lkml.org 
[lkml]   [2020]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [RFC 0/3] Integrate Support for self-save and determine
    From
    Date
    Thanks for your comments Ram,
    >> A list of preferred SPRs are maintained in the kernel which contains two
    >> properties:
    >> 1. supported_mode: Helps in identifying if it strictly supports self
    >> save or restore or both.
    > Will be good to capture the information that, 'supported_mode' gets
    > initialized using the information from the device tree.
    >
    >> 2. preferred_mode: Calls out what mode is preferred for each SPR. It
    >> could be strictly self save or restore, or it can also
    >> determine the preference of mode over the other if both
    >> are present by encapsulating the other in bitmask from
    >> LSB to MSB.
    > and 'preferred_mode' is statically initialized.
    >
    Sure thing, I'll mention that.

    >> Below is a table to show the Scenario::Consequence when the self save and
    >> self restore modes are available or disabled in different combinations as
    >> perceived from the device tree thus giving complete backwards compatibly
    >> regardless of an older firmware running a newer kernel or vise-versa.
    >>
    >> SR = Self restore; SS = Self save
    >>
    >> .-----------------------------------.----------------------------------------.
    >> | Scenario | Consequence |
    >> :-----------------------------------+----------------------------------------:
    >> | Legacy Firmware. No SS or SR node | Self restore is called for all |
    >> | | supported SPRs |
    >> :-----------------------------------+----------------------------------------:
    >> | SR: !active SS: !active | Deep stop states disabled |
    >> :-----------------------------------+----------------------------------------:
    >> | SR: active SS: !active | Self restore is called for all |
    >> | | supported SPRs |
    >> :-----------------------------------+----------------------------------------:
    >> | SR: active SS: active | Goes through the preferences for each |
    >> | | SPR and executes of the modes |
    >> | | accordingly. Currently, Self restore is|
    >> | | called for all the SPRs except PSSCR |
    >> | | which is self saved |
    >> :-----------------------------------+----------------------------------------:
    >> | SR: active(only HID0) SS: active | Self save called for all supported |
    >> | | registers expect HID0 (as HID0 cannot |
    >> | | be self saved currently) |
    > Not clear, how this will be conveyed to the hypervisor? Through the
    > device tree or through some other means?
    >
    This information will be conveyed through the device tree. I'll frame a sentence
    that makes this more explicit.

    >> :-----------------------------------+----------------------------------------:
    >> | SR: !active SS: active | currently will disable deep states as |
    >> | | HID0 is needed to be self restored and |
    >> | | cannot be self saved |
    >> '-----------------------------------'----------------------------------------'
    >>
    >> Pratik Rajesh Sampat (3):
    >> powerpc/powernv: Interface to define support and preference for a SPR
    >> powerpc/powernv: Introduce Self save support
    >> powerpc/powernv: Parse device tree, population of SPR support
    >>
    >> arch/powerpc/include/asm/opal-api.h | 3 +-
    >> arch/powerpc/include/asm/opal.h | 1 +
    >> arch/powerpc/platforms/powernv/idle.c | 431 ++++++++++++++++++---
    >> arch/powerpc/platforms/powernv/opal-call.c | 1 +
    >> 4 files changed, 379 insertions(+), 57 deletions(-)
    >>
    >> --
    >> 2.21.0

    \
     
     \ /
      Last update: 2020-01-06 10:46    [W:4.092 / U:0.684 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site