From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D9C3E18DB2A; Thu, 3 Sep 2026 06:39:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788417586; cv=none; b=BSF0RRR/YG5uu5ac86zN8WjsZfftNv5J0s6oMTBhs5q3UukigqU3ep18piXYev1sHUFE22i23WZ9ElS9Jt+2dib5tszHLc0uoRPBcZ7J9+oDoQmOUG8ZpaXuI6gvvAd9hNcTb2exzaLosH0o7cfhS/yxfIIt2KPoLQprjIvu4o8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788417586; c=relaxed/simple; bh=9GpIj4ykMY5ePFG7wgCRhkjr8Tcs0fAGCtsV/XoHgf4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NYRznVue2DxFRnnz2PB4SKe2a2HW9f4MiTM2ANrqGfcL59yD3Ya7RUqyeQGWdPqGjuPC5HvYIhkvwX7lOGwZbGMFGKMzEeOVHuiO9WfiBQS8I8GmAyXbWKCMmwaTprxvIsZBMh5OabUJKgunUjisv38rjJKjweOkn+Q9SHJ0faQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ad8Va8n1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ad8Va8n1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6EE821F00A3A; Thu, 3 Sep 2026 06:39:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788417581; bh=VPF7B3LTWDh/DW091/duRLfEkzauv9zKTVocOUIbt2k=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ad8Va8n198IM2BqiMBl+Tai2HZgE8nxKlvdU1Z5QL4kw+gclDPq8ZlV2dJqBTBwbW 3f2RZTQR8+W0h0x17wktNc+rIeU6r65KreIQp/wzjJVRwHeHaiZgsJTaB9uc6qbCe0 g6fPjGM6//2biDjUHi+s99Fq/QPu1l5WE4fiGXeLWvlcQEAYdhF1Mu1aqBg96oomyM xGoLpaZtZyqLnVO5bbNDIxFK5OzGcqcl1xg69uNwbS7epKB/u3hAywhHlzYpW4fV2O O/odLtTKigUjPLXBmmoqjAJJkOYzkNnCRRwRYKnyHe/LVUfdC/cpK8k0a12PiGz0yI TdgClfCBimyxg== Message-ID: <85401168-1372-4904-b3af-cfcb837947db@kernel.org> Date: Thu, 3 Sep 2026 08:39:33 +0200 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] dt-bindings: power: Add RPMI device power service bindings To: Joshua Yeong Cc: "rahul@summations.net" , "anup@brainfault.org" , "lftan.linux@gmail.com" , "robh@kernel.org" , "krzk+dt@kernel.org" , "conor+dt@kernel.org" , "ulfh@kernel.org" , "pjw@kernel.org" , "palmer@dabbelt.com" , "aou@eecs.berkeley.edu" , "alex@ghiti.fr" , "linux-riscv@lists.infradead.org" , "linux-pm@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20260830152812.312663-1-joshua.yeong@starfivetech.com> <20260830152812.312663-2-joshua.yeong@starfivetech.com> <20260831-fluorescent-garrulous-kraken-74eecd@quoll> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 02/09/2026 13:30, Joshua Yeong wrote: > On Mon, Aug 31, 2026 at 11:38:07AM +0200, Krzysztof Kozlowski wrote: >> On Sun, Aug 30, 2026 at 11:28:11PM +0800, Joshua Yeong wrote: >>> diff --git a/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml b/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml >>> new file mode 100644 >>> index 000000000000..2b7df66ba172 >> >> A nit, subject: drop second/last, redundant "bindings". The >> "dt-bindings" prefix is already stating that these are bindings. >> See also: >> https://elixir.bootlin.com/linux/v7.1-rc7/source/Documentation/devicetree/bindings/submitting-patches.rst#L23 >> > > Ok, I will drop the redundant "bindings" word in v3. > >>> --- /dev/null >>> +++ b/Documentation/devicetree/bindings/power/riscv,rpmi-mpxy-device-power.yaml >>> @@ -0,0 +1,65 @@ >>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) >>> +%YAML 1.2 >>> +--- >>> +$id: http://devicetree.org/schemas/power/riscv,rpmi-mpxy-device-power.yaml# >>> +$schema: http://devicetree.org/meta-schemas/core.yaml# >>> + >>> +title: RISC-V RPMI device power service group based message proxy >>> + >>> +maintainers: >>> + - Joshua Yeong >>> + >>> +description: | >>> + The RISC-V Platform Management Interface (RPMI) [1] defines a >>> + messaging protocol which is modular and extensible. The supervisor >>> + software can send/receive RPMI messages via SBI MPXY extension [2] >>> + or some dedicated supervisor-mode RPMI transport. >>> + >>> + The RPMI specification [1] defines device power service group for >>> + accessing and controlling the power state of platform devices managed >>> + by a platform microcontroller. The SBI implementation (machine mode >>> + firmware or hypervisor) can implement an SBI MPXY channel to allow RPMI >>> + device power service group access to the supervisor software. >>> + >>> + =========================================== >>> + References >>> + =========================================== >>> + >>> + [1] RISC-V Platform Management Interface (RPMI) v1.0 (or higher) >>> + https://github.com/riscv-non-isa/riscv-rpmi/releases >>> + >>> + [2] RISC-V Supervisor Binary Interface (SBI) v3.0 (or higher) >>> + https://github.com/riscv-non-isa/riscv-sbi-doc/releases >>> + >>> +properties: >>> + compatible: >>> + description: >>> + Intended for use by the SBI implementation. >>> + const: riscv,rpmi-mpxy-device-power >>> + >>> + mboxes: >>> + maxItems: 1 >>> + description: >>> + Mailbox channel of the underlying RPMI transport. >>> + >>> + riscv,sbi-mpxy-channel-id: >>> + $ref: /schemas/types.yaml#/definitions/uint32 >> >> Why isn't this just phandle to mbox? Or even implied by mbox channel? As >> your example shows, having same value in two places points that it is >> redundant. >> > > They look alike but they are in different namespaces, so the two values > are not the same number. In this node "mboxes" points at the RPMI shared > memory transport, whose #mbox-cells is 1 and whose cell is an RPMI > service group ID 0x9 for device power. "riscv,sbi-mpxy-channel-id" is > the SBI MPXY channel number that the SBI implementation then creates for But SBI MPXY is also a mailbox, so you are encoding mailbox channel with a different property. > that service group. The node therefore describes a translation > rather than a duplication, consume RPMI service group 0x9 on the > transport and expose it to the supervisor as MPXY channel 0x1002. > > The 0x1002 that does appear twice is spread over two nodes with two > different audiences, sitting under two different mailbox controllers: > > > rpmi-shmem@12c10000 { /* RISC-V machine mode only */ > compatible = "riscv,rpmi-shmem-mbox"; > reg = <...>; > #mbox-cells = <1>; > > power-domain@9 { /* read by the SBI implementation */ > compatible = "riscv,rpmi-mpxy-device-power"; > mboxes = <&rpmi_shmem 0x9>; > riscv,sbi-mpxy-channel-id = <0x1002>; ... so 0x1002 is: > }; > }; > > sbi-mpxy-mbox { /* RISC-V supervisor mode only */ > compatible = "riscv,sbi-mpxy-mbox"; > #mbox-cells = <2>; /* cells: channel_id, MSG_PROT_ID */ > }; > > rpmi-device-power { /* RISC-V supervisor mode only */ > compatible = "riscv,rpmi-device-power"; > mboxes = <&sbi_mpxy_mbox 0x1002 0x0>; exactly this, no? > #power-domain-cells = <1>; > }; > > A phandle from the supervisor node to power-domain@9 would resolve its > "mboxes" to the shared memory transport, which is not something the > supervisor can drive. The windows are owned by machine mode and the > only RPMI mailbox Linux implements is "riscv,sbi-mpxy-mbox". The > supervisor reaches the platform controller through the SBI MPXY extension and > that ABI addresses channels by number, so the channel id has to survive > as a plain integer on both sides of the SBI boundary. > > You can have a look at the diagram in RISC-V ratified specifications in > https://github.com/riscv-non-isa/riscv-rpmi/releases/tag/v1.0 -> riscv-rpmi.pdf > in Figure 2 High Level Architecture. > Best regards, Krzysztof