linux-kernel - [PATCH v2] ARM: dts: rockchip: rk3xx: disable arm_global

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Date:   Sun, 30 Oct 2022 21:56:29 +0100
From:   Johan Jonker <jbx6244@...il.com>
To:     heiko@...ech.de
Cc:     robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Subject: [PATCH v2] ARM: dts: rockchip: rk3xx: disable arm_global_timer

The clock source and the sched_clock provided by the arm_global_timer
on Rockchip rk3066a/rk3188 are quite unstable because their rates
depend on the CPU frequency.

Recent changes to the arm_global_timer driver makes it impossible to use.

On the other side, the arm_global_timer has a higher rating than the
ROCKCHIP_TIMER, it will be selected by default by the time framework
while we want to use the stable Rockchip clock source.

Keep the arm_global_timer disabled in order to have the
DW_APB_TIMER (rk3066a) or ROCKCHIP_TIMER (rk3188) selected by default.

Signed-off-by: Johan Jonker <jbx6244@...il.com>
---

ARM: dts: rockchip: disable arm-global-timer for rk3188
https://lore.kernel.org/linux-rockchip/1492374441-23336-26-git-send-email-daniel.lezcano@linaro.org/

clocksource: arm_global_timer: implement rate compensation whenever source clock changes
https://lore.kernel.org/all/20210406130045.15491-2-andrea.merello@gmail.com/
---
 arch/arm/boot/dts/rk3188.dtsi | 1 -
 arch/arm/boot/dts/rk3xxx.dtsi | 7 +++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/rk3188.dtsi b/arch/arm/boot/dts/rk3188.dtsi
index cdd4a0bd5..486a96ce2 100644
--- a/arch/arm/boot/dts/rk3188.dtsi
+++ b/arch/arm/boot/dts/rk3188.dtsi
@@ -607,7 +607,6 @@

 &global_timer {
 	interrupts = <GIC_PPI 11 (GIC_CPU_MASK_SIMPLE(4) | IRQ_TYPE_EDGE_RISING)>;
-	status = "disabled";
 };

 &local_timer {
diff --git a/arch/arm/boot/dts/rk3xxx.dtsi b/arch/arm/boot/dts/rk3xxx.dtsi
index bf285091a..b0ec459ff 100644
--- a/arch/arm/boot/dts/rk3xxx.dtsi
+++ b/arch/arm/boot/dts/rk3xxx.dtsi
@@ -76,6 +76,13 @@
 		reg = <0x1013c200 0x20>;
 		interrupts = <GIC_PPI 11 (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_EDGE_RISING)>;
 		clocks = <&cru CORE_PERI>;
+		status = "disabled";
+		/* The clock source and the sched_clock provided by the arm_global_timer
+		 * on Rockchip rk3066a/rk3188 are quite unstable because their rates
+		 * depend on the CPU frequency.
+		 * Keep the arm_global_timer disabled in order to have the
+		 * DW_APB_TIMER (rk3066a) or ROCKCHIP_TIMER (rk3188) selected by default.
+		 */
 	};

 	local_timer: local-timer@...3c600 {
--
2.20.1