04.10.2021 10:42, Krzysztof Kozlowski пишет:

On 03/10/2021 03:32, Dmitry Osipenko wrote:

quoted

Add binding for standard LPDDR2 memory chip properties.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 .../memory-controllers/jedec,lpddr2.yaml      | 80 +++++++++++++++++++
 include/dt-bindings/memory/lpddr2.h           | 25 ++++++

Hi Dmitry,

Thanks for doing this. I think I should be slightly more descriptive in
my previous comment. What I meant, is to use existing DDR bindings
(which might include or require converting them to YAML):
Documentation/devicetree/bindings/ddr/

The bindings are already used:
arch/arm/boot/dts/elpida_ecb240abacn.dtsi
arch/arm/boot/dts/exynos5422-odroid-core.dtsi
drivers/memory/samsung/exynos5422-dmc.c

Thanks! I missed that there is ddr/ subdir.

You can remove the Documentation/devicetree/bindings/ddr/lpddr2.txt
after full conversion, so also including AC timings and AC timing
parameters. The timing parameters could be a separate YAML, if you want
to convert everything. You can also skip it, because it is not necessary
for your work.


Rob,
Any advice from your side where to put LPDDR2 dtschema bindings? The
existing location was bindings/ddr/ but maybe this should be part of
memory-controllers (although it is not actually a controller but rather
used by the controller)?

+1 for having it inside of memory-controllers/

quoted

 2 files changed, 105 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/memory-controllers/jedec,lpddr2.yaml
 create mode 100644 include/dt-bindings/memory/lpddr2.h

diff --git a/Documentation/devicetree/bindings/memory-controllers/jedec,lpddr2.yaml b/Documentation/devicetree/bindings/memory-controllers/jedec,lpddr2.yaml
new file mode 100644
index 000000000000..ef227eba1e4a
--- /dev/null
+++ b/Documentation/devicetree/bindings/memory-controllers/jedec,lpddr2.yaml

@@ -0,0 +1,80 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/memory-controllers/jedec,lpddr2.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: JEDEC LPDDR2 SDRAM
+
+maintainers:
+  - Krzysztof Kozlowski <krzk@kernel.org>
+
+properties:

You need compatible (see lpddr2.txt)

quoted

+  jedec,lpddr2-manufacturer-id:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maximum: 255
+    description: |
+      Unique manufacturer ID of SDRAM chip. See MR5 description in JESD209-2.

Plus:
"See include/dt-bindings/memory/lpddr2.h for known manufactured IDs."

However I wonder whether we need it. It should be taken from the vendor
part of compatible.

It shouldn't be needed if compatible is used.

quoted

+
+  jedec,lpddr2-revision-id1:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maximum: 255
+    description: |
+      Revision 1 value of SDRAM chip.
+      See MR6 description in chip vendor specification.
+
+  jedec,lpddr2-revision-id2:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    maximum: 255
+    description: |
+      Revision 2 value of SDRAM chip.
+      See MR7 description in chip vendor specification.
+
+  jedec,lpddr2-density-mbits:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+      Density in megabits of SDRAM chip. See MR8 description in JESD209-2.
+    enum:
+      - 64
+      - 128
+      - 256
+      - 512
+      - 1024
+      - 2048
+      - 4096
+      - 8192
+      - 16384
+      - 32768
+
+  jedec,lpddr2-io-width-bits:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+      IO bus width in bits of SDRAM chip. See MR8 description in JESD209-2.
+    enum:
+      - 32
+      - 16
+      - 8
+
+  jedec,lpddr2-type:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: |
+      LPDDR type which corresponds to a number of words SDRAM pre-fetches
+      per column request. See MR8 description in JESD209-2.
+    enum:
+      - 0 # S4 (4 words prefetch architecture)
+      - 1 # S2 (2 words prefetch architecture)
+      - 2 # NVM (Non-volatile memory)

Type should not be needed but instead taken from compatible. Unless Rob
has here preference and maybe change the DDR bindings?

requiredProperties for compatible, density, io-width.

Alright