linux-kernel - Re: [PATCH 3/3] arm64: boot: dts: ti: k3-am62l3-evm: enable WKUP UART wakeup from LPM

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Message-ID: <20260106115658.susgttqvokqeasz3@width>
Date: Tue, 6 Jan 2026 05:56:58 -0600
From: Nishanth Menon <nm@...com>
To: Kendall Willis <k-willis@...com>
CC: Vignesh Raghavendra <vigneshr@...com>, Tero Kristo <kristo@...nel.org>,
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Dhruva Gole <d-gole@...com>, "Bryan
 Brattlof" <bb@...com>, <vishalm@...com>, <sebin.francis@...com>,
	<msp@...libre.com>, <khilman@...libre.com>, <a-kaur@...com>,
	<s-kochidanadu@...com>, <linux-arm-kernel@...ts.infradead.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] arm64: boot: dts: ti: k3-am62l3-evm: enable WKUP
 UART wakeup from LPM

On 16:10-20260105, Kendall Willis wrote:
> On 1/5/26 07:55, Nishanth Menon wrote:
> > On 20:51-20251230, Kendall Willis wrote:
> > > Change the status of the wkup_uart0_interconnect node to enabled. The
> > > target-module node sets the UART SYSC and SYSS registers to allow wakeup
> > > from WKUP UART in DeepSleep low power mode.
> > > 
> > > Signed-off-by: Kendall Willis <k-willis@...com>
> > > ---
> > >   arch/arm64/boot/dts/ti/k3-am62l3-evm.dts | 4 ++++
> > >   1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/arch/arm64/boot/dts/ti/k3-am62l3-evm.dts b/arch/arm64/boot/dts/ti/k3-am62l3-evm.dts
> > > index cae04cce337366b50928d39b0c888550b14e43d3..02b1a1c76b2ee05d49cd69d199a6aacdb1973fa0 100644
> > > --- a/arch/arm64/boot/dts/ti/k3-am62l3-evm.dts
> > > +++ b/arch/arm64/boot/dts/ti/k3-am62l3-evm.dts
> > > @@ -359,3 +359,7 @@ &usb1 {
> > >   	pinctrl-names = "default";
> > >   	pinctrl-0 = <&usb1_default_pins>;
> > >   };
> > > +
> > > +&wkup_uart0_interconnect {
> > > +	status = "okay";
> > > +};
> > 
> > don't we need to set status okay and provide pinmux for wkup_uart?
> > 
> 
> No, only the interconnect target node needs to be enabled because it manages
> the SYSC register. The SYSC register configures the WKUP_UART to be able to
> wakeup the SoC from system suspend. This allows the WKUP_UART to be wakeup
> capable even if it is reserved by firmware.
> 

If wkup_uart is controlled by firmware, it should be managed by
firmware. $subject claims that wkup_uart is being enabled, but it is
not.


-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D
https://ti.com/opensource