linux-kernel - [PATCH v3 0/2] MIPS: CPS: Optimise delay CPU calibration and cluster helper function

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Message-Id: <20250708-smp_calib-v3-0-6dabf01a7d9f@bootlin.com>
Date: Tue, 08 Jul 2025 15:46:10 +0200
From: Gregory CLEMENT <gregory.clement@...tlin.com>
To: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: Jiaxun Yang <jiaxun.yang@...goat.com>, 
 Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>, 
 Théo Lebrun <theo.lebrun@...tlin.com>, 
 Tawfik Bayouk <tawfik.bayouk@...ileye.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, linux-mips@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Gregory CLEMENT <gregory.clement@...tlin.com>
Subject: [PATCH v3 0/2] MIPS: CPS: Optimise delay CPU calibration and
 cluster helper function

This series allow booting faster by reusing the delay calibration
across the CPU belonging of the same cluster. While doing it we now
reuse the mips_cps_first_online_in_cluster() that we improve also.

This series enables faster booting by reusing delay calibration across
CPUs within the same cluster. During this process, we reuse the
improved mips_cps_first_online_in_cluster function.

With the introduction of this series, a configuration running 32 cores
spread across two clusters sees a significant reduction in boot time
by approximately 600 milliseconds.

Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
---
Changes in v3:
- Do not depend anymore of a Kconfig entry (suggested by Jiaxun).
- cpumask for cluster filled now later in cps_prepare_cpus().
- Patch 2 of the v2 has been removed.
- Link to v2: https://lore.kernel.org/r/20250704-smp_calib-v2-0-bade7e9c0463@bootlin.com

Changes in v2:
- Add a patch improving mips_cps_first_online_in_cluster()
- Use mips_cps_first_online_in_cluster() in calibrate_delay_is_known()
  as suggested by Jiaxun
- Link to v1: https://lore.kernel.org/r/20250520-smp_calib-v1-1-cd04f0a78648@bootlin.com

---
Gregory CLEMENT (2):
      MIPS: CPS: Improve mips_cps_first_online_in_cluster()
      MIPS: CPS: Optimise delay CPU calibration for SMP

 arch/mips/include/asm/mips-cps.h |  4 +++-
 arch/mips/include/asm/smp-cps.h  |  1 +
 arch/mips/kernel/mips-cm.c       | 47 ++++++++++++++--------------------------
 arch/mips/kernel/smp-cps.c       | 16 +++++++++++++-
 4 files changed, 35 insertions(+), 33 deletions(-)
---
base-commit: 86731a2a651e58953fc949573895f2fa6d456841
change-id: 20250520-smp_calib-6d3009e1f5b9

Best regards,
-- 
Grégory CLEMENT, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com