linux-kernel - Re: [PATCH v5 06/20] dt-bindings: memory: introduce DDR4

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Message-ID: <fb5083ff-4bee-4a0f-8774-54b492cd9a6d@kernel.org>
Date: Sun, 17 Aug 2025 09:19:04 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Clément Le Goffic <legoffic.clement@...il.com>,
 Rob Herring <robh@...nel.org>,
 Clément Le Goffic <clement.legoffic@...s.st.com>
Cc: Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Maxime Coquelin <mcoquelin.stm32@...il.com>,
 Alexandre Torgue <alexandre.torgue@...s.st.com>,
 Philipp Zabel <p.zabel@...gutronix.de>, Jonathan Corbet <corbet@....net>,
 Gatien Chevallier <gatien.chevallier@...s.st.com>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Gabriel Fernandez <gabriel.fernandez@...s.st.com>,
 Julius Werner <jwerner@...omium.org>, linux-arm-kernel@...ts.infradead.org,
 linux-perf-users@...r.kernel.org, devicetree@...r.kernel.org,
 linux-stm32@...md-mailman.stormreply.com, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v5 06/20] dt-bindings: memory: introduce DDR4

On 14/08/2025 16:42, Clément Le Goffic wrote:
> Hi Rob,
> 
> On 30/07/2025 23:11, Rob Herring wrote:
>> On Mon, Jul 28, 2025 at 05:29:37PM +0200, Clément Le Goffic wrote:
>>> Introduce JEDEC compliant DDR bindings, that use new memory-props binding.
>>>
>>> Signed-off-by: Clément Le Goffic <clement.legoffic@...s.st.com>
>>> ---
>>>   .../memory-controllers/ddr/jedec,ddr4.yaml         | 34 ++++++++++++++++++++++
>>>   1 file changed, 34 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/memory-controllers/ddr/jedec,ddr4.yaml b/Documentation/devicetree/bindings/memory-controllers/ddr/jedec,ddr4.yaml
>>> new file mode 100644
>>> index 000000000000..f457066a2f8b
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/memory-controllers/ddr/jedec,ddr4.yaml
>>> @@ -0,0 +1,34 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/memory-controllers/ddr/jedec,ddr4.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: DDR3 SDRAM compliant to JEDEC JESD79-4D
>>> +
>>> +maintainers:
>>> +  - Krzysztof Kozlowski <krzk@...nel.org>
>>> +
>>> +allOf:
>>> +  - $ref: jedec,sdram-props.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    items:
>>> +      - pattern: "^ddr4-[0-9a-f]{2},[0-9a-f]{1}$"
>>
>> Shouldn't this be 'jedec,ddr4-...'
> 
> That's not the case for lpddr bindings, I wanted both lpddr and ddr 
> bindings to be similar but this can change.

For LPDDR Julius introduced in commit 686fe63b2280 ("dt-bindings:
memory: Add numeric LPDDR compatible string variant") ddr4-VENDORID
pattern to distinguish individual manufacturers.

Jedec is not really the vendor here.

Is it the same case in DDR? You have a defined list of vendor IDs (also
1 byte)?

> 
>>
>>> +      - const: jedec,ddr4


Best regards,
Krzysztof