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authorPaul Walmsley <paul.walmsley@sifive.com>2019-05-13 14:51:53 -0700
committerRob Herring <robh@kernel.org>2019-05-22 09:01:00 -0500
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dt-bindings: sifive: describe sifive-blocks versioning
For IP blocks that are generated from the public, open-source sifive-blocks repository, describe the version numbering policy that its maintainers intend to use, upon request from Rob Herring <robh@kernel.org>. Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com> Signed-off-by: Paul Walmsley <paul@pwsan.com> Reviewed-by: Palmer Dabbelt <palmer@sifive.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: Palmer Dabbelt <palmer@sifive.com> Cc: Megan Wachs <megan@sifive.com> Cc: Wesley Terpstra <wesley@sifive.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: devicetree@vger.kernel.org Cc: linux-riscv@lists.infradead.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Rob Herring <robh@kernel.org>
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+DT compatible string versioning for SiFive open-source IP blocks
+
+This document describes the version specification for DT "compatible"
+strings for open-source SiFive IP blocks. HDL for these IP blocks
+can be found in this public repository:
+
+https://github.com/sifive/sifive-blocks
+
+IP block-specific DT compatible strings are contained within the HDL,
+in the form "sifive,<ip-block-name><integer version number>".
+
+An example is "sifive,uart0" from:
+
+https://github.com/sifive/sifive-blocks/blob/v1.0/src/main/scala/devices/uart/UART.scala#L43
+
+Until these IP blocks (or IP integration) support version
+auto-discovery, the maintainers of these IP blocks intend to increment
+the suffixed number in the compatible string whenever the software
+interface to these IP blocks changes, or when the functionality of the
+underlying IP blocks changes in a way that software should be aware of.
+
+Driver developers can use compatible string "match" values such as
+"sifive,uart0" to indicate that their driver is compatible with the
+register interface and functionality associated with the relevant
+upstream sifive-blocks commits. It is expected that most drivers will
+match on these IP block-specific compatible strings.
+
+DT data authors, when writing data for a particular SoC, should
+continue to specify an SoC-specific compatible string value, such as
+"sifive,fu540-c000-uart". This way, if SoC-specific
+integration-specific bug fixes or workarounds are needed, the kernel
+or other system software can match on this string to apply them. The
+IP block-specific compatible string (such as "sifive,uart0") should
+then be specified as a subsequent value.
+
+An example of this style:
+
+ compatible = "sifive,fu540-c000-uart", "sifive,uart0";