From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 460B91E9B3A; Mon, 9 Feb 2026 16:45:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770655541; cv=none; b=OGbwSNg/xBuEfHgrnfEn/iLw3vORcoEaD9a+A07LJIaBRHYDnOLV/FDeeIAelqa2lbHMmleC1y3Js/DlneBqLmhl20qDzLBVIH2V595VOgoIbivEjsIvLDrv6IG7zy0qMQVcSMZ9JFG+XS9AcyvJ35NpMGRHzp0OtT96oUYN61I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770655541; c=relaxed/simple; bh=OVxJhfA9gvOsce5Q5fuDmP9OAvrQRRhDTX+r/Qa5KNw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=llSMAKYnRs2f+u5i/uEq4uqNhX4Ld6tvde6X0yN4eQ7n4Dqowqjg26bZHlIdbo2Nj5/WdT20Pa9412mQrm7RqS7dapw/XwgOwS7dT49Q7FaQ1+OJYIgq2S1Pox5/mirnhWuZTtiHzWdT3xFj6i9Ks5ZWTgSpYVzA/DZTZE+pVjk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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> 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: <20260207200128.v2.3.I4a01e1fa771c0b1ea7e35882784e4b7f8f33f65b@changeid> 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