linux-kernel - Re: [PATCH v2 1/3] dt-bindings: reserved-memory: ramoops: Update the binding

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Message-ID: <fb4fafef-4aed-5333-4ed9-5335250541f3@quicinc.com>
Date:   Fri, 13 Jan 2023 18:52:31 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        <keescook@...omium.org>, <gpiccoli@...lia.com>, <corbet@....net>,
        <tony.luck@...el.com>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>
CC:     <linux-hardening@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] dt-bindings: reserved-memory: ramoops: Update the
 binding

Hi Krzysztof,

On 1/13/2023 5:34 PM, Krzysztof Kozlowski wrote:
> Subject: drop second/last, redundant "binding". The "dt-bindings" prefix
> is already stating that these are bindings.
> 
> Your subject says nothing. Everything is "update".
> 

I will fix this.

> On 13/01/2023 12:58, Mukesh Ojha wrote:
>> Update the ramoops region binding document with details
>> like region can also be reserved dynamically apart from
>> reserving it statically.
>  > So what exactly can be here reserved dynamically? And what does it mean
> 'dynamically'? By whom? How is this property of hardware (not OS)?
> 
Normally, for ramoops, already known physical address range from DDR are 
mentioned in Device tree which gets reserved from reserved-memory kernel 
framework(example 1 in this file).

By being dynamic, I meant, with this we are letting the framework to get 
the size from a range of allowable address (<0x0 0x00000000 0xffffffff 
0xffffffff>).

Let me know, if you need more detail.

>>
>> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
>> ---
>> Change in v2:
>>    - Added this patch as per changes going to be done in patch 3/3
>>
>>   .../bindings/reserved-memory/ramoops.yaml          | 34 ++++++++++++++++++++--
>>   1 file changed, 32 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml b/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
>> index 0391871..54e46e8 100644
>> --- a/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
>> +++ b/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
>> @@ -10,7 +10,8 @@ description: |
>>     ramoops provides persistent RAM storage for oops and panics, so they can be
>>     recovered after a reboot. This is a child-node of "/reserved-memory", and
>>     is named "ramoops" after the backend, rather than "pstore" which is the
>> -  subsystem.
>> +  subsystem. This region can be reserved both statically or dynamically by
>> +  using appropriate property in device tree.
>>   
>>     Parts of this storage may be set aside for other persistent log buffers, such
>>     as kernel log messages, or for optional ECC error-correction data.  The total
>> @@ -112,7 +113,13 @@ unevaluatedProperties: false
>>   
>>   required:
>>     - compatible
>> -  - reg
>> +
>> +oneOf:
>> +  - required:
>> +      - reg
>> +
>> +  - required:
>> +      - size
> 
> There is no such property. You cannot require it.

Forgot to mention this.

--- a/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
+++ b/Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
@@ -37,6 +37,20 @@ properties:
    reg:
      description: region of memory that is preserved between reboots

+  size:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    minItems: 1
+    maxItems: 2
+    description: >
+      Length based on parent's \#size-cells. Size in bytes of memory to
+      reserve.
+
+  alloc-ranges:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description: >
+      Address and Length pairs. Specifies regions of memory that are
+      acceptable to allocate from.
+
    ecc-size:
      $ref: /schemas/types.yaml#/definitions/uint32
      description: enables ECC support and specifies ECC buffer size in 
bytes
@@ -119,6 +133,7 @@ oneOf:
        - reg

    - required:
+      - alloc-ranges
        - size
> 
>>   
>>   anyOf:
>>     - required: [record-size]
>> @@ -142,3 +149,26 @@ examples:
>>               };
>>           };
>>       };
>> +
>> +  - |
>> +    / {
>> +        compatible = "foo";
>> +        model = "foo";
>> +        #address-cells = <2>;
>> +        #size-cells = <2>;
>> +
>> +        reserved-memory {
>> +            #address-cells = <2>;
>> +            #size-cells = <2>;
>> +            ranges;
>> +
>> +            ramoops: ramoops_region {
> 
> Node names should be generic, no underscores in node names.
> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation
> 

Thanks.

> Any reason in naming it differently then existing one? You have there
> example.

ramoops@...f0000 is not valid after dynamic allocation of memory.
Probably, will mention it as

ramoops_region: ramoops { ??

-Mukesh
> 
>> +                compatible = "ramoops";
>> +                alloc-ranges = <0x0 0x00000000 0xffffffff 0xffffffff>;
>> +                size = <0x0 0x10000>;       /* 64kB */
>> +                console-size = <0x8000>;    /* 32kB */
>> +                record-size = <0x400>;      /*  1kB */
>> +                ecc-size = <16>;
>> +            };
>> +        };
>> +    };
> 
> Best regards,
> Krzysztof
>