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From: Peter Griffin <peter.griffin@linaro.org>
To: "André Draszik" <andre.draszik@linaro.org>,
	"Tudor Ambarus" <tudor.ambarus@linaro.org>,
	"Rob Herring" <robh@kernel.org>,
	"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Alim Akhtar" <alim.akhtar@samsung.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org,  devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,  kernel-team@android.com,
	willmcvicker@google.com, dan.carpenter@linaro.org,
	 arnd@arndb.de, robh@kernel.org,
	Peter Griffin <peter.griffin@linaro.org>
Subject: [PATCH v2 2/2] arm64: dts: exynos: gs101: remove syscon compatible from pmu node
Date: Fri, 14 Nov 2025 12:00:17 +0000	[thread overview]
Message-ID: <20251114-remove-pmu-syscon-compat-v2-2-9496e8c496c7@linaro.org> (raw)
In-Reply-To: <20251114-remove-pmu-syscon-compat-v2-0-9496e8c496c7@linaro.org>

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 mentioned in that commit, it's not correct to claim we are compatible
with syscon, as a MMIO regmap created by syscon won't work. Removing the
syscon compatible means syscon driver won't ever create a mmio regmap.

Note this isn't usually an issue today as exynos-pmu runs at an early
initcall so the custom regmap will have been registered first. However
changes proposed in [1] will bring -EPROBE_DEFER support to syscon allowing
this mechanism to be more robust, especially in highly modularized systems.

Technically this is a ABI break but no other platforms are
affected. Additionally (with the benefit of hindsight) a MMIO syscon has
never worked for PMU register writes, thus the ABI break is justified.

Link: https://lore.kernel.org/lkml/aQdHmrchkmOr34r3@stanley.mountain/ [1]
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
---
Changes in v2:
 - Update commit message (Krzysztof)
---
 arch/arm64/boot/dts/exynos/google/gs101.dtsi | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/exynos/google/gs101.dtsi b/arch/arm64/boot/dts/exynos/google/gs101.dtsi
index d06d1d05f36408137a8acd98e43d48ea7d4f4292..e1a7d33fd4a369f7b352b81d2070beb62a0ced16 100644
--- a/arch/arm64/boot/dts/exynos/google/gs101.dtsi
+++ b/arch/arm64/boot/dts/exynos/google/gs101.dtsi
@@ -1705,7 +1705,7 @@ sysreg_apm: syscon@17420000 {
 		};
 
 		pmu_system_controller: system-controller@17460000 {
-			compatible = "google,gs101-pmu", "syscon";
+			compatible = "google,gs101-pmu";
 			reg = <0x17460000 0x10000>;
 			google,pmu-intr-gen-syscon = <&pmu_intr_gen>;
 

-- 
2.52.0.rc1.455.g30608eb744-goog


      parent reply	other threads:[~2025-11-14 12:00 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-14 12:00 [PATCH v2 0/2] Remove syscon compatible from google,gs101-pmu node Peter Griffin
2025-11-14 12:00 ` [PATCH v2 1/2] dt-bindings: soc: samsung: exynos-pmu: remove syscon for google,gs101-pmu Peter Griffin
2025-11-20  0:09   ` Rob Herring (Arm)
2025-11-14 12:00 ` Peter Griffin [this message]

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