• Gautham R. Shenoy's avatar
    powernv: Pass PSSCR value and mask to power9_idle_stop · 09206b60
    Gautham R. Shenoy authored
    The power9_idle_stop method currently takes only the requested stop
    level as a parameter and picks up the rest of the PSSCR bits from a
    hand-coded macro. This is not a very flexible design, especially when
    the firmware has the capability to communicate the psscr value and the
    mask associated with a particular stop state via device tree.
    
    This patch modifies the power9_idle_stop API to take as parameters the
    PSSCR value and the PSSCR mask corresponding to the stop state that
    needs to be set. These PSSCR value and mask are respectively obtained
    by parsing the "ibm,cpu-idle-state-psscr" and
    "ibm,cpu-idle-state-psscr-mask" fields from the device tree.
    
    In addition to this, the patch adds support for handling stop states
    for which ESL and EC bits in the PSSCR are zero. As per the
    architecture, a wakeup from these stop states resumes execution from
    the subsequent instruction as opposed to waking up at the System
    Vector.
    
    The older firmware sets only the Requested Level (RL) field in the
    psscr and psscr-mask exposed in the device tree. For older firmware
    where psscr-mask=0xf, this patch will set the default sane values that
    the set for for remaining PSSCR fields (i.e PSLL, MTL, ESL, EC, and
    TR). For the new firmware, the patch will validate that the invariants
    required by the ISA for the psscr values are maintained by the
    firmware.
    
    This skiboot patch that exports fully populated PSSCR values and the
    mask for all the stop states can be found here:
    https://lists.ozlabs.org/pipermail/skiboot/2016-September/004869.html
    
    
    
    [Optimize the number of instructions before entering STOP with
    ESL=EC=0, validate the PSSCR values provided by the firimware
    maintains the invariants required as per the ISA suggested by Balbir
    Singh]
    Acked-by: default avatarBalbir Singh <bsingharora@gmail.com>
    Signed-off-by: default avatarGautham R. Shenoy <ego@linux.vnet.ibm.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    09206b60
idle_book3s.S 16.8 KB