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

[Kumar Gala <galak@kernel.crashing.org>]

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

>=20
>=20
>> -----Original Message-----
>> From: Kumar Gala [mailto:galak@kernel.crashing.org]
>> Sent: Friday, May 20, 2011 10:19 AM
>> To: Kushwaha Prabhakar-B32579
>> Cc: linuxppc-dev@lists.ozlabs.org; meet2prabhu@gmail.com; Jiang =
Yutang-
>> B14898
>> Subject: Re: [PATCH] powerpc/85xx: Save and restore pcie ATMU windows =
for
>> PM
>>=20
>>=20
>> On May 19, 2011, at 11:41 PM, Kushwaha Prabhakar-B32579 wrote:
>>=20
>>>=20
>>>=20
>>>> -----Original Message-----
>>>> From: Kumar Gala [mailto:galak@kernel.crashing.org]
>>>> Sent: Thursday, May 19, 2011 6:53 PM
>>>> To: Kushwaha Prabhakar-B32579
>>>> Cc: linuxppc-dev@lists.ozlabs.org; meet2prabhu@gmail.com; Jiang
>>>> Yutang-
>>>> B14898
>>>> Subject: Re: [PATCH] powerpc/85xx: Save and restore pcie ATMU =
windows
>>>> for PM
>>>>=20
>>>>=20
>>>> On May 19, 2011, at 6:22 AM, Kushwaha Prabhakar-B32579 wrote:
>>>>=20
>>>>> Hi Kumar,
>>>>> Please find my answer in-lined
>>>>>=20
>>>>>> -----Original Message-----
>>>>>> From: Kumar Gala [mailto:galak@kernel.crashing.org]
>>>>>> Sent: Thursday, May 19, 2011 12:00 PM
>>>>>> To: Kushwaha Prabhakar-B32579
>>>>>> Cc: linuxppc-dev@lists.ozlabs.org; meet2prabhu@gmail.com; Jiang
>>>>>> Yutang-
>>>>>> B14898
>>>>>> Subject: Re: [PATCH] powerpc/85xx: Save and restore pcie ATMU
>>>>>> windows for PM
>>>>>>=20
>>>>>>=20
>>>>>> On Apr 28, 2011, at 1:38 AM, Prabhakar Kushwaha wrote:
>>>>>>=20
>>>>>>> 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.
>>>>>>>=20
>>>>>>> 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.
>>>>>>>=20
>>>>>>> Signed-off-by: Jiang Yutang <b14898@freescale.com>
>>>>>>> Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
>>>>>>> ---
>>>>>>> Based upon
>>>>>>> =
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.g
>>>>>>> it
>>>>>>> (b
>>>>>>> ranch master)
>>>>>>>=20
>>>>>>> arch/powerpc/sysdev/fsl_pci.c |  116
>>>>>> +++++++++++++++++++++++++++++++++++++++++
>>>>>>> arch/powerpc/sysdev/fsl_pci.h |    7 ++-
>>>>>>> 2 files changed, 121 insertions(+), 2 deletions(-)
>>>>>>=20
>>>>>> Is this patch for when we are a host or agent?
>>>>>=20
>>>>> 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.
>>>>>=20
>>>>> --Prabhakar
>>>>=20
>>>> I'm trying to figure out why this is limited to P1022.
>>>=20
>>> Till now, No SOC was supporting D3 cold state. First time P1022
>> supporting it.
>>> Note:  D3 cold state =3D=3D PCIe block Power down
>>>=20
>>=20
>> I'm wondering a few things:
>>=20
>> 1. Is there any reason not to do this for ALL FSL PCIe SoCs?
>=20
> Yes, I am agree with you. It can be done.=20
> 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?
>=20
> I also thought of this case. But Agent use case scenario forbid me to =
do this.=20
> 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=