv7/omap3/emif4.c) and PINMUX and everything is the
>>> same.
>>>
>>> Where else can I look for differences?
>>
>> Can you bisect the arago tree from what it's based on, to what the top
>> of tree is there?  Some errata or another being patched up I guess..
>
> I've compared the x-loader's init routine with the one from SPL. An
> found this workaround in the mainline U-Boot
> (arch/arm/cpu/armv7/omap3/board.c):
>
> static void omap3_setup_aux_cr(void)
> {
>         /* Workaround for Cortex-A8 errata: #454179 #430973
>          *      Set "IBE" bit
>          *      Set "Disable Branch Size Mispredicts" bit
>          * Workaround for erratum #621766
>          *      Enable L1NEON bit
>          * ACR |= (IBE | DBSM | L1NEON) => ACR |= 0xE0
>          */
>         omap3_update_aux_cr_secure(0xE0, 0);
> }
>
> After commenting this routine and I don't see any segmentation faults
> during apt usage.

On an r1pX Cortex-A8 (as found in the 35xx chips) you absolutely want
those bits set, especially if you're running Thumb2 code.  Otherwise you
will get random crashes.

-- 
Måns Rullgård
mans at mansr.com