[PATCH] powerpc/85xx: Save and restore pcie ATMU windows for PM

[Kumar Gala]

On May 20, 2011, at 12:01 AM, Kushwaha Prabhakar-B32579 wrote:

> 
> 
>> -----Original Message-----
>> From: Kumar Gala [mailto:galak at kernel.crashing.org]
>> Sent: Friday, May 20, 2011 10:19 AM
>> To: Kushwaha Prabhakar-B32579
>> Cc: linuxppc-dev at lists.ozlabs.org; meet2prabhu at gmail.com; Jiang Yutang-
>> B14898
>> Subject: Re: [PATCH] powerpc/85xx: Save and restore pcie ATMU windows for
>> PM
>> 
>> 
>> On May 19, 2011, at 11:41 PM, Kushwaha Prabhakar-B32579 wrote:
>> 
>>> 
>>> 
>>>> -----Original Message-----
>>>> From: Kumar Gala [mailto:galak at kernel.crashing.org]
>>>> Sent: Thursday, May 19, 2011 6:53 PM
>>>> To: Kushwaha Prabhakar-B32579
>>>> Cc: linuxppc-dev at lists.ozlabs.org; meet2prabhu at gmail.com; Jiang
>>>> Yutang-
>>>> B14898
>>>> Subject: Re: [PATCH] powerpc/85xx: Save and restore pcie ATMU windows
>>>> for PM
>>>> 
>>>> 
>>>> On May 19, 2011, at 6:22 AM, Kushwaha Prabhakar-B32579 wrote:
>>>> 
>>>>> Hi Kumar,
>>>>> Please find my answer in-lined
>>>>> 
>>>>>> -----Original Message-----
>>>>>> From: Kumar Gala [mailto:galak at kernel.crashing.org]
>>>>>> Sent: Thursday, May 19, 2011 12:00 PM
>>>>>> To: Kushwaha Prabhakar-B32579
>>>>>> Cc: linuxppc-dev at lists.ozlabs.org; meet2prabhu at gmail.com; Jiang
>>>>>> Yutang-
>>>>>> B14898
>>>>>> Subject: Re: [PATCH] powerpc/85xx: Save and restore pcie ATMU
>>>>>> windows for PM
>>>>>> 
>>>>>> 
>>>>>> On Apr 28, 2011, at 1:38 AM, Prabhakar Kushwaha wrote:
>>>>>> 
>>>>>>> D3-cold state indicates removal of the clock and power. however
>>>>>>> auxiliary (AUX) Power may remain available even after the main
>>>>>>> power
>>>>>> rails are powered down.
>>>>>>> 
>>>>>>> wakeup from D3-cold state requires full context restore. Other
>>>>>>> things are taken care in pci-driver except ATMUs.
>>>>>>> ATMU windows needs to be saved and restored during suspend and
>>>> resume.
>>>>>>> 
>>>>>>> Signed-off-by: Jiang Yutang <b14898 at freescale.com>
>>>>>>> Signed-off-by: Prabhakar Kushwaha <prabhakar at freescale.com>
>>>>>>> ---
>>>>>>> Based upon
>>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.g
>>>>>>> it
>>>>>>> (b
>>>>>>> ranch master)
>>>>>>> 
>>>>>>> arch/powerpc/sysdev/fsl_pci.c |  116
>>>>>> +++++++++++++++++++++++++++++++++++++++++
>>>>>>> arch/powerpc/sysdev/fsl_pci.h |    7 ++-
>>>>>>> 2 files changed, 121 insertions(+), 2 deletions(-)
>>>>>> 
>>>>>> Is this patch for when we are a host or agent?
>>>>> 
>>>>> This patch is independent of host or agent. It is for supporting D3
>>>> cold state for P1022.
>>>>> These functions are called during System level suspend and resume.
>>>>> 
>>>>> --Prabhakar
>>>> 
>>>> I'm trying to figure out why this is limited to P1022.
>>> 
>>> Till now, No SOC was supporting D3 cold state. First time P1022
>> supporting it.
>>> Note:  D3 cold state == PCIe block Power down
>>> 
>> 
>> I'm wondering a few things:
>> 
>> 1. Is there any reason not to do this for ALL FSL PCIe SoCs?
> 
> Yes, I am agree with you. It can be done. 
> But as only P1022 SOC supporting it. There is no use of handling it.

I'm also not clear if the DECLARE_PCI_FIXUP_SUSPEND() is the right way for us to connect up these suspend/resume functions.

>> 2. why do bother saving state, we don't we re-parse the .dts and
>> reconfigure ATMUs that way?
> 
> I also thought of this case. But Agent use case scenario forbid me to do this. 
> As ATMU's are programmed by host depending upon different use case . And this information is never stored in the dts.

Fair point, but in agent mode will this code ever really be called?  It seems like we'd never register ourselves with the PCI subsystem so how would this get called?

- k