From patchwork Sat Jul 1 23:10:01 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Conor Dooley X-Patchwork-Id: 13299132 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4140BC001B0 for ; Sat, 1 Jul 2023 23:10:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=sEuL2ZIGztD6fUwx+YImKwT6PHvVSh19P4IzCQt0CQg=; b=CMvvinj4QHDjCc wfi0pv3ZkApeqmeR+yEV8IwJ4zgdL/+nQ9smRXPiOvakXszhGm4afC1tbe6otWAaozVIK1K1tzP9q G6EVMAPNjDjBNBNdbGSd6Xnonz2cannQ9P7yVpYi63Mczjbr4aB5+L7makCd5VSdqvJoaefQ/Ej1z wseF/jAWIiK4ZlkzNAkHZ4SUEwQPxMXFej4bsq8utlWoWnI4fklhmoyMU06AFZY+8SNOpbSo87O5s V5KJtH7iUJyMzsFbZhca/6P3ZpxHN4FIBcJbTYwE8AW4L2Zu5fNVxBKYweRQuZYnn6BPihP1vMFlP mpfz3oUYNF21tvSSd7KA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qFjjg-006mQT-1l; Sat, 01 Jul 2023 23:10:36 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qFjja-006mPj-2M for linux-riscv@lists.infradead.org; Sat, 01 Jul 2023 23:10:35 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C5320602E8; Sat, 1 Jul 2023 23:10:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 496F7C433C8; Sat, 1 Jul 2023 23:10:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688253029; bh=/cbcnzOILAY+PGM41uwdmjk8lzxF2uual9TtRTYYAT4=; h=From:To:Cc:Subject:Date:From; b=LA6vtTB28FqiXpqRAy1uCmfjKNBrvAvsD91TCJD1BxGbxhTpWzVTQ1MrdYaQJkFI0 c2l7VSRRQO2H3tClGpvLdFGncVWcS9FgPrftrpkLq0BfrtHdVXcrhQh7zcPb/ItfBo oCY7PkJUOiYhcd7NKvZvIy/yps6PVkVEG6idv6FGEMhaoPPyp0amvvBmvOOxaneUYT vdU/qQLSfCOQID3x8RYCRZ+TDsPTFVpt3Sb5gV6GbogbOCk634Qd/l47fR7ToiOQNV dFoOeaVWKaEhL4lFmrUh58bKo7rJ8cUYq/x37DEpMaYz+uO4hJRqhSTHKc+jbTUW1f H1w26/noEENgQ== From: Conor Dooley To: palmer@dabbelt.com Cc: conor@kernel.org, Conor Dooley , Paul Walmsley , Rob Herring , Krzysztof Kozlowski , Alistair Francis , Andrew Jones , Anup Patel , Atish Patra , Jessica Clarke , Rick Chen , Leo , Oleksii , linux-riscv@lists.infradead.org, qemu-riscv@nongnu.org, u-boot@lists.denx.de, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Palmer Dabbelt , Rob Herring Subject: [PATCH v5] dt-bindings: riscv: deprecate riscv,isa Date: Sun, 2 Jul 2023 00:10:01 +0100 Message-Id: <20230702-eats-scorebook-c951f170d29f@spud> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=21375; i=conor.dooley@microchip.com; h=from:subject:message-id; bh=VNPgTFHgpj7uYTYZQczY5FQxuzxbDkOynyswRASSlsc=; b=owGbwMvMwCFWscWwfUFT0iXG02pJDCkLNrmp+07YH6S0/LTBvCvXjlvZ5Tmy817btb6nbYPtD 0PWKgbBjlIWBjEOBlkxRZbE230tUuv/uOxw7nkLM4eVCWQIAxenAExEIZSRoVt1tXhFS3Sj945Z PT+DPijEzV20aoPMEscL9wueXHNNFGb4X8g5ffO95S4NYYLdHZ3Bq19na39ynPFSbkfEo7+v37Y J8QAA X-Developer-Key: i=conor.dooley@microchip.com; a=openpgp; fpr=F9ECA03CF54F12CD01F1655722E2C55B37CF380C X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230701_161032_557286_53A050F2 X-CRM114-Status: GOOD ( 37.04 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Conor Dooley intro ===== When the RISC-V dt-bindings were accepted upstream in Linux, the base ISA etc had yet to be ratified. By the ratification of the base ISA, incompatible changes had snuck into the specifications - for example the Zicsr and Zifencei extensions were spun out of the base ISA. Fast forward to today, and the reason for this patch. Currently the riscv,isa dt property permits only a specific subset of the ISA string - in particular it excludes version numbering. With the current constraints, it is not possible to discern whether "rv64i" means that the hart supports the fence.i instruction, for example. Future systems may choose to implement their own instruction fencing, perhaps using a vendor extension, or they may not implement the optional counter extensions. Software needs a way to determine this. versioning schemes ================== "Use the extension versions that are described in the ISA manual" you may say, and it's not like this has not been considered. Firstly, software that parses the riscv,isa property at runtime will need to contain a lookup table of some sort that maps arbitrary versions to versions it understands. There is not a consistent application of version number applied to extensions, with a higgledy-piggledy collection of tags, "bare" and versioned documents awaiting the reader on the "recently ratified extensions" page: https://wiki.riscv.org/display/HOME/Recently+Ratified+Extensions As an aside, and this is reflected in the patch too, since many extensions have yet to appear in a release of the ISA specs, they are defined by commits in their respective "working draft" repositories. Secondly, there is an issue of backwards compatibility, whereby allowing numbers in the ISA string, some parsers may be broken. This would require an additional property to be created to even use the versions in this manner. ~boolean properties~ string array property ========================================== If a new property is needed, the whole approach may as well be looked at from the bottom up. A string with limited character choices etc is hardly the best approach for communicating extension information to software. Switching to using properties that are defined on a per extension basis, allows us to define explicit meanings for the DT representation of each extension - rather than the current situation where different operating systems or other bits of software may impart different meanings to characters in the string. Clearly the best source of meanings is the specifications themselves, this just provides us the ability to choose at what point in time the meaning is set. If an extension changes incompatibility in the future, a new property will be required. Off-list, some of the RVI folks have committed to shoring up the wording in either the ISA specifications, the riscv-isa-manual or so that in the future, modifications to and additions or removals of features will require a new extension. Codifying that assertion somewhere would make it quite unlikely that compatibility would be broken, but we have the tools required to deal with it, if & when it crops up. It is in our collective interest, as consumers of extension meanings, to define a scheme that enforces compatibility. The use of individual elements, rather than a single string, will also permit validation that the properties have a meaning, as well as potentially reject mutually exclusive combinations, or enforce dependencies between extensions. That would not have be possible with the current dt-schema infrastructure for arbitrary strings, as we would need to add a riscv,isa parser to dt-validate! That's not implemented in this patch, but rather left as future work (for the brave, or the foolish). parser simplicity ================= Many systems that parse DT at runtime already implement an function that can check for the presence of a string in an array of string, as it is similar to the process for parsing a list of compatible strings, so a bunch of new, custom, DT parsing should not be needed. Getting rid of "riscv,isa" parsing would be a nice simplification, but unfortunately for backwards compatibility with old dtbs, existing parsers may not be removable - which may greatly simplify dt parsing code. In Linux, for example, checking for whether a hart supports an extension becomes as simple as: of_property_match_string(node, "riscv,isa-extensions", "zicbom") vendor extensions ================= Compared to riscv,isa, this proposed scheme promotes vendor extensions, oft touted as the strength of RISC-V, to first-class citizens. At present, extensions are defined as meaning what the RISC-V ISA specifications say they do. There is no realistic way of using that interface to provide cross-platform definitions for what vendor extensions mean. Vendor extensions may also have even less consistency than RVI do in terms of versioning, or no care about backwards compatibility. The new property allows us to assign explicit meanings on a per vendor extension basis, backed up by a description of their meanings. fin === Create a new file to store the extension meanings and a new riscv,isa-base property to replace the aspect of riscv,isa that is not represented by the new property - the base ISA implemented by a hart. As a starting point, add properties for extensions currently used in Linux. Finally, mark riscv,isa as deprecated, as removing support for it in existing programs would be an ABI break. CC: Palmer Dabbelt CC: Paul Walmsley CC: Rob Herring CC: Krzysztof Kozlowski CC: Alistair Francis CC: Andrew Jones CC: Anup Patel CC: Atish Patra CC: Jessica Clarke CC: Rick Chen CC: Leo CC: Oleksii CC: linux-riscv@lists.infradead.org CC: qemu-riscv@nongnu.org CC: u-boot@lists.denx.de CC: devicetree@vger.kernel.org CC: linux-kernel@vger.kernel.org Reviewed-by: Palmer Dabbelt Acked-by: Palmer Dabbelt Reviewed-by: Rob Herring Signed-off-by: Conor Dooley --- Changes in v5: - s/oneOf/anyOf/ so that having both new and old properties passes dt-validate. Changes in v4: - Drop the ACPI section at Anup's request. - Pick up tags from Rob. - Reword some counter access clarification bits in I & Zicsr. Changes in v3: - Per Rob's suggestion, switch to an array of strings. Cuts down on the size, compared to booleans. It has a standard mechanism for parsing (you need to parse arrays of strings for compatibles). It still allows for having a limited set of explicitly defined properties - so the advantages over a free-form string still apply. - Pick up Palmer's Ack and Review (although I expect that he will be the one to apply this). --- .../devicetree/bindings/riscv/cpus.yaml | 43 ++- .../devicetree/bindings/riscv/extensions.yaml | 250 ++++++++++++++++++ 2 files changed, 270 insertions(+), 23 deletions(-) create mode 100644 Documentation/devicetree/bindings/riscv/extensions.yaml diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml index 67bd239ead0b..38c0b5213736 100644 --- a/Documentation/devicetree/bindings/riscv/cpus.yaml +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml @@ -25,6 +25,7 @@ description: | allOf: - $ref: /schemas/cpu.yaml# + - $ref: extensions.yaml properties: compatible: @@ -82,25 +83,6 @@ properties: description: The blocksize in bytes for the Zicboz cache operations. - riscv,isa: - description: - Identifies the specific RISC-V instruction set architecture - supported by the hart. These are documented in the RISC-V - User-Level ISA document, available from - https://riscv.org/specifications/ - - Due to revisions of the ISA specification, some deviations - have arisen over time. - Notably, riscv,isa was defined prior to the creation of the - Zicntr, Zicsr, Zifencei and Zihpm extensions and thus "i" - implies "zicntr_zicsr_zifencei_zihpm". - - While the isa strings in ISA specification are case - insensitive, letters in the riscv,isa string must be all - lowercase. - $ref: /schemas/types.yaml#/definitions/string - pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:[hsxz](?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$ - # RISC-V has multiple properties for cache op block sizes as the sizes # differ between individual CBO extensions cache-op-block-size: false @@ -139,8 +121,17 @@ properties: DMIPS/MHz, relative to highest capacity-dmips-mhz in the system. +anyOf: + - required: + - riscv,isa + - required: + - riscv,isa-base + +dependencies: + riscv,isa-base: [ "riscv,isa-extensions" ] + riscv,isa-extensions: [ "riscv,isa-base" ] + required: - - riscv,isa - interrupt-controller unevaluatedProperties: false @@ -160,7 +151,9 @@ examples: i-cache-sets = <128>; i-cache-size = <16384>; reg = <0>; - riscv,isa = "rv64imac"; + riscv,isa-base = "rv64i"; + riscv,isa-extensions = "i", "m", "a", "c"; + cpu_intc0: interrupt-controller { #interrupt-cells = <1>; compatible = "riscv,cpu-intc"; @@ -183,8 +176,10 @@ examples: i-tlb-size = <32>; mmu-type = "riscv,sv39"; reg = <1>; - riscv,isa = "rv64imafdc"; tlb-split; + riscv,isa-base = "rv64i"; + riscv,isa-extensions = "i", "m", "a", "f", "d", "c"; + cpu_intc1: interrupt-controller { #interrupt-cells = <1>; compatible = "riscv,cpu-intc"; @@ -202,8 +197,10 @@ examples: device_type = "cpu"; reg = <0>; compatible = "riscv"; - riscv,isa = "rv64imafdc"; mmu-type = "riscv,sv48"; + riscv,isa-base = "rv64i"; + riscv,isa-extensions = "i", "m", "a", "f", "d", "c"; + interrupt-controller { #interrupt-cells = <1>; interrupt-controller; diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml new file mode 100644 index 000000000000..cc1f546fdbdc --- /dev/null +++ b/Documentation/devicetree/bindings/riscv/extensions.yaml @@ -0,0 +1,250 @@ +# SPDX-License-Identifier: (GPL-2.0 OR MIT) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/riscv/extensions.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: RISC-V ISA extensions + +maintainers: + - Paul Walmsley + - Palmer Dabbelt + - Conor Dooley + +description: | + RISC-V has a large number of extensions, some of which are "standard" + extensions, meaning they are ratified by RISC-V International, and others + are "vendor" extensions. + This document defines properties that indicate whether a hart supports a + given extension. + + Once a standard extension has been ratified, no changes in behaviour can be + made without the creation of a new extension. + The properties for standard extensions therefore map to their originally + ratified states, with the exception of the I, Zicntr & Zihpm extensions. + See the "i" property for more information. + +select: + properties: + compatible: + contains: + const: riscv + +properties: + riscv,isa: + description: + Identifies the specific RISC-V instruction set architecture + supported by the hart. These are documented in the RISC-V + User-Level ISA document, available from + https://riscv.org/specifications/ + + Due to revisions of the ISA specification, some deviations + have arisen over time. + Notably, riscv,isa was defined prior to the creation of the + Zicntr, Zicsr, Zifencei and Zihpm extensions and thus "i" + implies "zicntr_zicsr_zifencei_zihpm". + + While the isa strings in ISA specification are case + insensitive, letters in the riscv,isa string must be all + lowercase. + $ref: /schemas/types.yaml#/definitions/string + pattern: ^rv(?:64|32)imaf?d?q?c?b?k?j?p?v?h?(?:[hsxz](?:[a-z])+)?(?:_[hsxz](?:[a-z])+)*$ + deprecated: true + + riscv,isa-base: + description: + The base ISA implemented by this hart, as described by the 20191213 + version of the unprivileged ISA specification. + enum: + - rv32i + - rv64i + + riscv,isa-extensions: + $ref: /schemas/types.yaml#/definitions/string-array + minItems: 1 + description: Extensions supported by the hart. + items: + anyOf: + # single letter extensions, in canonical order + - const: i + description: | + The base integer instruction set, as ratified in the 20191213 + version of the unprivileged ISA specification. + + This does not include Chapter 10, "Counters", which was moved into + the Zicntr and Zihpm extensions after the ratification of the + 20191213 version of the unprivileged specification. + + - const: m + description: + The standard M extension for integer multiplication and division, as + ratified in the 20191213 version of the unprivileged ISA + specification. + + - const: a + description: + The standard A extension for atomic instructions, as ratified in the + 20191213 version of the unprivileged ISA specification. + + - const: f + description: + The standard F extension for single-precision floating point, as + ratified in the 20191213 version of the unprivileged ISA + specification. + + - const: d + description: + The standard D extension for double-precision floating-point, as + ratified in the 20191213 version of the unprivileged ISA + specification. + + - const: q + description: + The standard Q extension for quad-precision floating-point, as + ratified in the 20191213 version of the unprivileged ISA + specification. + + - const: c + description: + The standard C extension for compressed instructions, as ratified in + the 20191213 version of the unprivileged ISA specification. + + - const: v + description: + The standard V extension for vector operations, as ratified + in-and-around commit 7a6c8ae ("Fix text that describes vfmv.v.f + encoding") of the riscv-v-spec. + + - const: h + description: + The standard H extension for hypervisors as ratified in the 20191213 + version of the privileged ISA specification. + + # multi-letter extensions, sorted alphanumerically + - const: smaia + description: | + The standard Smaia supervisor-level extension for the advanced + interrupt architecture for machine-mode-visible csr and behavioural + changes to interrupts as frozen at commit ccbddab ("Merge pull + request #42 from riscv/jhauser-2023-RC4") of riscv-aia. + + - const: ssaia + description: | + The standard Ssaia supervisor-level extension for the advanced + interrupt architecture for supervisor-mode-visible csr and + behavioural changes to interrupts as frozen at commit ccbddab + ("Merge pull request #42 from riscv/jhauser-2023-RC4") of riscv-aia. + + - const: sscofpmf + description: | + The standard Sscofpmf supervisor-level extension for count overflow + and mode-based filtering as ratified at commit 01d1df0 ("Add ability + to manually trigger workflow. (#2)") of riscv-count-overflow. + + - const: sstc + description: | + The standard Sstc supervisor-level extension for time compare as + ratified at commit 3f9ed34 ("Add ability to manually trigger + workflow. (#2)") of riscv-time-compare. + + - const: svinval + description: + The standard Svinval supervisor-level extension for fine-grained + address-translation cache invalidation as ratified in the 20191213 + version of the privileged ISA specification. + + - const: svnapot + description: + The standard Svnapot supervisor-level extensions for napot + translation contiguity as ratified in the 20191213 version of the + privileged ISA specification. + + - const: svpbmt + description: + The standard Svpbmt supervisor-level extensions for page-based + memory types as ratified in the 20191213 version of the privileged + ISA specification. + + - const: zba + description: | + The standard Zba bit-manipulation extension for address generation + acceleration instructions as ratified at commit 6d33919 ("Merge pull + request #158 from hirooih/clmul-fix-loop-end-condition") of + riscv-bitmanip. + + - const: zbb + description: | + The standard Zbb bit-manipulation extension for basic bit-manipulation + as ratified at commit 6d33919 ("Merge pull request #158 from + hirooih/clmul-fix-loop-end-condition") of riscv-bitmanip. + + - const: zbc + description: | + The standard Zbc bit-manipulation extension for carry-less + multiplication as ratified at commit 6d33919 ("Merge pull request + #158 from hirooih/clmul-fix-loop-end-condition") of riscv-bitmanip. + + - const: zbs + description: | + The standard Zbs bit-manipulation extension for single-bit + instructions as ratified at commit 6d33919 ("Merge pull request #158 + from hirooih/clmul-fix-loop-end-condition") of riscv-bitmanip. + + - const: zicbom + description: + The standard Zicbom extension for base cache management operations as + ratified in commit 3dd606f ("Create cmobase-v1.0.pdf") of riscv-CMOs. + + - const: zicbop + description: + The standard Zicbop extension for cache-block prefetch instructions + as ratified in commit 3dd606f ("Create cmobase-v1.0.pdf") of + riscv-CMOs. + + - const: zicboz + description: + The standard Zicboz extension for cache-block zeroing as ratified + in commit 3dd606f ("Create cmobase-v1.0.pdf") of riscv-CMOs. + + - const: zicntr + description: + The standard Zicntr extension for base counters and timers, as + ratified in the 20191213 version of the unprivileged ISA + specification. + + - const: zicsr + description: | + The standard Zicsr extension for control and status register + instructions, as ratified in the 20191213 version of the + unprivileged ISA specification. + + This does not include Chapter 10, "Counters", which documents + special case read-only CSRs, that were moved into the Zicntr and + Zihpm extensions after the ratification of the 20191213 version of + the unprivileged specification. + + - const: zifencei + description: + The standard Zifencei extension for instruction-fetch fence, as + ratified in the 20191213 version of the unprivileged ISA + specification. + + - const: zihintpause + description: + The standard Zihintpause extension for pause hints, as ratified in + commit d8ab5c7 ("Zihintpause is ratified") of the riscv-isa-manual. + + - const: zihpm + description: + The standard Zihpm extension for hardware performance counters, as + ratified in the 20191213 version of the unprivileged ISA + specification. + + - const: ztso + description: + The standard Ztso extension for total store ordering, as ratified + in commit 2e5236 ("Ztso is now ratified.") of the + riscv-isa-manual. + +additionalProperties: true +...