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

[Li Yang]

On Thu, Aug 9, 2012 at 10:52 AM, Jia Hongtao-B38951
<B38951 at freescale.com> wrote:
>
>
>> -----Original Message-----
>> From: Linuxppc-dev [mailto:linuxppc-dev-
>> bounces+b38951=freescale.com at lists.ozlabs.org] On Behalf Of Kumar Gala
>> Sent: Wednesday, August 08, 2012 8:47 PM
>> To: Jia Hongtao-B38951
>> Cc: 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 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 does the PCI code know you're entering deep sleep and not
>> hibernation?
>> >>
>> >> -Scott
>> >
>> > When system come back from hibernation PCI will be initialized again.
>> > So no need to save PCI_CMD and PEXCSRBAR.
>> >
>> > -Hongtao.
>> >
>>
>> What do you mean PCI will be initialized again?  What code path are you
>> talking about that would set PCI_CMD & PEXCSRBAR?
>>
>> - k
>
>
> In hibernation mode:
>
> When system come back from hibernation kernel will start up again.
> Before loading hibernation image PCI initialization has already done.
> Some other hardware also re-init again.

In current Linux implementation, restoring from hibernation image is
using late initcall.  By that time, all the platform devices are
already initialized like a fresh boot.

- Leo