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Thu, 15 Jan 2026 11:09:36 -0600 Received: from [128.247.81.19] (uda0506412.dhcp.ti.com [128.247.81.19]) by lelvem-mr05.itg.ti.com (8.18.1/8.18.1) with ESMTP id 60FH9a5j1892836; Thu, 15 Jan 2026 11:09:36 -0600 Message-ID: <9ea936b0-4426-46b1-9935-2a849e7621c1@ti.com> Date: Thu, 15 Jan 2026 11:09:36 -0600 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/3] arm64: boot: dts: ti: k3-am62l: allow WKUP UART wakeup from LPM To: Nishanth Menon CC: Bryan Brattlof , Vignesh Raghavendra , "Tero Kristo" , Rob Herring , "Krzysztof Kozlowski" , Conor Dooley , "Dhruva Gole" , , , , , , , , , References: <20260106-wkup-uart-wakeup-v2-0-fb4cbd56c827@ti.com> <20260107164504.ehvbfizg7ybbvv2e@bryanbrattlof.com> <20260108170545.cfez6dvwkft2z3jh@bryanbrattlof.com> <20260108180341.t2q6msdh5plbrjf4@parabola> Content-Language: en-US From: Kendall Willis In-Reply-To: <20260108180341.t2q6msdh5plbrjf4@parabola> Content-Type: text/plain; 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X-OriginatorOrg: ti.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Jan 2026 17:09:44.6525 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fc6c6aa8-0ac5-4dbe-c142-08de5458e158 X-MS-Exchange-CrossTenant-Id: e5b49634-450b-4709-8abb-1e2b19b982b7 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=e5b49634-450b-4709-8abb-1e2b19b982b7;Ip=[198.47.21.194];Helo=[flwvzet200.ext.ti.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF00004FBA.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR10MB6060 On 1/8/26 12:03, Nishanth Menon wrote: > On 11:52-20260108, Kendall Willis wrote: >> On 1/8/26 11:05, Bryan Brattlof wrote: >>> On January 7, 2026 thus sayeth Kendall Willis: >>>> On 1/7/26 10:45, Bryan Brattlof wrote: >>>>> 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? >>>> >>>> On AM62L, the WKUP UART pinmux is initially set by TFA so that it is set to >>>> the UART pins, not GPIO. The target-module node sets the WKUP UART SYSC >>>> register so that wakeup is enabled. >>>> >>> >>> Nice however should we mark the UART in the board file as reserved for >>> TFA or is it free to be used by Linux and only during the low power >>> modes after Linux is asleep will it be used by TFA? >>> >>> ~Bryan >> >> Sorry for the confusion, I said earlier that the WKUP UART could be used by >> firmware, but that is not to say it is specifically reserved by the firmware >> in general. TFA sets the WKUP UART pins, but it does not use the WKUP UART >> for anything else. The only exception for TFA using the WKUP UART is if the >> user chooses to use the WKUP UART for TFA debugging [1]. >> >> All of this to say that the WKUP UART *can* be used by Linux, it does not >> need to be reserved for firmware. >> > > If you are going to use it for linux wakeup, then why dont we enable it for > linux? what TFA does or not should not dictate device tree unless it is > a hardware description - provide the full description in dt. > When adding a full description of WKUP UART and setting the WKUP UART to be enabled in Linux, the wakeup functionality stopped working. I am currently debugging this since I don't think that it should matter if the WKUP UART is enabled or disabled for the wakeup functionality to work with this implementation. I will post another version of this series once I am able to fix the problem. Best, Kendall Willis