From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932592AbcHJV5G (ORCPT ); Wed, 10 Aug 2016 17:57:06 -0400 Received: from mail-oi0-f65.google.com ([209.85.218.65]:36332 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932380AbcHJV5E (ORCPT ); Wed, 10 Aug 2016 17:57:04 -0400 Date: Wed, 10 Aug 2016 16:57:02 -0500 From: Rob Herring To: Andre Przywara Cc: Maxime Ripard , Chen-Yu Tsai , linux-sunxi@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jassi Brar , Mark Rutland , devicetree@vger.kernel.org Subject: Re: [RFC PATCH 2/5] DT: mailbox: add binding doc for the ARM SMC mailbox Message-ID: <20160810215702.GA16450@rob-hp-laptop> References: <20160809115303.17032-1-andre.przywara@arm.com> <20160809115303.17032-3-andre.przywara@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160809115303.17032-3-andre.przywara@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 09, 2016 at 12:53:00PM +0100, Andre Przywara wrote: > Signed-off-by: Andre Przywara > --- > .../devicetree/bindings/mailbox/arm-smc.txt | 53 ++++++++++++++++++++++ > 1 file changed, 53 insertions(+) > create mode 100644 Documentation/devicetree/bindings/mailbox/arm-smc.txt > > diff --git a/Documentation/devicetree/bindings/mailbox/arm-smc.txt b/Documentation/devicetree/bindings/mailbox/arm-smc.txt > new file mode 100644 > index 0000000..9919a12 > --- /dev/null > +++ b/Documentation/devicetree/bindings/mailbox/arm-smc.txt > @@ -0,0 +1,53 @@ > +ARM SMC Mailbox Driver > +====================== > + > +This mailbox driver uses the ARM smc (secure monitor call) instruction to > +trigger a mailbox-connected activity in firmware running on the very same > +core as the caller. By nature this operation is synchronous and this > +driver provides no way for asynchronous messages to be delivered the other > +way round, from firmware to the OS. However the value of r0/w0 the firmware > +returns after the smc call is delivered as a received message to the > +mailbox framework, so a synchronous communication can be established. Clever > + > +One usecase of this mailbox is the SCP interface, which uses shared memory > +to transfer commands and parameters and mailboxes to trigger a function > +call. This driver allows SoC without a separate management processor (or > +when such a processor is not available or used) to use this standardized > +interface anyway. > + > +The driver requires no special hardware, any core which supports the SMC > +instruction can be used. This requires firmware in monitor mode/EL3 to > +handle the mailbox message. > + > +Mailbox Device Node: > +==================== > + > +Required properties: > +-------------------- > +- compatible: Shall be "arm,smc-mbox" > +- #mbox-cells Shall be 1 - the index of the channel needed. > +- identifiers An array of 32-bit values specifying the function Minimally, needs 'arm' prefix. 'identifiers' is pretty vague. Perhaps 'arm,smc-func-ids' to say exactly what they are. > + IDs used by each mailbox channel. Those function IDs > + follow the ARM SMC calling convention standard [1]. > + There is one identifier per channel and the number > + of supported channels is determined by the length > + of this array. > + > +Example: > +-------- > + > + mailbox: smc_mbox { > + #mbox-cells = <1>; > + compatible = "arm,smc-mbox"; > + identifiers = <0x82000001 0x82000002>; > + }; > + > + scpi { > + compatible = "arm,scpi"; > + mboxes = <&mailbox 0>; > + shmem = <&cpu_scp_shmem>; > + }; > + > + > +[1] > +http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0028a/index.html > -- > 2.9.0 >