netdev - Re: [RFC v2 net-next] devlink: Add reset subcommand.

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Date:   Tue, 21 Jul 2020 14:19:43 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Vasundhara Volam <vasundhara-v.volam@...adcom.com>,
        Moshe Shemesh <moshe@...lanox.com>
Cc:     David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        Michael Chan <michael.chan@...adcom.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Pirko <jiri@...lanox.com>,
        Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [RFC v2 net-next] devlink: Add reset subcommand.

Tue, Jul 21, 2020 at 11:51:21AM CEST, vasundhara-v.volam@...adcom.com wrote:
>On Wed, Jul 1, 2020 at 3:17 PM Jiri Pirko <jiri@...nulli.us> wrote:
>>
>> Wed, Jul 01, 2020 at 11:25:50AM CEST, vasundhara-v.volam@...adcom.com wrote:
>> >On Wed, Jul 1, 2020 at 11:21 AM Jiri Pirko <jiri@...nulli.us> wrote:
>> >>
>> >> Tue, Jun 30, 2020 at 05:15:18PM CEST, vasundhara-v.volam@...adcom.com wrote:
>> >> >On Tue, Jun 30, 2020 at 6:23 PM Jiri Pirko <jiri@...nulli.us> wrote:
>> >> >>
>> >> >> Tue, Jun 30, 2020 at 01:34:06PM CEST, vasundhara-v.volam@...adcom.com wrote:
>> >> >> >Advanced NICs support live reset of some of the hardware
>> >> >> >components, that resets the device immediately with all the
>> >> >> >host drivers loaded.
>> >> >> >
>> >> >> >Add devlink reset subcommand to support live and deferred modes
>> >> >> >of reset. It allows to reset the hardware components of the
>> >> >> >entire device and supports the following fields:
>> >> >> >
>> >> >> >component:
>> >> >> >----------
>> >> >> >1. MGMT : Management processor.
>> >> >> >2. DMA : DMA engine.
>> >> >> >3. RAM : RAM shared between multiple components.
>> >> >> >4. AP : Application processor.
>> >> >> >5. ROCE : RoCE management processor.
>> >> >> >6. All : All possible components.
>> >> >> >
>> >> >> >Drivers are allowed to reset only a subset of requested components.
>> >> >>
>> >> >> I don't understand why would user ever want to do this. He does not care
>> >> >> about some magic hw entities. He just expects the hw to work. I don't
>> >> >> undestand the purpose of exposing something like this. Could you please
>> >> >> explain in details? Thanks!
>> >> >>
>> >> >If a user requests multiple components and if the driver is only able
>> >> >to honor a subset, the driver will return the components unset which
>> >> >it is able to reset.  For example, if a user requests MGMT, RAM and
>> >> >ROCE components to be reset and driver resets only MGMT and ROCE.
>> >> >Driver will unset only MGMT and ROCE bits and notifies the user that
>> >> >RAM is not reset.
>> >> >
>> >> >This will be useful for drivers to reset only a subset of components
>> >> >requested instead of returning error or silently doing only a subset
>> >> >of components.
>> >> >
>> >> >Also, this will be helpful as user will not know the components
>> >> >supported by different vendors.
>> >>
>> >> Your reply does not seem to be related to my question :/
>> >I thought that you were referring to: "Drivers are allowed to reset
>> >only a subset of requested components."
>> >
>> >or were you referring to components? If yes, the user can select the
>> >components that he wants to go for reset. This will be useful in the
>> >case where, if the user flashed only a certain component and he wants
>> >to reset that particular component. For example, in the case of SOC
>> >there are 2 components: MGMT and AP. If a user flashes only
>> >application processor, he can choose to reset only application
>> >processor.
>>
>> We already have notion of "a component" in "devlink dev flash". I think
>> that the reset component name should be in-sync with the flash.
>>
>> Thinking about it a bit more, we can extend the flash command by "reset"
>> attribute that would indicate use wants to do flash&reset right away.
>>
>> Also, thinking how this all aligns with "devlink dev reload" which we
>> currently have. The purpose of it is to re-instantiate driver instances,
>> but in case of mlxsw it means friggering FW reset as well.
>>
>> Moshe (cced) is now working on "devlink dev reload" extension that would
>> allow user to ask for a certain level of reload: driver instances only,
>> fw reset too, live fw patching, etc.
>>
>> Not sure how this overlaps with your intentions. I think it would be
>> great to see Moshe's RFC here as well so we can aligh the efforts.
>Are the patches posted yet?

I don't think so.

Moshe?