Re: [PATCH] PM OMAP3: Change omap3_save_secure_ram to be called only during init

[Kevin Hilman <khilman@deeprootsystems.com>]

<Tero.Kristo@nokia.com> writes:

>  
>
>>-----Original Message-----
>>From: ext Kevin Hilman [mailto:khilman@deeprootsystems.com]
>>Sent: 13 August, 2009 17:17
>>To: Kristo Tero (Nokia-D/Tampere)
>>Cc: linux-omap@vger.kernel.org
>>Subject: Re: [PATCH] PM OMAP3: Change omap3_save_secure_ram to
>>be called only during init
>>
>>Tero Kristo <tero.kristo@nokia.com> writes:
>>
>>> This function is now called only once during the
>>initialization of the device
>>> and consequent sleep cycles will re-use the same saved
>>contents for secure
>>> RAM. Users who need secure services should do secure RAM
>>saving before
>>> entering off-mode, if a secure service has been accessed
>>after last save.
>>> Signed-off-by: Tero Kristo <tero.kristo@nokia.com>
>>
>>You explain what you're doing, but you don't explain why.
>>
>>Is there a large latency involved in this save/restore that you're
>>trying to eliminate for the no-secure-services case?
>
> There are both latency and reliability issues. The context save uses a
> hardware resource which takes an order of hundreds of milliseconds to
> initialize after a wake up from off-mode, and also there is no way of
> checking whether it is ready from kernel side or not. It just crashes
> if you use it too quickly.

Tero,

OK, makes sense.  Thanks or the clarification.  I'll add this to the
changelog and push to PM branch.

Kevin

>>
>>Kevin
>>
>>> --- arch/arm/mach-omap2/pm34xx.c | 19 ++++++++++++++++++- 1 files
>>> changed, 18 insertions(+), 1 deletions(-)
>>> diff --git a/arch/arm/mach-omap2/pm34xx.c
>>b/arch/arm/mach-omap2/pm34xx.c
>>> index 4223622..b8cf5f2 100644 --- a/arch/arm/mach-omap2/pm34xx.c
>>> +++ b/arch/arm/mach-omap2/pm34xx.c
>>> @@ -127,6 +127,12 @@ static void omap3_core_restore_context(void)
>>> omap_dma_global_context_restore(); }
>>>  
>>> +/* * FIXME: This function should be called before entering
>>off-mode after
>>> + * OMAP3 secure services have been accessed. Currently it
>>is only called
>>> + * once during boot sequence, but this works as we are not
>>using secure
>>> + * services.  */
>>>  static void omap3_save_secure_ram_context(u32 target_mpu_state) {
>>> u32 ret; @@ -349,7 +355,6 @@ void omap_sram_idle(void)
>>> OMAP3_PRM_VOLTCTRL_OFFSET); omap3_core_save_context();
>>> omap3_prcm_save_context(); -
>>> omap3_save_secure_ram_context(mpu_next_state); } /* Enable IO-PAD
>>> wakeup */ prm_set_mod_reg_bits(OMAP3430_EN_IO, WKUP_MOD, PM_WKEN);
>>> @@ -923,6 +928,18 @@ int __init omap3_pm_init(void) }
>>> omap3_save_scratchpad_contents();
>>>  
>>> +	if (omap_type() != OMAP2_DEVICE_TYPE_GP) {
>>> +		local_irq_disable();
>>> +		local_fiq_disable();
>>> +
>>> +		omap_dma_global_context_save();
>>> +		omap3_save_secure_ram_context(PWRDM_POWER_ON);
>>> +		omap_dma_global_context_restore();
>>> +
>>> +		local_irq_enable();
>>> +		local_fiq_enable();
>>> +	}
>>> +
>>>  err1: return ret; err2: -- 1.5.4.3
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>>