Re: [PATCH 1/2] ARM: OMAP2+: hwmod data: Fix the wrong clkdm assigned to PRCM modules

["Cousson, Benoit" <b-cousson@ti.com>]

On 6/11/2012 7:26 PM, Paul Walmsley wrote:
> On Mon, 11 Jun 2012, Benoit Cousson wrote:
>
>> The following commit (794b480a37e3d284d6ee7344d8a737ef60476ed5) was adding
>> the PRCM IPs data for PRCM, CM, PRCM_MPU and SCRM.
>> The clkdm entry are not the correct ones and does not exist in the system.
>>
>> Replace them with the proper wkup, l4_ao and l4_cfg.
>
> This does not match either the publicly avaiable documentation and the
> internal NDA hardware specifications[1].

That's almost true, until I realized that the clock domain modules list 
contain this information (clock.py/clock_domain['l4_wkup']['modules']).
Now, I'm wondering as well why this is not documented better. I'll check 
that tomorrow.

> Nor does it make sense from a logical perspective.

I do think it does.

> To take an example from your patch:
>
>> @@ -2564,12 +2543,33 @@ static struct omap_hwmod_rst_info omap44xx_prm_resets[] = {
>>   static struct omap_hwmod omap44xx_prm_hwmod = {
>>   	.name		= "prm",
>>   	.class		= &omap44xx_prcm_hwmod_class,
>> -	.clkdm_name	= "prm_clkdm",
>> +	.clkdm_name	= "l4_wkup_clkdm",
>>   	.mpu_irqs	= omap44xx_prm_irqs,
>>   	.rst_lines	= omap44xx_prm_resets,
>>   	.rst_lines_cnt	= ARRAY_SIZE(omap44xx_prm_resets),
>>   };
>
> There is no possible way that the PRM can exist in the L4_WKUP
> clockdomain.  The L4_WKUP clockdomain must be able to go inactive for the
> chip to enter idle, as we just discussed[1].  But the PRM is the
> entity that supervises chip wakeup from off-mode, so for off-mode
> to work, there's no way that the PRM can be clock-gated.

OK, so let's replace PRM by GPT1, without the part that is not 
applicable in that case:

"There is no possible way that the GPT1 can exist in the L4_WKUP 
clockdomain. The L4_WKUP clockdomain must be able to go inactive for the
chip to enter idle, as we just discussed[1] ... so for off-mode
to work, there's no way that the GPT1 can be clock-gated."

Don't you think that this sentence looks wrong now?
Why can the GPT1 run during OFF mode and not the PRM?

The wkup domain is far from being a standard domain. The 32k is always 
running even in OFF mode. So for the same reason, that domain can go to 
inactive without gating the 32k. This is clearly not a standard domain 
but that does not make it a bad one either.

All the IPs that belongs to the l4_wkup are all active during OFF mode, 
so is the PRM. The point discussed in [1] clearly show that the domain 
inactive state in the case of the wakeup is just used for the OCP clock. 
The functional 32k is still active during OFF mode.

> Frustrating :-(

You should not, I'm happy we were able to figured out where these PRCM 
IPs are located after all these years :-)

>> Fix as well the wrong OCP port used by the cm_core_aon. It uses the
>> l4_cfg interconnect and not the l4_wkup.
>>
>> Re-order the entries by address value.
>
> If you split this part off into a separate patch, I'll take it.

You should take both since this patch is perfectly valid as explained 
previously.

cm_clkdm does not exist either whereas l4_aon / l4_cfg does. And 
honestly considering that the core_cm_aon is inside a domain names 
l4_aon does not seems stupid at all.

The more or less accurate definition of the PRCM clock domain since ever 
is that a domain is mostly a group of IPs and the related clocks that 
does belong to the same interconnect. So it makes sense that the cm_core 
(CM2), cm_core_aon (CM1) and prm does belong to the domain that contains 
its respective interconnect.

Regards,
Benoit


> - Paul
>
> 1. Cousson, Benoît.  _Re: [PATCH] ARM: OMAP2+: hwmod code/data: fix 32K
>     sync timer_.  linux-omap@vger.kernel.org mailing list.  Available from
>     http://www.spinics.net/lists/arm-kernel/msg177128.html (among others).
>


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