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

[Jean Pihet]

On Thu, Dec 16, 2010 at 1:47 PM, Catalin Marinas
<catalin.marinas at arm.com> wrote:
> 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?
This code is meant to be used by the new DVFS code which is not merged in yet.

Richard, Karthik,
Can you help on that point?

Thanks,
Jean
>
> --
> Catalin
>