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Fri, 28 Aug 2026 16:23:16 +0800 (CST) Date: Fri, 28 Aug 2026 16:23:05 +0800 From: Johnny Fan To: Ard Biesheuvel Cc: linux-rtc@vger.kernel.org, Feng Tang , linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, cix-kernel-upstream , Bob Zhang , Jie Fu Subject: Re: [PATCH] rtc: efi: restore alarm support with runtime capability probe Message-ID: References: <20260828031519.2749354-1-johnny.fan@cixtech.com> <549999fa-4b1a-4f53-872a-9036a377f8cf@app.fastmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <549999fa-4b1a-4f53-872a-9036a377f8cf@app.fastmail.com> X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: TY2PEPF0000AB87:EE_|TYQPR06MB8009:EE_ X-MS-Office365-Filtering-Correlation-Id: 31915680-0af5-4f35-3bed-08df04dd9d17 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|36860700016|82310400026|1800799024|23010399003|10067099003|4143699003|6133799003|56012099006|22082099003|18002099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: fh8GxBCT460lb2U1a48I5X3QiXee/F92s4rYTI0NeBcl8680ynQU80eK0NgJDbeBimWI5R8cr5eJSKWcjme75QXrKUYFOrWw7l66Ph8yM3naBxSxs8d3u0eEhioBkMRtD9Q+2wzKCc1ymY5aN92wjfCIb++ugiRZ5yuW2SB8kys2SNt1bCFWBteDzm0txiuCekQXOGuSMT21oHiA7PwcYihT3214LMZ+tQVPA0VE9/wos+w00qiqdblPLOVXISI7nG1riNmvwAUXYFHq9Kc0oFprbSTiOi8k5bKkZsmtmvls6Qi7F3kTO3w2c94uYRxKXApvshX+rbaeQ6ibGX7vE8D4c6wkZPjgriquYmIO5L2t41flAVeHw1/eTn9aCsMODszHt/v1BQbUWdqsOVDPzdSVdpBtz9DIGoreDI99Mao7GCJo1sCopvCYYeL3bem4 X-OriginatorOrg: cixtech.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Aug 2026 08:23:17.7155 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 31915680-0af5-4f35-3bed-08df04dd9d17 X-MS-Exchange-CrossTenant-Id: 0409f77a-e53d-4d23-943e-ccade7cb4811 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=0409f77a-e53d-4d23-943e-ccade7cb4811;Ip=[222.71.101.198];Helo=[smtprelay.cixcomputing.com] X-MS-Exchange-CrossTenant-AuthSource: TY2PEPF0000AB87.apcprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: TYQPR06MB8009 On Fri, Aug 28, 2026 at 09:26:42AM +0200, Ard Biesheuvel wrote: > Why does it need working alarm/wakeup support? > > I'm not saying we shouldn't bring it back, but this deserves a bit of > motivation, no? Hi Ard, Thanks for the review. The reason is wakeup: on CIX platforms, the RTC is an I2C device owned by firmware, and in the ACPI boot configuration the bus is not exposed to the OS, so the EFI runtime services are the only way Linux can program the RTC alarm at all. With it removed, 'rtcwake' fails for both suspend-to-RAM and power-off wakeup -- Linux simply has no other path to set an alarm on this platform. It is also a cross-OS consistency thing: Windows programs the same alarm through the same runtime services, so a shared interface that is time-only on the Linux side is asymmetric. I'll extend the commit message with this motivation in v2. Thanks, Johnny