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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2F9A9C433E0 for ; Wed, 3 Jun 2020 18:28:16 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 0019C2053B for ; Wed, 3 Jun 2020 18:28:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="V8Sqf6Rl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0019C2053B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=4RygKq+7tXmns0NP6H1CB96M2ElXq19jjxcyiYJ4VrQ=; b=V8Sqf6Rlgi4ca9 nvwpzQTW3IhLkGARdpblP2c32uJjWbliyccstzu27Wt/gkYjBMNoKzGfE8+ETr0yV+WcrkO74s9fI rbSxExJAP8A3LpO4xvNId8nxanUEZHtDIDC1gqtMZpfSBNwNUDqoLAgpnk1lwcJbLIkSwjUP74E7J fjiRZ3rRtAHuoBivFUBcgVfJHFjij2xdecGEtvrS2iV+fLXfwmTvHHt8zmizReKtomKtvmK/NszCo GOCpOqEzT+7l64rL9Ae+KYw3Y5qUR6HReF2ARfGVdl1ou0j253sSlqaeGh/eRHojHeamk1/3FeXpv zzgmk04C/2koSC1NSU1w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgY7b-00076L-GC; Wed, 03 Jun 2020 18:28:15 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgY7Y-00075y-0R for linux-arm-kernel@lists.infradead.org; Wed, 03 Jun 2020 18:28:13 +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 B9DF931B; Wed, 3 Jun 2020 11:28:10 -0700 (PDT) Received: from bogus (unknown [10.37.8.135]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9073D3F305; Wed, 3 Jun 2020 11:28:08 -0700 (PDT) Date: Wed, 3 Jun 2020 19:28:05 +0100 From: Sudeep Holla To: Bjorn Andersson Subject: Re: [RFC] dt-bindings: mailbox: add doorbell support to ARM MHU Message-ID: <20200603182805.GD23722@bogus> References: <0a50f0cf5593baeb628dc8606c523665e5e2ae6c.1589519600.git.viresh.kumar@linaro.org> <20200519012927.GT2165@builder.lan> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200519012927.GT2165@builder.lan> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200603_112812_096563_AA24DBCA X-CRM114-Status: GOOD ( 17.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, Arnd Bergmann , Viresh Kumar , Jassi Brar , linux-kernel@vger.kernel.org, Rob Herring , Sudeep Holla , Frank Rowand , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Bjorn, Thanks for the details response. On Mon, May 18, 2020 at 06:29:27PM -0700, Bjorn Andersson wrote: > On Thu 14 May 22:17 PDT 2020, Viresh Kumar wrote: > [...] I find this part nicely summarise your response. > > - With serialization, if we use only one channel as today at every > > priority, if there are 5 requests to send signal to the receiver and > > the dvfs request is the last one in queue (which may be called from > > scheduler's hot path with fast switching), it unnecessarily needs to > > wait for the first four transfers to finish due to the software > > locking imposed by the mailbox framework. This adds additional delay, > > maybe of few ms only, which isn't required by the hardware but just by > > the software and few ms can be important in scheduler's hotpath. > > > > So these 5 requests, are they conveyed by the signals [1,2,3,4,5] or > [BIT(0), BIT(1), BIT(2), BIT(3), BIT(4)]? > Latter in this case. IMO it is platform choice on how to use it. It is equally possible to send 2^31 different signals. But the receiver must also interpret it in the *exact* same way. In this case, the receiver which is platform firmware interprets as individual bit signals. > In the first case you have to serialize things given that e.g. signal 1 > immediately followed by 2 is indistinguishable from 3. > Agree and we are not proposing to break that use case. It exists in the driver/binding today and will continue as is. > If you signals are single-bit notifications then you don't need any > serialization. > Indeed, we are making use of that. -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel