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bh=p+Jyx/3SNbd8LRAUKMO+bqq+INYj8uTh6OWad9ZPL3k=; b=Hus3msysfDoo /aM2EWOJkJULKWGqSvbNlwOmzR7Uy5Ke28dF00TRkypiyCGHzKdZ/msgYvIehf6tMZlzmzCn8QinM Ila+JWKZIprpOeB40tBy86/fK+lWqWaM+VsonwqEEAZ5oJL7KHk7tPuMs+gxeHpb3IpHrzx0Gr+n0 vCbSYHtoy+YSRioWsm71Rys2ZdAvXMsACR0RPaYiSwzDSqSThcpiq2eU77xjv8/rZso6IacDXcjxk f8UdZMZ1m4t2SLGkAJ8E2Je8fIocIzz6C2f7kKARy05eEQ0K9ftM9+FHzB9W++RXE1l1Vg/olVenZ Bs89wDvUKrVupVmgaQBnZQ==; Received: from 108-223-40-66.lightspeed.sntcca.sbcglobal.net ([108.223.40.66]:47996) by bh-25.webhostbox.net with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.100.1) (envelope-from ) id 1xSG6v-00000004MEQ-12rL; Sat, 14 Nov 2026 21:26:13 +0530 Message-ID: Date: Sat, 14 Nov 2026 07:56:12 -0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] watchdog: Add ARM TWD (MPCore private) watchdog driver To: filipp.dunsky@gmail.com, Wim Van Sebroeck Cc: linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org, Russell King , linux-arm-kernel@lists.infradead.org References: <20261114-arm-twd-wdt-v4-1-5a3104b36331@gmail.com> Content-Language: en-US From: Guenter Roeck Autocrypt: addr=linux@roeck-us.net; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-BWhitelist: no X-Source-IP: 108.223.40.66 X-Source-L: No X-Exim-ID: 1xSG6v-00000004MEQ-12rL X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 108-223-40-66.lightspeed.sntcca.sbcglobal.net [108.223.40.66]:47996 X-Source-Auth: guenter@roeck-us.net X-Email-Count: 4 X-Org: HG=direseller_whb_net_legacy;ORG=directi; X-Source-Cap: cm9lY2s7YWN0aXZzdG07YmgtMjUud2ViaG9zdGJveC5uZXQ= X-Local-Domain: yes X-CMAE-Envelope: MS4xfLTfB5uxJXqeysv79DoyL0RkHfsv1Q9A4fMQ19M3Vczl4fEFJ2X2aReAq3zP0+fNFJOyX3XKH0RDqhHIiRDuFccEJetwyZPC7YOQrJ73Ycm0fHJVdV8K fSfAKxW+3HfjPOGOM0Gad+UYrM7y4FET6meiSgybm/r08fMHWmjFwLdx0lY9IqNH1LTUXuhwHKb5xCDtVkLkUyJJkdUB/3pvi+sOF9dR8m5KQINVVkLqQoqU On 11/14/26 06:11, Fil Dunsky via B4 Relay wrote: > From: Fil Dunsky > > ARM11 MPCore, Cortex-A5 and Cortex-A9 MPCore systems have a watchdog > next to the local timer of every CPU, banked at the same address. The > binding "arm,cortex-a9-twd-wdt" exists, but there has been no driver > since mpcore_wdt was removed in v3.11, among other reasons because it > only ever programmed the CPU that ran the ioctl. > > Program, ping and stop the watchdogs of all online CPUs together with > on_each_cpu(), and use a CPU hotplug state to arm the watchdog of a CPU > coming online while the device is active and to stop it on a CPU going > offline, which could not ping it any more. The watchdog is used in reset > mode only, its interrupt is not needed. > Watchdog drivers are supposed to watch the system as a whole, not on a per-CPU level. This patch goes way beyond the scope of a system watchdog driver. Per-CPU watchdogs are handled in kernel/watchdog.c. I do not think it is a good idea to overlay that with a second per-CPU watchdog mechanism. Guenter