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Wysocki" Cc: x86@kernel.org, Krzysztof Kozlowski , Conor Dooley , Rob Herring , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Michael Kelley , Saurabh Sengar , Chris Oo , "Kirill A. Shutemov" , linux-hyperv@vger.kernel.org, devicetree@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Ricardo Neri , Yunhong Jiang Subject: Re: [PATCH v5 03/10] dt-bindings: reserved-memory: Wakeup Mailbox for Intel processors Message-ID: <20250630224947.GA3072@ranerica-svr.sc.intel.com> References: <20250627-rneri-wakeup-mailbox-v5-0-df547b1d196e@linux.intel.com> <20250627-rneri-wakeup-mailbox-v5-3-df547b1d196e@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) On Mon, Jun 30, 2025 at 09:02:00PM +0200, Rafael J. Wysocki wrote: > On Sat, Jun 28, 2025 at 5:35 AM Ricardo Neri > wrote: > > > > Add DeviceTree bindings to enumerate the wakeup mailbox used in platform > > firmware for Intel processors. > > > > x86 platforms commonly boot secondary CPUs using an INIT assert, de-assert > > followed by Start-Up IPI messages. The wakeup mailbox can be used when this > > mechanism is unavailable. > > > > The wakeup mailbox offers more control to the operating system to boot > > secondary CPUs than a spin-table. It allows the reuse of same wakeup vector > > for all CPUs while maintaining control over which CPUs to boot and when. > > While it is possible to achieve the same level of control using a spin- > > table, it would require to specify a separate `cpu-release-addr` for each > > secondary CPU. > > > > The operation and structure of the mailbox is described in the > > Multiprocessor Wakeup Structure defined in the ACPI specification. Note > > that this structure does not specify how to publish the mailbox to the > > operating system (ACPI-based platform firmware uses a separate table). No > > ACPI table is needed in DeviceTree-based firmware to enumerate the mailbox. > > > > Add a `compatible` property that the operating system can use to discover > > the mailbox. Nodes wanting to refer to the reserved memory usually define a > > `memory-region` property. /cpus/cpu* nodes would want to refer to the > > mailbox, but they do not have such property defined in the DeviceTree > > specification. Moreover, it would imply that there is a memory region per > > CPU. > > > > Co-developed-by: Yunhong Jiang > > Signed-off-by: Yunhong Jiang > > Signed-off-by: Ricardo Neri > > LGTM from the ACPI specification cross-referencing perspective, so > > Acked-by: Rafael J. Wysocki Thank you Rafael! I hope this looks good to Krzysztof and Rob too.