linux-kernel - [PATCH v3 2/4] dt-bindings: memory: tegra20: emc: Document new LPDDR2 sub-node

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Date:   Sun,  3 Oct 2021 04:32:33 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: [PATCH v3 2/4] dt-bindings: memory: tegra20: emc: Document new LPDDR2 sub-node

Some Tegra20 boards don't have RAM code stored in NVMEM, which is used for
the memory chip identification and the identity information should be read
out from LPDDR2 chip in this case. Document new sub-node containing generic
LPDDR2 properties that will be used for the memory chip identification if
RAM code isn't available. The identification is done by reading out memory
configuration values from generic LPDDR2 mode registers of SDRAM chip and
comparing them with the values of device-tree sub-node's.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 .../memory-controllers/nvidia,tegra20-emc.yaml  | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/Documentation/devicetree/bindings/memory-controllers/nvidia,tegra20-emc.yaml b/Documentation/devicetree/bindings/memory-controllers/nvidia,tegra20-emc.yaml
index cac6842dc8f1..65f7c3898ac4 100644
--- a/Documentation/devicetree/bindings/memory-controllers/nvidia,tegra20-emc.yaml
+++ b/Documentation/devicetree/bindings/memory-controllers/nvidia,tegra20-emc.yaml
@@ -164,13 +164,14 @@ patternProperties:
       "#size-cells":
         const: 0
 
+      lpddr2-configuration:
+        $ref: "jedec,lpddr2.yaml#"
+        type: object
+
     patternProperties:
       "^emc-table@[0-9]+$":
         $ref: "#/$defs/emc-table"
 
-    required:
-      - nvidia,ram-code
-
     additionalProperties: false
 
 required:
@@ -186,6 +187,8 @@ additionalProperties: false
 
 examples:
   - |
+    #include <dt-bindings/memory/lpddr2.h>
+
     external-memory-controller@...0f400 {
         compatible = "nvidia,tegra20-emc";
         reg = <0x7000f400 0x400>;
@@ -226,5 +229,13 @@ examples:
                         0x007fe010 0x00001414 0x00000000 0x00000000
                         0x00000000 0x00000000 0x00000000 0x00000000>;
             };
+
+            lpddr2-configuration {
+                jedec,lpddr2-manufacturer-id = <LPDDR2_MANID_ELPIDA>;
+                jedec,lpddr2-revision-id1 = <1>;
+                jedec,lpddr2-density-mbits = <2048>;
+                jedec,lpddr2-io-width-bits = <16>;
+                jedec,lpddr2-type = <LPDDR2_TYPE_S4>;
+            };
         };
     };
-- 
2.32.0