linux-kernel - Re: [PATCH v2 1/2] soc: qcom: Add device tree binding for SMEM

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Message-ID: <20150425030242.GA13672@qualcomm.com>
Date:	Fri, 24 Apr 2015 22:02:42 -0500
From:	Andy Gross <agross@...eaurora.org>
To:	Jeffrey Hugo <jhugo@...eaurora.org>
Cc:	Bjorn Andersson <bjorn.andersson@...ymobile.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] soc: qcom: Add device tree binding for SMEM

On Thu, Apr 23, 2015 at 02:01:28PM -0600, Jeffrey Hugo wrote:
> On 4/11/2015 5:32 PM, Bjorn Andersson wrote:
> >Add device tree binding documentation for the Qualcom Shared Memory
> >manager.
> >
> >Signed-off-by: Bjorn Andersson <bjorn.andersson@...ymobile.com>
> >---
> >
> >Changes since v1:
> >- None
> >
> >  .../devicetree/bindings/soc/qcom/qcom,smem.txt     | 49 ++++++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/soc/qcom/qcom,smem.txt
> >
> >diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom,smem.txt b/Documentation/devicetree/bindings/soc/qcom/qcom,smem.txt
> >new file mode 100644
> >index 0000000..d90f839
> >--- /dev/null
> >+++ b/Documentation/devicetree/bindings/soc/qcom/qcom,smem.txt
> >@@ -0,0 +1,49 @@
> >+Qualcomm Shared Memory binding
> >+
> >+This binding describes the Qualcomm Shared Memory, used to share data between
> >+various subsystems and OSes in Qualcomm platforms.
> >+
> >+- compatible:
> >+	Usage: required
> >+	Value type: <stringlist>
> >+	Definition: must be:
> >+		    "qcom,smem"
> >+
> >+- memory-region:
> >+	Usage: required
> >+	Value type: <prop-encoded-array>
> >+	Definition: handle to memory reservation for main smem memory region.
> >+
> >+- reg:
> >+	Usage: optional
> >+	Value type: <prop-encoded-array>
> >+	Definition: base address and size pair for any additional memory areas
> >+		    of the shared memory.
> >+
> >+- hwspinlocks:
> >+	Usage: required
> >+	Value type: <prop-encoded-array>
> >+	Definition: reference to a hwspinlock used to protect allocations from
> >+		    the shared memory
> >+
> >+= EXAMPLE
> >+
> >+	reserved-memory {
> >+		#address-cells = <1>;
> >+		#size-cells = <1>;
> >+		ranges;
> >+
> >+		smem_region: smem@...0000 {
> >+			reg = <0xfa00000 0x200000>;
> >+			no-map;
> >+		};
> >+	};
> >+
> >+	smem@...0000 {
> >+		compatible = "qcom,smem";
> >+
> >+		memory-region = <&smem_region>;
> >+		reg = <0xfc428000 0x4000>;
> >+
> >+		hwlocks = <&tcsr_mutex 3>;
> >+	};
> >
> 
> For my information, is there any intention to support the
> relocatable smem_region by looking it up at init time?  It does not
> seem like it would be possible to support that with this binding.

The APPS processor really doesn't need anything except the memory region in the
DT.  If it was truly going to be dynamic, we could modify the DT in the
bootloader to set the correct address.  We can let the other processors get the
information through the WONCE TCSR registers.

-- 
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

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