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Fri, 04 Sep 2020 06:00:04 -0700 (PDT) From: Thierry Reding To: Joerg Roedel Subject: [PATCH v2 1/4] dt-bindings: reserved-memory: Document "active" property Date: Fri, 4 Sep 2020 14:59:57 +0200 Message-Id: <20200904130000.691933-1-thierry.reding@gmail.com> X-Mailer: git-send-email 2.28.0 MIME-Version: 1.0 Cc: devicetree@vger.kernel.org, Frank Rowand , Robin Murphy , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Rob Herring , Will Deacon X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" From: Thierry Reding Reserved memory regions can be marked as "active" if hardware is expected to access the regions during boot and before the operating system can take control. One example where this is useful is for the operating system to infer whether the region needs to be identity- mapped through an IOMMU. Signed-off-by: Thierry Reding --- .../bindings/reserved-memory/reserved-memory.txt | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt index 4dd20de6977f..163d2927e4fc 100644 --- a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt +++ b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt @@ -63,6 +63,13 @@ reusable (optional) - empty property able to reclaim it back. Typically that means that the operating system can use that region to store volatile or cached data that can be otherwise regenerated or migrated elsewhere. +active (optional) - empty property + - If this property is set for a reserved memory region, it indicates + that some piece of hardware may be actively accessing this region. + Should the operating system want to enable IOMMU protection for a + device, all active memory regions must have been identity-mapped + in order to ensure that non-quiescent hardware during boot can + continue to access the memory. Linux implementation note: - If a "linux,cma-default" property is present, then Linux will use the -- 2.28.0 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu