linux-kernel - Re: [PATCH 1/4] dt-bindings: misc: tmr-manager: Add device-tree binding for TMR Manager

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Date:   Wed, 29 Jun 2022 12:37:23 +0000
From:   "Rao, Appana Durga Kedareswara" 
        <appana.durga.kedareswara.rao@....com>
To:     "Simek, Michal" <michal.simek@....com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Appana Durga Kedareswara rao <appana.durga.rao@...inx.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "derek.kiernan@...inx.com" <derek.kiernan@...inx.com>,
        "dragan.cvetic@...inx.com" <dragan.cvetic@...inx.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     "git (AMD-Xilinx)" <git@....com>, "git@...inx.com" <git@...inx.com>
Subject: Re: [PATCH 1/4] dt-bindings: misc: tmr-manager: Add device-tree
 binding for TMR Manager

Hi,


On 29/06/22 5:29 pm, Michal Simek wrote:
> 
> 
> On 6/29/22 13:45, Krzysztof Kozlowski wrote:
>> On 29/06/2022 13:23, Michal Simek wrote:
>>>
>>>
>>> On 6/29/22 12:07, Krzysztof Kozlowski wrote:
>>>> On 28/06/2022 07:43, Appana Durga Kedareswara rao wrote:
>>>>> This commit adds documentation for Triple Modular Redundancy(TMR) 
>>>>> Manager
>>>>> IP. The Triple Modular Redundancy(TMR) Manager is responsible for 
>>>>> handling
>>>>> the TMR subsystem state, including fault detection and error recovery
>>>>> provides soft error detection, correction and recovery features.
>>>>>
>>>>> Signed-off-by: Appana Durga Kedareswara rao 
>>>>> <appana.durga.rao@...inx.com>
>>>>> ---
>>>>>    .../bindings/misc/xlnx,tmr-manager.yaml       | 48 
>>>>> +++++++++++++++++++
>>>>
>>>> This is not a misc device. Find appropriate subsystem for it. It's not
>>>> EDAC, right?
>>>
>>> We were thinking where to put it but it is not EDAC driver.
>>> If you have better suggestion for subsystem please let us know.
>>
>> I don't know what's the device about. The description does not help:
>>
>> "TMR Manager is responsible for TMR subsystem state..."
> 
> ok. let's improve commit message in v2.

Sure will improve the commit message in v2.
> 
> TMR - triple module redundancy.
> 
> You design the system with one CPU which is default microblaze 
> configuration with interrupt controller, timer and other IPs.
> 
> And then say I want to do it triple redundant with all that voting, etc.
> If you want to get all details you can take a look at this guide
> 
> https://www.xilinx.com/content/dam/xilinx/support/documents/ip_documentation/tmr/v1_0/pg268-tmr.pdf 
> 
> 
> In short TMR manager is servicing all that 3 cores and making sure that 
> they are all running in sync. If not it has capability recover the 
> system. It means cpu gets to break handler (it is the part of microblaze 
> series) and it restarts all cpus.
> 
> And TMR inject driver is module which is capable to inject error to 
> internal memory to cause the exception to exercise that recovery code.
> 
> Kedar: Feel free to correct me or add more details.

Thanks Michal for the detailed explanation.

The Triple Modular Redundancy(TMR) subsystem has three Microblaze 
processor instances, If any one of the Microblaze processors goes to an 
unknown state due to fault injection break handler will get called, 
which in turn calls the tmr manager driver API to perform recovery.
like Michal said TMR inject driver is capable of inject error to
internal memory to cause fault in one the Microblaze processor

@Krzysztof : please let me know if more information required about
this TMR subsystem will provide.

Regards,
Kedar.


> 
> Thanks,
> Michal