linux-kernel - Re: [PATCH v2 4/5] arm64: dts: ti: k3-am62p5-sk: Enable Main UART wakeup

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Message-ID: <20260106115725.qqyg6isf5q7cg52g@renewable>
Date: Tue, 6 Jan 2026 05:57:25 -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>, <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 4/5] arm64: dts: ti: k3-am62p5-sk: Enable Main UART
 wakeup

On 16:06-20260105, Kendall Willis wrote:
> On 1/5/26 07:52, Nishanth Menon wrote:
> > On 20:38-20251230, Kendall Willis wrote:
> > > The Main UART can resume from suspend to RAM states when PIN_WKUP_EN
> > > is enabled. Add the necessary pins needed to wakeup the system. Add the
> > > system idle states that the Main UART can wakeup the system from.
> > 
> > Is the tx and rx pin register states both lost? I wonder why during
> > "wakeup" we set PIN_WKUP_EN ? is'nt that supposed to be set while
> > entering "suspend" state?
> > 
> 
> The UART driver uses the default pinctrl state when the system is active.
> During the process of suspend, the wakeup pinctrl state is selected by the
> UART driver in order to allow wakeup. Upon resume, the default pinctrl state
> is selected again.
> 
> > if the tx pin register state is not lost, then all we need to do is
> > play with the rx pin state (and leave pinctrl-0 as is)?
> > 
> 
> Yes, it can be done where the pinctrl-0 does not change, and there is an
> additional pinctrl pins that has the TX and RX with PIN_WKUP_EN. The logic
> behind both implementations are the same, just a different approach.
> 

Keep the diff to as minimal as needed + update the commit message
please.

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