ARM (Thumb Mode) _CPU_Context_switch_arm

[Matthew J Fletcher]

Hi,

I guess it my fault for not 100% copying the rtl22xx BSP into my new
one, i had the cpsr register in a different state at boot_card() time
than the generic ARM context switch code expects. I think that common
binary blob commercial RTOS must do a cpsr read before the first context
switch, rather than rely on a fixed state as i've not encountered this
type of issue before.


On 25 Feb 2013 17:40, "Joel Sherrill" <joel.sherrill at oarcorp.com
<mailto:joel.sherrill at oarcorp.com>> wrote:

    On 2/25/2013 11:25 AM, Matthew J Fletcher wrote:
>     Sebastain,
>
>     I changed the code so now with the cpsr set as expected before
>     main() the context switch occurs fine and we end up in Init().
>
    Is this a generic issue that needs addressing in the RTEMS
    git repo? Or something you broke accidentally when making
    other changes?
>     Thanks for all your help.
>
    A little early for a beer here but it is definitely after 5 for
    Sebastian. Good job Sebastian!

    --joel
>
>     On 25 February 2013 17:10, Matthew J Fletcher <amimjf at gmail.com
>     <mailto:amimjf at gmail.com>> wrote:
>
>         Hi,
>
>         The cpsr thats saved out to r2 is 0x800000df, but is restored
>         back to 0x13. Thanks for pointing out that no cpsr change must
>         happen, i will check how the rtl22xx_t bsp sets up the cpsr.
>
>
>
>         On 25 February 2013 16:52, Sebastian Huber
>         <sebastian.huber at embedded-brains.de
>         <mailto:sebastian.huber at embedded-brains.de>> wrote:
>
>             On 02/25/2013 05:47 PM, Matthew J Fletcher wrote:
>
>                 Hi,
>
>                 r2 is 0x13 before the msr, so I guess new_level must
>                 have been 0.
>
>                 On 25 Feb 2013 15:02, "Sebastian Huber"
>                 <sebastian.huber at embedded-brains.de
>                 <mailto:sebastian.huber at embedded-brains.de>
>                 <mailto:sebastian.huber at embedded-brains.de
>                 <mailto:sebastian.huber at embedded-brains.de>>> wrote:
>
>                     On 02/25/2013 03:15 PM, Matthew J Fletcher wrote:
>
>                         Sebastian,
>
>                         The _Thread_Heir->Registers are ok into the
>                 _Context_Switch() call, sp
>                         and lr
>                         both sensible.
>
>                         At the 'mrs r2, cpsr' line sp is 0x40001b2c
>                 (rubbish) and pc sensible.
>
>                         In _restore, after the 'ldmia r1, ...'
>                 instruction the sp and lr are loaded
>                         with the correct values from
>                 _Thread_Heir->Registers.
>
>                         Its the 'msr cpsr, r2' messes up the sp and lr
>
>
>                     Ok, if you load undefined values into the CPSR,
>                 then a lot of things may
>                     happen.  What is the value of r2 before the msr?
>                  It should be 0x13.
>
>
>             Ok, then maybe the mode in the BSP execution context is
>             wrong.  During _Context_Switch() no mode change must
>             happen.  What is the CPSR before the msr?
>
>             -- 
>             Sebastian Huber, embedded brains GmbH
>
>             Address : Dornierstr. 4, D-82178 Puchheim, Germany
>             Phone   : +49 89 189 47 41-16
>             <tel:%2B49%2089%20189%2047%2041-16>
>             Fax     : +49 89 189 47 41-09
>             <tel:%2B49%2089%20189%2047%2041-09>
>             E-Mail  : sebastian.huber at embedded-brains.de
>             <mailto:sebastian.huber at embedded-brains.de>
>             PGP     : Public key available on request.
>
>             Diese Nachricht ist keine geschäftliche Mitteilung im
>             Sinne des EHUG.
>
>
>
>
>         -- 
>
>         regards
>         ---
>         Matthew J Fletcher
>
>
>
>
>     -- 
>
>     regards
>     ---
>     Matthew J Fletcher
>


    -- 
    Joel Sherrill, Ph.D.             Director of Research & Development 
    joel.sherrill at OARcorp.com <mailto:joel.sherrill at OARcorp.com>        On-Line Applications Research
    Ask me about RTEMS: a free RTOS  Huntsville AL 35805 
    Support Available                (256) 722-9985 

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