From mboxrd@z Thu Jan 1 00:00:00 1970 From: "tushar.khandelwal@arm.com" Subject: Re: [PATCH 1/4] mailbox: arm_mhuv2: add device tree binding documentation Date: Wed, 14 Aug 2019 23:20:39 +0100 Message-ID: <685d5c73-42e6-3de4-f607-e8c7f5678bf2@arm.com> References: <20190717192616.1731-1-tushar.khandelwal@arm.com> <20190717192616.1731-2-tushar.khandelwal@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Jassi Brar , Morten Borup Petersen Cc: Linux Kernel Mailing List , "tushar.2nov@gmail.com" , "nd@arm.com" , Morten Borup Petersen , Rob Herring , Mark Rutland , Devicetree List List-Id: devicetree@vger.kernel.org On 13/08/2019 17:36, Jassi Brar wrote: > On Fri, Aug 2, 2019 at 5:41 AM Morten Borup Petersen wrote: >> >> >> >> On 7/31/19 9:31 AM, Jassi Brar wrote: >>> On Sun, Jul 28, 2019 at 4:28 PM Morten Borup Petersen wrote: >>>> >>>> >>>> >>>> On 7/25/19 7:49 AM, Jassi Brar wrote: >>>>> On Sun, Jul 21, 2019 at 4:58 PM Jassi Brar wrote: >>>>>> >>>>>> On Wed, Jul 17, 2019 at 2:26 PM Tushar Khandelwal >>>>>> wrote: >>>>>> >>>>>>> diff --git a/Documentation/devicetree/bindings/mailbox/arm,mhuv2.txt b/Documentation/devicetree/bindings/mailbox/arm,mhuv2.txt >>>>>>> new file mode 100644 >>>>>>> index 000000000000..3a05593414bc >>>>>>> --- /dev/null >>>>>>> +++ b/Documentation/devicetree/bindings/mailbox/arm,mhuv2.txt >>>>>>> @@ -0,0 +1,108 @@ >>>>>>> +Arm MHUv2 Mailbox Driver >>>>>>> +======================== >>>>>>> + >>>>>>> +The Arm Message-Handling-Unit (MHU) Version 2 is a mailbox controller that has >>>>>>> +between 1 and 124 channel windows to provide unidirectional communication with >>>>>>> +remote processor(s). >>>>>>> + >>>>>>> +Given the unidirectional nature of the device, an MHUv2 mailbox may only be >>>>>>> +written to or read from. If a pair of MHU devices is implemented between two >>>>>>> +processing elements to provide bidirectional communication, these must be >>>>>>> +specified as two separate mailboxes. >>>>>>> + >>>>>>> +A device tree node for an Arm MHUv2 device must specify either a receiver frame >>>>>>> +or a sender frame, indicating which end of the unidirectional MHU device which >>>>>>> +the device node entry describes. >>>>>>> + >>>>>>> +An MHU device must be specified with a transport protocol. The transport >>>>>>> +protocol of an MHU device determines the method of data transmission as well as >>>>>>> +the number of provided mailboxes. >>>>>>> +Following are the possible transport protocol types: >>>>>>> +- Single-word: An MHU device implements as many mailboxes as it >>>>>>> + provides channel windows. Data is transmitted through >>>>>>> + the MHU registers. >>>>>>> +- Multi-word: An MHU device implements a single mailbox. All channel windows >>>>>>> + will be used during transmission. Data is transmitted through >>>>>>> + the MHU registers. >>>>>>> +- Doorbell: An MHU device implements as many mailboxes as there are flag >>>>>>> + bits available in its channel windows. Optionally, data may >>>>>>> + be transmitted through a shared memory region, wherein the MHU >>>>>>> + is used strictly as an interrupt generation mechanism. >>>>>>> + >>>>>>> +Mailbox Device Node: >>>>>>> +==================== >>>>>>> + >>>>>>> +Required properties: >>>>>>> +-------------------- >>>>>>> +- compatible: Shall be "arm,mhuv2" & "arm,primecell" >>>>>>> +- reg: Contains the mailbox register address range (base >>>>>>> + address and length) >>>>>>> +- #mbox-cells Shall be 1 - the index of the channel needed. >>>>>>> +- mhu-frame Frame type of the device. >>>>>>> + Shall be either "sender" or "receiver" >>>>>>> +- mhu-protocol Transport protocol of the device. Shall be one of the >>>>>>> + following: "single-word", "multi-word", "doorbell" >>>>>>> + >>>>>>> +Required properties (receiver frame): >>>>>>> +------------------------------------- >>>>>>> +- interrupts: Contains the interrupt information corresponding to the >>>>>>> + combined interrupt of the receiver frame >>>>>>> + >>>>>>> +Example: >>>>>>> +-------- >>>>>>> + >>>>>>> + mbox_mw_tx: mhu@10000000 { >>>>>>> + compatible = "arm,mhuv2","arm,primecell"; >>>>>>> + reg = <0x10000000 0x1000>; >>>>>>> + clocks = <&refclk100mhz>; >>>>>>> + clock-names = "apb_pclk"; >>>>>>> + #mbox-cells = <1>; >>>>>>> + mhu-protocol = "multi-word"; >>>>>>> + mhu-frame = "sender"; >>>>>>> + }; >>>>>>> + >>>>>>> + mbox_sw_tx: mhu@10000000 { >>>>>>> + compatible = "arm,mhuv2","arm,primecell"; >>>>>>> + reg = <0x11000000 0x1000>; >>>>>>> + clocks = <&refclk100mhz>; >>>>>>> + clock-names = "apb_pclk"; >>>>>>> + #mbox-cells = <1>; >>>>>>> + mhu-protocol = "single-word"; >>>>>>> + mhu-frame = "sender"; >>>>>>> + }; >>>>>>> + >>>>>>> + mbox_db_rx: mhu@10000000 { >>>>>>> + compatible = "arm,mhuv2","arm,primecell"; >>>>>>> + reg = <0x12000000 0x1000>; >>>>>>> + clocks = <&refclk100mhz>; >>>>>>> + clock-names = "apb_pclk"; >>>>>>> + #mbox-cells = <1>; >>>>>>> + interrupts = <0 45 4>; >>>>>>> + interrupt-names = "mhu_rx"; >>>>>>> + mhu-protocol = "doorbell"; >>>>>>> + mhu-frame = "receiver"; >>>>>>> + }; >>>>>>> + >>>>>>> + mhu_client: scb@2e000000 { >>>>>>> + compatible = "fujitsu,mb86s70-scb-1.0"; >>>>>>> + reg = <0 0x2e000000 0x4000>; >>>>>>> + mboxes = >>>>>>> + // For multi-word frames, client may only instantiate a single >>>>>>> + // mailbox for a mailbox controller >>>>>>> + <&mbox_mw_tx 0>, >>>>>>> + >>>>>>> + // For single-word frames, client may instantiate as many >>>>>>> + // mailboxes as there are channel windows in the MHU >>>>>>> + <&mbox_sw_tx 0>, >>>>>>> + <&mbox_sw_tx 1>, >>>>>>> + <&mbox_sw_tx 2>, >>>>>>> + <&mbox_sw_tx 3>, >>>>>>> + >>>>>>> + // For doorbell frames, client may instantiate as many mailboxes >>>>>>> + // as there are bits available in the combined number of channel >>>>>>> + // windows ((channel windows * 32) mailboxes) >>>>>>> + , >>>>>>> + , >>>>>>> + ... >>>>>>> + ; >>>>>>> + }; >>>>>> >>>>>> If the mhuv2 instance implements, say, 3 channel windows between >>>>>> sender (linux) and receiver (firmware), and Linux runs two protocols >>>>>> each requiring 1 and 2-word sized messages respectively. The hardware >>>>>> supports that by assigning windows [0] and [1,2] to each protocol. >>>>>> However, I don't think the driver can support that. Or does it? >>>>>> >>>>> Thinking about it, IMO, the mbox-cell should carry a 128 (4x32) bit >>>>> mask specifying the set of windows (corresponding to the bits set in >>>>> the mask) associated with the channel. >>>>> And the controller driver should see any channel as associated with >>>>> variable number of windows 'N', where N is [0,124] >>>>> >>>>> mhu_client1: proto1@2e000000 { >>>>> ..... >>>>> mboxes = <&mbox 0x0 0x0 0x0 0x1> >>>>> } >>>>> >>>>> mhu_client2: proto2@2f000000 { >>>>> ..... >>>>> mboxes = <&mbox 0x0 0x0 0x0 0x6> >>>>> } >>>>> >>>>> Cheers! >>>>> >>>> >>>> As mentioned in the response to your initial comment, the driver does >>>> not currently support mixing protocols. >>>> >>> Thanks for acknowledging that limitation. But lets also address it. >>> >> >> We are hesitant to dedicate time to developing mixing protocols given >> that we don't have any current usecase nor any current platform which >> would support this. >> > Can you please share the client code against which you tested this driver? > From my past experience, I realise it is much more efficient to tidyup > the code myself, than endlessly trying to explain the benefits. > Yes, I will share that soon. > Thanks >