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Mon, 15 Jul 2019 10:03:16 -0700 (PDT) X-Gm-Message-State: APjAAAWki1X5I4um7vN6/CCvJF5BYgwvlhvT5jp79VjDrDwdw7uw6lro gZEKiLd+uQrTRgZFnIo8Qu4l9pwVxyYGL4cg8g== X-Google-Smtp-Source: APXvYqx+8VKAvY/IfBFD75fj05NSLbDRiObogw7qXgNRqLXLSq7ia56/S4oerXDR960+R3wf7Kt+ezsVEvT6as7BL0E= X-Received: by 2002:a37:a010:: with SMTP id j16mr18090764qke.152.1563210195522; Mon, 15 Jul 2019 10:03:15 -0700 (PDT) MIME-Version: 1.0 References: <1563184103-8493-1-git-send-email-peng.fan@nxp.com> <1563184103-8493-2-git-send-email-peng.fan@nxp.com> In-Reply-To: <1563184103-8493-2-git-send-email-peng.fan@nxp.com> From: Rob Herring Date: Mon, 15 Jul 2019 11:03:03 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 1/2] dt-bindings: mailbox: add binding doc for the ARM SMC/HVC mailbox To: Peng Fan X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190715_100319_236877_820E1807 X-CRM114-Status: GOOD ( 28.89 ) 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: "mark.rutland@arm.com" , "devicetree@vger.kernel.org" , "f.fainelli@gmail.com" , "andre.przywara@arm.com" , "jassisinghbrar@gmail.com" , "linux-kernel@vger.kernel.org" , dl-linux-imx , "sudeep.holla@arm.com" , "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 On Mon, Jul 15, 2019 at 4:10 AM Peng Fan wrote: > > From: Peng Fan > > The ARM SMC/HVC mailbox binding describes a firmware interface to trigger > actions in software layers running in the EL2 or EL3 exception levels. > The term "ARM" here relates to the SMC instruction as part of the ARM > instruction set, not as a standard endorsed by ARM Ltd. > > Signed-off-by: Peng Fan > --- > > V3: > Convert to yaml > Drop interrupt > Introudce transports to indicate mem/reg > The func id is still kept as optional, because like SCMI it only > cares about message. > > V2: > Introduce interrupts as a property. > > .../devicetree/bindings/mailbox/arm-smc.yaml | 124 +++++++++++++++++++++ > 1 file changed, 124 insertions(+) > create mode 100644 Documentation/devicetree/bindings/mailbox/arm-smc.yaml > > diff --git a/Documentation/devicetree/bindings/mailbox/arm-smc.yaml b/Documentation/devicetree/bindings/mailbox/arm-smc.yaml > new file mode 100644 > index 000000000000..da9b1a03bc4e > --- /dev/null > +++ b/Documentation/devicetree/bindings/mailbox/arm-smc.yaml > @@ -0,0 +1,124 @@ > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) > +%YAML 1.2 > +--- > +$id: http://devicetree.org/schemas/mailbox/arm-smc.yaml# > +$schema: http://devicetree.org/meta-schemas/core.yaml# > + > +title: ARM SMC Mailbox Interface > + > +maintainers: > + - Peng Fan > + > +description: | > + This mailbox uses the ARM smc (secure monitor call) and hvc (hypervisor > + call) instruction to trigger a mailbox-connected activity in firmware, > + executing on the very same core as the caller. By nature this operation > + is synchronous and this mailbox provides no way for asynchronous messages > + to be delivered the other way round, from firmware to the OS, but > + asynchronous notification could also be supported. However the value of > + r0/w0/x0 the firmware returns after the smc call is delivered as a received > + message to the mailbox framework, so a synchronous communication can be > + established, for a asynchronous notification, no value will be returned. > + The exact meaning of both the action the mailbox triggers as well as the > + return value is defined by their users and is not subject to this binding. > + > + One use case of this mailbox is the SCMI interface, which uses shared memory > + to transfer commands and parameters, and a mailbox to trigger a function > + call. This allows SoCs without a separate management processor (or when > + such a processor is not available or used) to use this standardized > + interface anyway. > + > + This binding describes no hardware, but establishes a firmware interface. > + Upon receiving an SMC using one of the described SMC function identifiers, > + the firmware is expected to trigger some mailbox connected functionality. > + The communication follows the ARM SMC calling convention. > + Firmware expects an SMC function identifier in r0 or w0. The supported > + identifiers are passed from consumers, or listed in the the arm,func-ids > + properties as described below. The firmware can return one value in > + the first SMC result register, it is expected to be an error value, > + which shall be propagated to the mailbox client. > + > + Any core which supports the SMC or HVC instruction can be used, as long as > + a firmware component running in EL3 or EL2 is handling these calls. > + > +properties: > + compatible: > + const: arm,smc-mbox > + > + "#mbox-cells": > + const: 1 > + > + arm,num-chans: > + description: The number of channels supported. > + $ref: /schemas/types.yaml#/definitions/uint32 Constraints? 0 is valid? 2^32? > + > + method: > + items: > + - enum: > + - smc > + - hvc > + > + transports: > + items: > + - enum: > + - mem > + - reg What if someone wants to configure this per channel? Perhaps #mbox-cells should be 2 and this can be a client parameter. Minimally, this needs a 'arm' vendor prefix if it stays. > + > + arm,func-ids: > + description: | > + An array of 32-bit values specifying the function IDs used by each > + mailbox channel. Those function IDs follow the ARM SMC calling > + convention standard [1]. What's the default if not specified? Or this should be required? > + > + There is one identifier per channel and the number of supported > + channels is determined by the length of this array. > + minItems: 0 > + maxItems: 4096 # Should be enough? > + > +required: > + - compatible > + - "#mbox-cells" > + - arm,num-chans > + - transports > + - method > + > +examples: > + - | > + sram@910000 { > + compatible = "mmio-sram"; > + reg = <0x0 0x93f000 0x0 0x1000>; > + #address-cells = <1>; > + #size-cells = <1>; > + ranges = <0 0x0 0x93f000 0x1000>; > + > + cpu_scp_lpri: scp-shmem@0 { > + compatible = "arm,scmi-shmem"; > + reg = <0x0 0x200>; > + }; > + > + cpu_scp_hpri: scp-shmem@200 { > + compatible = "arm,scmi-shmem"; > + reg = <0x200 0x200>; > + }; > + }; > + > + firmware { > + smc_mbox: mailbox { > + #mbox-cells = <1>; > + compatible = "arm,smc-mbox"; > + method = "smc"; > + arm,num-chans = <0x2>; > + transports = "mem"; > + /* Optional */ > + arm,func-ids = <0xc20000fe>, <0xc20000ff>; > + }; > + > + scmi { > + compatible = "arm,scmi"; > + mboxes = <&mailbox 0 &mailbox 1>; > + mbox-names = "tx", "rx"; > + shmem = <&cpu_scp_lpri &cpu_scp_hpri>; > + }; > + }; > + > +... > -- > 2.16.4 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel