From patchwork Tue Jul 19 19:53:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Guilherme G. Piccoli" X-Patchwork-Id: 12922953 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3131C43334 for ; Tue, 19 Jul 2022 19:55:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237910AbiGSTzt (ORCPT ); Tue, 19 Jul 2022 15:55:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42978 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237521AbiGSTzs (ORCPT ); Tue, 19 Jul 2022 15:55:48 -0400 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9B40454AF1; Tue, 19 Jul 2022 12:55:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=hvFngS+SbTqGKT0e1yD1Flbk7O+3mk0+bQWnmDbivHg=; b=M7NtTBbllawpOvTPCtUXyQYrO3 ALhnZaAkIF7GELFRa+HHmcpunYKDBRXEarjjsjqgbaYk5qxIvZxn4RJ7595HAkdjHbv359ZL37BFb NhwIsMNhkqm59nWgarDJPIl5SoZA3vvxo1F3NQE6HTjudo4mf1NcQCpWFFopt5+kOCctQs1gGkSzo vhH9WYJF1N/oQeLYAOL/w1rEbKcuPSgkuZgtTqMrTNVaBQjMMKrvARQ1M2RvZLOIC6rIO5dDF7KiS C3EL0HOtOX6zk5OWjhAfny3yrw7xSrb4hmzoOKuurM/2LLYaD037g0y0hXZ3Fok5yhYKfJ2MZdsIn sbn4nutw==; Received: from 200-100-212-117.dial-up.telesp.net.br ([200.100.212.117] helo=localhost) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1oDtJi-006fNi-SW; Tue, 19 Jul 2022 21:55:39 +0200 From: "Guilherme G. Piccoli" To: akpm@linux-foundation.org, bhe@redhat.com, pmladek@suse.com, kexec@lists.infradead.org Cc: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, netdev@vger.kernel.org, x86@kernel.org, kernel-dev@igalia.com, kernel@gpiccoli.net, halves@canonical.com, fabiomirmar@gmail.com, alejandro.j.jimenez@oracle.com, andriy.shevchenko@linux.intel.com, arnd@arndb.de, bp@alien8.de, corbet@lwn.net, d.hatayama@jp.fujitsu.com, dave.hansen@linux.intel.com, dyoung@redhat.com, feng.tang@intel.com, gregkh@linuxfoundation.org, mikelley@microsoft.com, hidehiro.kawai.ez@hitachi.com, jgross@suse.com, john.ogness@linutronix.de, keescook@chromium.org, luto@kernel.org, mhiramat@kernel.org, mingo@redhat.com, paulmck@kernel.org, peterz@infradead.org, rostedt@goodmis.org, senozhatsky@chromium.org, stern@rowland.harvard.edu, tglx@linutronix.de, vgoyal@redhat.com, vkuznets@redhat.com, will@kernel.org, "Guilherme G. Piccoli" , bcm-kernel-feedback-list@broadcom.com, Brian Norris , Doug Berger , Justin Chen , Lee Jones , Markus Mayer , Florian Fainelli Subject: [PATCH v2 04/13] soc: bcm: brcmstb: Document panic notifier action and remove useless header Date: Tue, 19 Jul 2022 16:53:17 -0300 Message-Id: <20220719195325.402745-5-gpiccoli@igalia.com> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220719195325.402745-1-gpiccoli@igalia.com> References: <20220719195325.402745-1-gpiccoli@igalia.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The panic notifier of this driver is very simple code-wise, just a memory write to a special position with some numeric code. But this is not clear from the semantic point-of-view, and there is no public documentation about that either. After discussing this in the mailing-lists [0] and having Florian explained it very well, document that in the code for the future generations asking the same questions. Also, while at it, remove a useless header. [0] https://lore.kernel.org/lkml/781cafb0-8d06-8b56-907a-5175c2da196a@gmail.com Cc: Brian Norris Cc: Doug Berger Cc: Justin Chen Cc: Lee Jones Cc: Markus Mayer Acked-by: Florian Fainelli Signed-off-by: Guilherme G. Piccoli --- V2: - Removed the Fixes tag; - Added Florian's ACK - thanks! drivers/soc/bcm/brcmstb/pm/pm-arm.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/soc/bcm/brcmstb/pm/pm-arm.c b/drivers/soc/bcm/brcmstb/pm/pm-arm.c index 70ad0f3dce28..2a6adaa29596 100644 --- a/drivers/soc/bcm/brcmstb/pm/pm-arm.c +++ b/drivers/soc/bcm/brcmstb/pm/pm-arm.c @@ -25,7 +25,6 @@ #include #include #include -#include #include #include #include @@ -664,7 +663,20 @@ static void __iomem *brcmstb_ioremap_match(const struct of_device_id *matches, return of_io_request_and_map(dn, index, dn->full_name); } - +/* + * The AON is a small domain in the SoC that can retain its state across + * various system wide sleep states and specific reset conditions; the + * AON DATA RAM is a small RAM of a few words (< 1KB) which can store + * persistent information across such events. + * + * The purpose of the below panic notifier is to help with notifying + * the bootloader that a panic occurred and so that it should try its + * best to preserve the DRAM contents holding that buffer for recovery + * by the kernel as opposed to wiping out DRAM clean again. + * + * Reference: comment from Florian Fainelli, at + * https://lore.kernel.org/lkml/781cafb0-8d06-8b56-907a-5175c2da196a@gmail.com + */ static int brcmstb_pm_panic_notify(struct notifier_block *nb, unsigned long action, void *data) {