Re: [PATCH 2/2] arm64: dts: mediatek: cherry: Add CPU supply dependency to cpufreq-hw
From: AngeloGioacchino Del Regno
Date: Tue Jan 02 2024 - 04:09:41 EST
Il 02/01/24 07:11, Viresh Kumar ha scritto:
On 29-12-23, 18:28, Nícolas F. R. A. Prado wrote:
When the mediatek-cpufreq-hw driver enables the hardware (by
writing to REG_FREQ_ENABLE), if the regulator supplying the voltage to
the big CPUs hasn't probed yet, the platform hangs shortly after and
"rcu: INFO: rcu_preempt detected stalls on CPUs/tasks" are printed in
the log.
To prevent this from happening, describe the big CPUs regulator in the
performance-controller DT node, so that devlink ensures the regulator
has been probed and configured before the frequency scaling hardware is
probed and enabled.
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@xxxxxxxxxxxxx>
---
arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi b/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
index dd5b89b73190..505da60eee90 100644
--- a/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
+++ b/arch/arm64/boot/dts/mediatek/mt8195-cherry.dtsi
@@ -502,6 +502,10 @@ &pcie1 {
pinctrl-0 = <&pcie1_pins_default>;
};
+&performance {
+ big-cpus-supply = <&mt6315_6_vbuck1>;
+};
+
&pio {
mediatek,rsel-resistance-in-si-unit;
pinctrl-names = "default";
I think the regulator needs to be mentioned in the CPU's node and not
here ?
Even if the regulator voltage is being changed by firmware with cpufreq-hw, the
actual regulators should go to each CPU node and not in the cpufreq driver node,
I agree with Viresh.
Besides, that's the same thing that we're doing with mediatek-cpufreq as well...
and since we're talking about that, we should also do something about this such
that we stop declaring `regulator-always-on` for CPU cores in devicetree, but
this is probably slightly out of context for what you're trying to do here, so,
read that as an "extra consideration" :-)
Cheers,
Angelo