[PATCH 5/6] powerpc/fsl-pci: Add pci inbound/outbound PM support

[Jia Hongtao-B38951]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Thursday, August 09, 2012 5:04 AM
> To: Kumar Gala
> Cc: Jia Hongtao-B38951; Wood Scott-B07421; linuxppc-dev at lists.ozlabs.org;
> Li Yang-R58472
> Subject: Re: [PATCH 5/6] powerpc/fsl-pci: Add pci inbound/outbound PM
> support
> 
> On 08/08/2012 07:46 AM, Kumar Gala wrote:
> >>>>>>>
> >>>>>>> On Jul 24, 2012, at 5:20 AM, Jia Hongtao wrote:
> >>>>>>>
> >>>>>>>> Power supply for PCI inbound/outbound window registers is off
> >>>>>>>> when
> >>>>>>> system
> >>>>>>>> go to deep-sleep state. We save the values of registers before
> >>>>>>>> suspend and restore to registers after resume.
> >>>>>>>>
> >>>>>>>> Signed-off-by: Jiang Yutang <b14898 at freescale.com>
> >>>>>>>> Signed-off-by: Jia Hongtao <B38951 at freescale.com>
> >>>>>>>> Signed-off-by: Li Yang <leoli at freescale.com>
> >>>>>>>> ---
> >>>>>>>> arch/powerpc/include/asm/pci-bridge.h |    2 +-
> >>>>>>>> arch/powerpc/sysdev/fsl_pci.c         |  121
> >>>>>>> +++++++++++++++++++++++++++++++++
> >>>>>>>> 2 files changed, 122 insertions(+), 1 deletions(-)
> >>>>>>>
> >>>>>>> Remind me why we need to save/restore PCI ATMUs, why not just
> >>>>>>> re-parse the device tree to restore?
> >>>>>>>
> >>>>>>> - k
> >>>>>>
> >>>>>> Save/restore is the more efficient way. Latency of sleep/wakeup
> >>>>>> is one of most important features in power management.
> >>>>>>
> >>>>>> -Hongtao.
> >>>>>
> >>>>> I don't think the time it takes to run through setup_pci_atmu() is
> >>>>> that long compared to fsl_pci_resume().
> >>>>>
> >>>>> Also, don't you need to setup PCICCSRBAR and do setup_pci_cmd() on
> >>> resume?
> >>>>>
> >>>>> - k
> >>>>
> >>>> Hi Kumar,
> >>>> I did some tests on P1022DS and found out that PCI_CMD and
> >>>> PCICSRBAR is not lost when system in deep sleep. We don't need to
> save it.
> 
> How do you know you're not just getting lucky?  Maybe it only survives
> deep sleep up to a certain duration, or under other specific
> circumstances.

I tested for more than 10 mins in deep sleep and the result is the same.

> 
> Can you find anywhere that documents what state will be retained during
> deep sleep, or ask an appropriate hardware designer?
> 
> -Scott

I agree with you that we should find out what state will be retained during
deep sleep. But P1022 RM doc has limited information for this. If I can get
more information from hardware designer that will be good.