netdev - Re: [RFC v2, net-next, PATCH 4/4] net/cpsw_switchdev: add switchdev mode of operation on cpsw driver

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Date:   Wed, 20 Jun 2018 14:53:47 +0200
From:   Ivan Vecera <ivecera@...hat.com>
To:     Jiri Pirko <jiri@...nulli.us>,
        Grygorii Strashko <grygorii.strashko@...com>
Cc:     Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        netdev@...r.kernel.org, ivan.khoronzhuk@...aro.org, nsekhar@...com,
        andrew@...n.ch, f.fainelli@...il.com, francois.ozog@...aro.org,
        yogeshs@...com, spatton@...com, Jose.Abreu@...opsys.com
Subject: Re: [RFC v2, net-next, PATCH 4/4] net/cpsw_switchdev: add switchdev
 mode of operation on cpsw driver

On 20.6.2018 09:08, Jiri Pirko wrote:
> Tue, Jun 19, 2018 at 01:19:00AM CEST, grygorii.strashko@...com wrote:
>>
>>
>> On 06/14/2018 06:43 AM, Ilias Apalodimas wrote:
>>> On Thu, Jun 14, 2018 at 01:39:58PM +0200, Jiri Pirko wrote:
>>>> Thu, Jun 14, 2018 at 01:34:04PM CEST, ilias.apalodimas@...aro.org wrote:
>>>>> On Thu, Jun 14, 2018 at 01:30:28PM +0200, Jiri Pirko wrote:
>>>>>> Thu, Jun 14, 2018 at 01:11:30PM CEST, ilias.apalodimas@...aro.org wrote:
>>>>>>
>>>>>> [...]
>>>>>>
>>>>>>> @@ -2711,6 +2789,10 @@ static int cpsw_probe_dt(struct cpsw_platform_data *data,
>>>>>>> 	if (of_property_read_bool(node, "dual_emac"))
>>>>>>> 		data->switch_mode = CPSW_DUAL_EMAC;
>>>>>>>
>>>>>>> +	/* switchdev overrides DTS */
>>>>>>> +	if (IS_ENABLED(CONFIG_TI_CPSW_SWITCHDEV))
>>>>>>> +		data->switch_mode = CPSW_SWITCHDEV;
>>>>>>
>>>>>> So you force CPSW_SWITCHDEV mode if the CONFIG_TI_CPSW_SWITCHDEV is
>>>>>> enabled. That does not sound right. I think that user should tell what
>>>>>> mode does he want regardless what the kernel config is.
>>>>> We discussed this during the V1 of the RFC. Yes it doesn't seem good, but the
>>>>> device currently configures the modes using DTS (which is not correct). I choose
>>>>> the .config due to that. I can't think of anything better, but i am open to
>>>>> suggestions
>>>>
>>>> Agreed that DTS does fit as well. I think that this might be a job for
>>>> devlink parameters (patchset is going to be sent upstream next week).
>>>> You do have 1 bus address for the whole device (both ports), right?
>>>>
>>> Yes devlink sounds reasonable. I thyink there's only one bus for it, but then
>>> again i am far from an expert on the hardware interrnals. Grygorii can correct
>>> me if i am wrong.
>>
>> Devlink and NFS boot are not compatible as per my understanding, so .. 
> 
> ? Why do you say so?

Why aren't they compatible?? You can have devlink binary in initramfs and
configure the ASIC and ports via devlink batch file - prior mounting NFS root.

>>
>> Again, current driver, as is, supports NFS boot in all modes
>> (how good is the cur driver is question which out of scope of this discussion).
>>
>> And we discussed this in RFC v1 - driver mode selection will be changed 
>> if we will proceed and it will be new driver for proper switch support.
>>
>> Not sure about about Devlink (need to study it and we never got any requests from end
>> users for this as I know), and I'd like to note (again) that this is embedded 
>> (industrial/automotive etc), so everything preferred to be simple, fast and
>> preferably configured statically (in most of the cases end users what boot time 
>> configuration).
> 
> You need to study it indeed.
> 
>>
>> -- 
>> regards,
>> -grygorii