linux-kernel - Re: [Patch v6 3/4] dt-bindings: memory: Update reg maxitems for tegra186

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Message-ID: <3c80282b-0d63-1e1f-1036-1c8e79f1cbbc@collabora.com>
Date:   Tue, 12 Apr 2022 01:28:41 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Ashish Mhetre <amhetre@...dia.com>,
        Dmitry Osipenko <digetx@...il.com>,
        krzysztof.kozlowski@...aro.org, thierry.reding@...il.com,
        jonathanh@...dia.com, robh+dt@...nel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, krzysztof.kozlowski+dt@...aro.org
Cc:     vdumpa@...dia.com, Snikam@...dia.com
Subject: Re: [Patch v6 3/4] dt-bindings: memory: Update reg maxitems for
 tegra186

On 4/11/22 18:41, Ashish Mhetre wrote:
> 
> 
> On 4/11/2022 8:59 PM, Dmitry Osipenko wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> On 4/11/22 18:02, Ashish Mhetre wrote:
>>>
>>>
>>> On 4/10/2022 7:51 PM, Dmitry Osipenko wrote:
>>>> External email: Use caution opening links or attachments
>>>>
>>>>
>>>> 06.04.2022 08:24, Ashish Mhetre пишет:
>>>>>            memory-controller@...0000 {
>>>>>                compatible = "nvidia,tegra186-mc";
>>>>> -            reg = <0x0 0x02c00000 0x0 0xb0000>;
>>>>> +            reg = <0x0 0x02c00000 0x0 0x10000>,    /* MC-SID */
>>>>> +                  <0x0 0x02c10000 0x0 0x10000>,    /* Broadcast
>>>>> channel */
>>>>> +                  <0x0 0x02c20000 0x0 0x10000>,    /* MC0 */
>>>>> +                  <0x0 0x02c30000 0x0 0x10000>,    /* MC1 */
>>>>> +                  <0x0 0x02c40000 0x0 0x10000>,    /* MC2 */
>>>>> +                  <0x0 0x02c50000 0x0 0x10000>;    /* MC3 */
>>>>> +            reg-names = "mc-sid", "mc-broadcast", "mc0", "mc1",
>>>>> "mc2", "mc3";
>>>>
>>>> The "mc-" prefix feels redundant to me, I'd name the regs like this:
>>>>
>>>>     "sid", "broadcast", "ch0", "ch1", "ch2", "ch3"
>>>>
>>>>
>>>> You should also add validation of the regs/reg-names to the yaml based
>>>> on SoC version. I.e. it's not enough to only bump the maxItems.
>>>
>>> Okay, I will add validation of reg-names as following:
>>>
>>>    reg-names:
>>>      minItems: 0
>>>      maxItems: 6
>>>      items:
>>>        - const: sid
>>>        - const: broadcast
>>>        - const: ch0
>>>        - const: ch1
>>>        - const: ch2
>>>        - const: ch3
>>>
>>>
>>> We will have to keep minItems to 0 in order to make it compatible with
>>> old DT, right?
>>
>> Bindings are about the latest DTs. In general older dtbs must be updated
>> and you must get error from the schema checker for older DTs. It's only
>> drivers that should care about older dtbs.
> 
> On v5 Krzysztof mentioned that old DTS will start failing with new
> bindings https://lkml.org/lkml/2022/3/22/907.
> So I just wanted to confirm whether it's fine if updated bindings
> start to fail with old DTS?

Since the older DT was incorrect, it's fine that the DT check will fail
for it.