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[2001:8b0:1d0::2]) by smtp.gmail.com with ESMTPSA id a2-20020a05600c224200b003f9b53959a4sm429012wmm.43.2023.06.19.07.29.29 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Jun 2023 07:29:29 -0700 (PDT) From: Peter Maydell To: qemu-devel@nongnu.org Subject: [PULL 29/33] docs: sbsa: document board to firmware interface Date: Mon, 19 Jun 2023 15:29:10 +0100 Message-Id: <20230619142914.963184-30-peter.maydell@linaro.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230619142914.963184-1-peter.maydell@linaro.org> References: <20230619142914.963184-1-peter.maydell@linaro.org> MIME-Version: 1.0 Received-SPF: pass client-ip=2a00:1450:4864:20::32b; envelope-from=peter.maydell@linaro.org; helo=mail-wm1-x32b.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01, WEIRD_QUOTING=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Marcin Juszkiewicz We plan to add more hardware information into DeviceTree to limit amount of hardcoded values in firmware. Signed-off-by: Marcin Juszkiewicz Message-id: 20230531171834.236569-1-marcin.juszkiewicz@linaro.org [PMM: fix format nits, add text about platform version fields from a comment in the C source file] Reviewed-by: Peter Maydell Signed-off-by: Peter Maydell --- docs/system/arm/sbsa.rst | 38 +++++++++++++++++++++++++++++++------- 1 file changed, 31 insertions(+), 7 deletions(-) diff --git a/docs/system/arm/sbsa.rst b/docs/system/arm/sbsa.rst index 016776aed82..f571fe645e7 100644 --- a/docs/system/arm/sbsa.rst +++ b/docs/system/arm/sbsa.rst @@ -6,12 +6,7 @@ any real hardware the ``sbsa-ref`` board intends to look like real hardware. The `Server Base System Architecture `_ defines a minimum base line of hardware support and importantly how the firmware -reports that to any operating system. It is a static system that -reports a very minimal DT to the firmware for non-discoverable -information about components affected by the qemu command line (i.e. -cpus and memory). As a result it must have a firmware specifically -built to expect a certain hardware layout (as you would in a real -machine). +reports that to any operating system. It is intended to be a machine for developing firmware and testing standards compliance with operating systems. @@ -19,7 +14,7 @@ standards compliance with operating systems. Supported devices """"""""""""""""" -The sbsa-ref board supports: +The ``sbsa-ref`` board supports: - A configurable number of AArch64 CPUs - GIC version 3 @@ -30,3 +25,32 @@ The sbsa-ref board supports: - Bochs display adapter on PCIe bus - A generic SBSA watchdog device + +Board to firmware interface +""""""""""""""""""""""""""" + +``sbsa-ref`` is a static system that reports a very minimal devicetree to the +firmware for non-discoverable information about system components. This +includes both internal hardware and parts affected by the qemu command line +(i.e. CPUs and memory). As a result it must have a firmware specifically built +to expect a certain hardware layout (as you would in a real machine). + +DeviceTree information +'''''''''''''''''''''' + +The devicetree provided by the board model to the firmware is not intended +to be a complete compliant DT. It currently reports: + + - CPUs + - memory + - platform version + - GIC addresses + +The platform version is only for informing platform firmware about +what kind of ``sbsa-ref`` board it is running on. It is neither +a QEMU versioned machine type nor a reflection of the level of the +SBSA/SystemReady SR support provided. + +The ``machine-version-major`` value is updated when changes breaking +fw compatibility are introduced. The ``machine-version-minor`` value +is updated when features are added that don't break fw compatibility.