linux-kernel - Re: [PATCH v5 3/9] dt-bindings: memory: lpddr2: Add revision-id properties

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Message-ID: <c33c9de2-ff0f-0ba7-b424-728d316dcca2@gmail.com>
Date:   Wed, 9 Feb 2022 14:49:10 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Julius Werner <jwerner@...omium.org>
Cc:     Rob Herring <robh@...nel.org>, linux-tegra@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>
Subject: Re: [PATCH v5 3/9] dt-bindings: memory: lpddr2: Add revision-id
 properties

09.02.2022 11:58, Krzysztof Kozlowski пишет:
> On 09/02/2022 00:46, Julius Werner wrote:
>>> Unfortunately I have no clue what patch you talk about ("this patch").
>>> There is no context here, no link except the older LPDDR3.
>>
>> Sorry, I tried to reply to
>> https://lore.kernel.org/all/20211006224659.21434-4-digetx@gmail.com/
>> ([PATCH v5 3/9] dt-bindings: memory: lpddr2: Add revision-id
>> properties) and was hoping that would automatically provide context.
>> That patch added two one-cell properties `revision-id1` and
>> `revision-id2` to "jedec,lpddr2". Earlier in
>> https://www.spinics.net/lists/devicetree/msg413733.html ([PATCH]
>> dt-bindings: ddr: Add optional manufacturer and revision ID to
>> LPDDR3), I had added a single two-cell property `revision-id` for the
>> same purpose to "jedec,lpddr3".
>>
>> I think it would be better if this was consistent between the two
>> types of LPDDR memory. Should I just send a patch that replaces the
>> two revision IDs in "jedec,lpddr2" with a single one according to the
>> principle of "jedec,lpddr3"? Or is it too late for that now and the
>> binding already considered stable and unchangeable?
> 
> Hi Julius,
> 
> Having same bindings for revision ID makes sense. Sadly this was not
> spotted during review, eh, life... Unfortunately the bindings are
> already in a mainline release, so they are considered stable. You can
> however bring patches (bindings + drivers/memory/of + dts) which make
> the revision-id[12] deprecated and introduce new revision-id.
> 
> It should be something similar to what I did for max-freq:
> https://lore.kernel.org/all/20220206135807.211767-7-krzysztof.kozlowski@canonical.com/
> 
> Dmitry,
> Any early comments on such approach from you?

I don't mind, but I also don't see where the revision-id property of
LPDDR3 is used at all. I can't find any device-tree with LPDDR3
revision-id and don't see it being used in the code either. Maybe it's
the LPDDR3 binding that needs to be changed?
I made each LPDDR2 revision-id property to correspond to a dedicated MR
of LPDDR, which feels okay to me to since it matches h/w.