From mboxrd@z Thu Jan 1 00:00:00 1970 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 86371E7E0BC for ; Mon, 9 Feb 2026 16:46:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=NnLHAoRJZStKVitvldth2QKtbNsm/0SoBCuqkKTDn4A=; b=zNggwmzB/tPpbBpkjBiAaqsBjq 1q520QW4LANyJ4tNTQbjv9CRH8KojgTX/uFL8hbiIlgCWHQoePTLoxklYv8KU1R9ZtMVy7QvdNoya L1miWVMa3Nd4Qc4KywVN+sBM8dgeU/BaA2zn82c/f/hDmISZC3Bwfn5uhcVTqWBjTAqolLiBWEC94 9hvu4uQZToisZKPw4dkdwvNf50OAacVDtE0TSnSbeObV4+CLSfdganYV2Yb3E5IT51e5rU9fcWE7m wtC1AX+iCIms1Pr1um+uzkc0/7a6EDxA6d23Y4kj/s2BXywgEpBswKsZvKi37AdGUfp6gB/d3zKYG ayIi/glA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vpUOS-0000000FiEg-3T4y; Mon, 09 Feb 2026 16:45:48 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vpUOO-0000000FiE2-3I39 for linux-arm-kernel@lists.infradead.org; Mon, 09 Feb 2026 16:45:47 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A92C2339; Mon, 9 Feb 2026 08:45:33 -0800 (PST) Received: from pluto (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 542823F63F; Mon, 9 Feb 2026 08:45:38 -0800 (PST) Date: Mon, 9 Feb 2026 16:45:35 +0000 From: Cristian Marussi To: Douglas Anderson Cc: jassisinghbrar@gmail.com, arm-scmi@vger.kernel.org, cristian.marussi@arm.com, krzk@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, sudeep.holla@kernel.org Subject: Re: [PATCH v2 03/15] firmware: arm_scmi: Use mbox_ring_doorbell() instead of NULL message Message-ID: References: <20260208040240.1971442-1-dianders@chromium.org> <20260207200128.v2.3.I4a01e1fa771c0b1ea7e35882784e4b7f8f33f65b@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260207200128.v2.3.I4a01e1fa771c0b1ea7e35882784e4b7f8f33f65b@changeid> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260209_084545_327236_06C887BD X-CRM114-Status: GOOD ( 17.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sat, Feb 07, 2026 at 08:01:25PM -0800, Douglas Anderson wrote: > As per the patch ("mailbox: Deprecate NULL mbox messages; Introduce > mbox_ring_doorbell()"), we want to switch all users of NULL mailbox > messages to use mbox_ring_doorbell(). Hi, > > The mbox_ring_doorbell() explicitly documents not to call > mbox_client_txdone() for doorbells, so remove the call. > > NOTE: this mailbox client appears to send doorbells and regular > messages on the same mailbox channel (smbox->chan), so it needs some > extra attention. Specifically, the new API behaves differently if you > ring a doorbell while a non-doorbell message is in progress. I don't > believe that this is something we have to worry about with this > mailbox client, though, because the code was calling > mbox_client_txdone() after sending the NULL message. Had a non-mailbox > message been in progress, that would have marked the in-progress > message as done instead of marking the NULL message as done. > Yes indeed in the SCMI stack on Linux we use both regular non-doorbell messaging for cmd/reply exchanges and 'pure' doorbell messaging, where these latter usually are meant to to signal completion and they are issued on a distinct channel where NO non-doorbell message is sent ever: IOW doorbell and non-doorbell do NOT get mixed up in the same channel...so it should safe... ...having said that, just in case, I tested this series on a JUNO board using ARM MHU (bidirectional) mailboxes and I have NOT seen any anomaly. Tested-by: Cristian Marussi Anyway...Sudeep, who was already in CC, has a couple of mailbox/pcc related series in flight on the list, so he may want to chime in on those. Btw, Thanks for this cleanup ! Now the intent is certainly more explicit and less ambiguous than using a dummy NULL message to trigger a doorbell. Thanks, Cristian