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 13:59:32 +0200
From:   Michal Simek <michal.simek@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Appana Durga Kedareswara rao <appana.durga.rao@...inx.com>,
        <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <michal.simek@...inx.com>, <derek.kiernan@...inx.com>,
        <dragan.cvetic@...inx.com>, <arnd@...db.de>,
        <gregkh@...uxfoundation.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <git@....com>, <git@...inx.com>
Subject: Re: [PATCH 1/4] dt-bindings: misc: tmr-manager: Add device-tree
 binding for TMR Manager



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.

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