linux-kernel - [PATCH 0/2] powernv: Implement lite variant of stop with ESL=EC=0

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Date:   Fri, 16 Sep 2016 15:17:40 +0530
From:   "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Shreyas B. Prabhu" <shreyasbp@...il.com>,
        Michael Neuling <mikey@...ling.org>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Subject: [PATCH 0/2] powernv: Implement lite variant of stop with ESL=EC=0

From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>

Hi,

The Power ISA v3.0 allows us to execute the "stop" instruction with
ESL and EC of the PSSCR set to 0. This will ensure no loss of state,
and the wakeup from the stop will happen at an instruction following
the executed stop instruction.

This patchset adds support to run stop with ESL=EC=0 based on
a flag set for the corresponding stop state in the device tree.

The first patch renames the IDLE_STATE_ENTER_SEQ macro to
IDLE_STATE_ENTER_SEQ_NORET since the current users of this
macro expect the wakeup from stop to happen at the
System Reset vector. It reuses the name IDLE_STATE_ENTER_SEQ to a
variant where the wakeup from stop happens at the next instruction.

The second patch creates adds a new function (i.e, a lite variant)
that will execute a stop instruction with ESL=EC=0 and handle wakeup
at the subsequent instruction. A particular stop state is wired to
this new function if the device tree entry for that stop state has
OPAL_PM_WAKEUP_AT_NEXT_INST [1] flag set.

[1] : The corresponding patch in skiboot that defines
      OPAL_PM_WAKEUP_AT_NEXT_INST and enables it in the device tree
      can be found here:
      https://lists.ozlabs.org/pipermail/skiboot/2016-September/004805.html

Gautham R. Shenoy (2):
  powernv:idle: Add IDLE_STATE_ENTER_SEQ_NORET macro
  powernv:idle:Implement lite variant of power_enter_stop

 arch/powerpc/include/asm/cpuidle.h    |  5 ++++-
 arch/powerpc/include/asm/opal-api.h   |  1 +
 arch/powerpc/include/asm/processor.h  |  3 ++-
 arch/powerpc/kernel/exceptions-64s.S  |  6 +++---
 arch/powerpc/kernel/idle_book3s.S     | 38 +++++++++++++++++++++++++++--------
 arch/powerpc/platforms/powernv/idle.c | 17 +++++++++++++---
 arch/powerpc/platforms/powernv/smp.c  |  2 +-
 drivers/cpuidle/cpuidle-powernv.c     | 24 ++++++++++++++++++++--
 8 files changed, 77 insertions(+), 19 deletions(-)

-- 
1.9.4