OMAP3: Warning: swp{b} use is deprecated for this architecture

[Catalin Marinas]

On 16 December 2010 11:56, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> On Thu, Dec 16, 2010 at 12:49:43PM +0100, Jean Pihet wrote:
>> The following warning is issued by the compiler (gcc version 4.4.1
>> (Sourcery G++ Lite 2010q1-202):
>> arch/arm/mach-omap2/sleep34xx.S:87: Warning: swp{b} use is deprecated
>> for this architecture
>>
>> Does this need fixing? If so any hint on how to do it?
>>
>> Here is the offending code excerpt:
>>
>> wait_sem:
>>         mov     r0,#1
>>         ldr     r1, sdrc_scratchpad_sem
>> wait_loop:
>>         ldr     r2, [r1]        @ load the lock value
>>         cmp     r2, r0          @ is the lock free ?
>>         beq     wait_loop       @ not free...
>>         swp     r2, r0, [r1]    @ semaphore free so lock it and proceed
>>         cmp     r2, r0          @ did we succeed ?
>>         beq     wait_sem        @ no - try again
>
> (untested, as my LDP is useless because of OMAP regressions.)
>
> wait_sem:
>        mov     r0, #1
>        ldr     r1, sdrc_scratchpad_sem
> wait_loop:
>        ldrex   r2, [r1]        @ load lock value
>        teq     r2, r0          @ is lock free ( != 1)
>        beq     wait_loop       @ no, try again
>        strex   r2, r0, [r1]    @ try to lock
>        teq     r2, #0          @ did store succeed?
>        bne     wait_loop       @ no, try again

I'm not familiar with the OMAP code but I recall they needed swp for
some synchronisation with external processor (DSP). Is this still the
case?

-- 
Catalin