linux-kernel - Re: [PATCH v2 0/3] arm64: boot: dts: ti: k3-am62l: allow WKUP UART wakeup from LPM

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Message-ID: <20260107164504.ehvbfizg7ybbvv2e@bryanbrattlof.com>
Date: Wed, 7 Jan 2026 10:45:04 -0600
From: Bryan Brattlof <bb@...com>
To: Kendall Willis <k-willis@...com>
CC: Nishanth Menon <nm@...com>, 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>, <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 v2 0/3] arm64: boot: dts: ti: k3-am62l: allow WKUP UART
 wakeup from LPM

On January  6, 2026 thus sayeth Kendall Willis:
> K3 TI AM62L SoC supports wakeup from WKUP UART when the SoC is in the
> DeepSleep low power mode. To allow wakeup from WKUP UART the target-module
> device tree node is enabled. The ti-sysc interconnect target module driver
> is used to configure the the SYSCONFIG related registers. In this case,
> the interconnect target module node configures the WKUP UART to be able to
> wakeup from system suspend. The SYSC register is used to enable wakeup
> from system suspend for the WKUP UART. Refer to 14.7.2.5 UART in the
> AM62L Techincal Reference Manual for registers referenced [1].
> 
> Previous TI SoCs configure the WKUP UART to wakeup from system suspend
> using the ti-sysc interconnect target module driver. Refer to commit
> ce27f7f9e328 ("arm64: dts: ti: k3-am62-wakeup: Configure ti-sysc for
> wkup_uart0") for an example of this.

I think I may be confused. What is setting the pinmux for the wkup_uart 
to allow us to trigger the wake event? It looks like they reset to GPIO 
pins if not set. Is firmware doing this?

~Bryan