From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938090AbdEYNXs (ORCPT ); Thu, 25 May 2017 09:23:48 -0400 Received: from foss.arm.com ([217.140.101.70]:50080 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933110AbdEYNXr (ORCPT ); Thu, 25 May 2017 09:23:47 -0400 Cc: Sudeep Holla , Linux Kernel Mailing List , Devicetree List , Alexey Klimov , Jassi Brar , Rob Herring Subject: Re: [PATCH v2 2/6] Documentation: devicetree: add bindings to support ARM MHU doorbells To: Jassi Brar References: <1495621003-4291-1-git-send-email-sudeep.holla@arm.com> <1495621003-4291-3-git-send-email-sudeep.holla@arm.com> From: Sudeep Holla Organization: ARM Message-ID: Date: Thu, 25 May 2017 14:23:44 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 25/05/17 14:22, Jassi Brar wrote: > On Wed, May 24, 2017 at 3:46 PM, Sudeep Holla wrote: >> The ARM MHU has mechanism to assert interrupt signals to facilitate >> inter-processor message based communication. It drives the signal using >> a 32-bit register, with all 32-bits logically ORed together. It also >> enables software to set, clear and check the status of each of the bits >> of this register independently. Each bit of the register can be >> associated with a type of event that can contribute to raising the >> interrupt thereby allowing it to be used as independent doorbells. >> >> Since the first version of this binding can't support doorbells, >> this patch extends the existing binding to support them. >> >> Cc: Alexey Klimov >> Cc: Jassi Brar >> Cc: Rob Herring >> Cc: devicetree@vger.kernel.org >> Signed-off-by: Sudeep Holla >> --- >> .../devicetree/bindings/mailbox/arm-mhu.txt | 46 ++++++++++++++++++++-- >> 1 file changed, 43 insertions(+), 3 deletions(-) >> >> diff --git a/Documentation/devicetree/bindings/mailbox/arm-mhu.txt b/Documentation/devicetree/bindings/mailbox/arm-mhu.txt >> index 4971f03f0b33..bd9a3a267caf 100644 >> --- a/Documentation/devicetree/bindings/mailbox/arm-mhu.txt >> +++ b/Documentation/devicetree/bindings/mailbox/arm-mhu.txt >> @@ -10,21 +10,42 @@ STAT register and the remote clears it after having read the data. >> The last channel is specified to be a 'Secure' resource, hence can't be >> used by Linux running NS. >> >> +The MHU drives the interrupt signal using a 32-bit register, with all >> +32-bits logically ORed together. It provides a set of registers to >> +enable software to set, clear and check the status of each of the bits >> +of this register independently. The use of 32 bits per interrupt line >> +enables software to provide more information about the source of the >> +interrupt. For example, each bit of the register can be associated with >> +a type of event that can contribute to raising the interrupt. Each of >> +the 32-bits can be used as "doorbell" to alert the remote processor. >> + >> Mailbox Device Node: >> ==================== >> >> Required properties: >> -------------------- >> -- compatible: Shall be "arm,mhu" & "arm,primecell" >> +- compatible: Shall be "arm,primecell" and one of the below: >> + "arm,mhu" - if the controller doesn't support >> + doorbell model >> + "arm,mhu-doorbell" - if the controller supports >> + doorbell model >> - reg: Contains the mailbox register address range (base >> address and length) >> -- #mbox-cells Shall be 1 - the index of the channel needed. >> +- #mbox-cells Shall be 1 - the index of the channel needed when >> + compatible is "arm,mhu" >> + Shall be 2 - the index of the channel needed, and >> + the index of the doorbell bit with the channel when >> + compatible is "arm,mhu-doorbell" >> - interrupts: Contains the interrupt information corresponding to >> - each of the 3 links of MHU. >> + each of the 3 physical channels of MHU namely low >> + priority non-secure, high priority non-secure and >> + secure channels. >> >> Example: >> -------- >> >> +1. Controller which doesn't support doorbells >> + >> mhu: mailbox@2b1f0000 { >> #mbox-cells = <1>; >> compatible = "arm,mhu", "arm,primecell"; >> @@ -41,3 +62,22 @@ used by Linux running NS. >> reg = <0 0x2e000000 0x4000>; >> mboxes = <&mhu 1>; /* HP-NonSecure */ >> }; >> + >> +2. Controller which supports doorbells >> + >> + mhu: mailbox@2b1f0000 { >> + #mbox-cells = <2>; >> + compatible = "arm,mhu-doorbell", "arm,primecell"; >> + reg = <0 0x2b1f0000 0x1000>; >> + interrupts = <0 36 4>, /* LP-NonSecure */ >> + <0 35 4>, /* HP-NonSecure */ >> + <0 37 4>; /* Secure */ >> + clocks = <&clock 0 2 1>; >> + clock-names = "apb_pclk"; >> + }; >> + >> + mhu_client: scb@2e000000 { >> + compatible = "arm,scpi"; >> + reg = <0 0x2e000000 0x200>; >> + mboxes = <&mhu 1 4>; /* HP-NonSecure 5th doorbell bit */ >> + }; >> > Every MHU controller can by driven as "arm,mhu-doorbell" or "arm,mhu" > equally fine. So you are basically smuggling a s/w feature into DT. > I disagree, the spec clearly says each bit can be used for different event and hence we need a way to specify that in DT when used as doorbell. -- Regards, Sudeep