[PATCH 14/25] OMAP4: PM: Add CPUX OFF mode support

[Shilimkar, Santosh]

IOn Sat, Sep 10, 2011 at 5:04 AM, Shawn Guo <shawn.guo at freescale.com> wrote:
> On Fri, Sep 09, 2011 at 10:29:49PM +0530, Santosh wrote:
>> On Friday 09 September 2011 08:57 PM, Shawn Guo wrote:
>> >On Fri, Sep 09, 2011 at 07:41:08PM +0530, Shilimkar, Santosh wrote:
>> >>On Fri, Sep 9, 2011 at 7:43 PM, Shawn Guo<shawn.guo at freescale.com>  wrote:
>> >>>On Fri, Sep 09, 2011 at 01:39:51PM +0530, Santosh wrote:
>> >>>>On Friday 09 September 2011 01:34 PM, Shawn Guo wrote:
>> >>>>>Hi Santosh,
>>
>> [...]
>>
>> >>#ifdef CONFIG_CACHE_L2X0
>> >>    /*
>> >>     * Clean and invalidate the L2 cache.
>> >>     * Common cache-l2x0.c functions can't be used here since it
>> >>     * uses spinlocks. We are out of coherency here with data cache
>> >>     * disabled. The spinlock implementation uses exclusive load/store
>> >>     * instruction which can fail without data cache being enabled.
>> >>     * OMAP4 hardware doesn't support exclusive monitor which can
>> >>     * overcome exclusive access issue. Because of this, CPU can
>> >>     * lead to deadlock.
>> >>     */
>> >>l2x_clean_inv:
>> >>    bl      omap4_get_sar_ram_base
>> >>    mov     r8, r0
>> >>    mrc     p15, 0, r5, c0, c0, 5           @ Read MPIDR
>> >>    ands    r5, r5, #0x0f
>> >>    ldreq   r0, [r8, #L2X0_SAVE_OFFSET0]
>> >>    ldrne   r0, [r8, #L2X0_SAVE_OFFSET1]
>> >>    cmp     r0, #3
>> >>    bne     do_WFI
>> >
>> >It looks like you are bypassing L2 clean and invalidate for cases
>> >"1" and "2" here.  But I really do not understand how you get r0
>> >back here.
>> >
>> The value which is passed in R0 is also stored in scratch patch memory
>> and retrieved using L2X0_SAVE_OFFSET0.
>> Simple :)
>>
> Aha, no wonder that I read it wrongly.  The parameter passing in r0
> is here simply for confusing people.
>
No It's not. Same cod is used for CPUIDLE and we do have different
C-states than just OSWR. ON and INACTIVE makes use of it.

> Also, IMO, lable "l2x_clean_inv" should be put after the "bne do_WFI".
> Otherwise, my original statement (it seems l2x_clean_inv will be
> called for case "2") stands correct :)
>
It's just a label. All L2 related code and checks for the valid state is
kept under that by purpose.

Regards
Santosh