linux-kernel - [PATCH v2 0/2] Remove syscon compatible from google,gs101-pmu node

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Message-Id: <20251114-remove-pmu-syscon-compat-v2-0-9496e8c496c7@linaro.org>
Date: Fri, 14 Nov 2025 12:00:15 +0000
From: Peter Griffin <peter.griffin@...aro.org>
To: André Draszik <andre.draszik@...aro.org>, 
 Tudor Ambarus <tudor.ambarus@...aro.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Alim Akhtar <alim.akhtar@...sung.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 kernel-team@...roid.com, willmcvicker@...gle.com, dan.carpenter@...aro.org, 
 arnd@...db.de, robh@...nel.org, Peter Griffin <peter.griffin@...aro.org>
Subject: [PATCH v2 0/2] Remove syscon compatible from google,gs101-pmu node

Hi folks,

This series removes the syscon compatible from the pmu_system_controller
node, by updating both yaml bindings and device tree.

Since commit ba5095ebbc7a ("mfd: syscon: Allow syscon nodes without a
"syscon" compatible") it is possible to register a regmap without the
syscon compatible in the node.

As noted in that commit, it isn't really correct to claim we are compatible
with syscon, as a MMIO regmap created by syscon driver won't work on gs101.
Removing the syscon compatible means the syscon driver won't ever attempt
to create a mmio regmap.

Currently we rely on exynos-pmu running and registering its regmap at a
very early initcall level, so no mmio created regmap is returned. For
pinctrl driver that runs at the same initcall level as exynos-pmu today we
have a custom exynos_get_pmu_regmap_by_phandle() API that supports
-EPROBE_DEFER.

However with the changes proposed in [1] -EPROBE_DEFER will become
supported in the syscon driver directly making this whole approach more
robust especially in a highly modularized system with other drivers at the
same initcall level. We should also be able to remove the custom API
referenced above.

Technically this is a ABI break but no other platforms are affected. With
an old DT we will have the behaviour of today (rely on early initcall
levels). But once [1] is merged, with a new DT we will benefit from
-EPROBE_DEFER. Additionally PMU write register access was never working
with a mmio syscon so the ABI break is justified.

regards,

Peter

Link: https://lore.kernel.org/lkml/aQdHmrchkmOr34r3@stanley.mountain/ [1]

Signed-off-by: Peter Griffin <peter.griffin@...aro.org>
---
Changes in v2:
- Update commit description (Krzysztof)
- Change Items to enum, remove const (Krzysztof)
- Checkpatch warning commit msg length (Krzysztof)
- Link to v1: https://lore.kernel.org/r/20251103-remove-pmu-syscon-compat-v1-0-f2cb7f9ade6f@linaro.org

---
Peter Griffin (2):
      dt-bindings: soc: samsung: exynos-pmu: remove syscon for google,gs101-pmu
      arm64: dts: exynos: gs101: remove syscon compatible from pmu node

 Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml | 3 ++-
 arch/arm64/boot/dts/exynos/google/gs101.dtsi                  | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)
---
base-commit: 72fb0170ef1f45addf726319c52a0562b6913707
change-id: 20251102-remove-pmu-syscon-compat-dbbc492a4eea

Best regards,
-- 
Peter Griffin <peter.griffin@...aro.org>