linux-kernel - [PATCH v3 0/3] cpuidle-pseries: Parse extended CEDE information for idle.

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Date:   Thu, 30 Jul 2020 11:02:54 +0530
From:   "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
To:     Nicholas Piggin <npiggin@...il.com>,
        Anton Blanchard <anton@...abs.org>,
        Nathan Lynch <nathanl@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org,
        "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Subject: [PATCH v3 0/3] cpuidle-pseries: Parse extended CEDE information for idle.

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

This is a v3 of the patch series to parse the extended CEDE
information in the pseries-cpuidle driver.

The previous two versions of the patches can be found here:

v2: https://lore.kernel.org/lkml/1596005254-25753-1-git-send-email-ego@linux.vnet.ibm.com/

v1: https://lore.kernel.org/linuxppc-dev/1594120299-31389-1-git-send-email-ego@linux.vnet.ibm.com/

The change from v2 --> v1 :

 * Patch 1: Got rid of some #define-s which were needed mainly for Patches4 and
   5 of v1, but were retained in v2.

 * Patch 2:

  	* Based on feedback from Michael Ellerman, rewrote the
	  function to parse the extended idle states by explicitly
	  defining the structure of the object that is returned by
	  ibm,get-system-parameters(CEDE_LATENCY_TOKEN) rtas-call. In
	  the previous versions we were passing a character array and
	  subsequently parsing the individual elements which can be
	  bug-prone. This also gets rid of the excessive (cast *)ing
	  that was in the previous versions.

	  * Marked some of the functions static and annotated some of
	  the functions with __init and data with __initdata. This
	  makes Sparse happy.

	  * Added comments for CEDE_LATENCY_TOKEN.

	  * Renamed add_pseries_idle_states() to
            parse_xcede_idle_states(). Again, this is because Patch 4
            and 5 from v1 are no longer there.

 * Patch 3: No functional changes, but minor changes to be consistent
   with Patch 1 and 2 of this series.

I have additionally tested the code on POWER8 dedicated LPAR and found
that it has no impact, since the wakeup latency of CEDE(1) is 30us
which is greater that default latency that we are assuming for
CEDE(0). So we do not need to fixup CEDE(0) latency on POWER8.

Vaidy, I have removed your Reviewed-by for v1, since the code has
changed a little bit.

Gautham R. Shenoy (3):
  cpuidle-pseries: Set the latency-hint before entering CEDE
  cpuidle-pseries: Add function to parse extended CEDE records
  cpuidle-pseries : Fixup exit latency for CEDE(0)

 drivers/cpuidle/cpuidle-pseries.c | 190 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 188 insertions(+), 2 deletions(-)

-- 
1.9.4