netdev - Re: [PATCH v4 1/3] dsa: marvell: Provide per device information about max frame size

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Message-ID: <20230125122412.4eb1746d@wsk>
Date:   Wed, 25 Jan 2023 12:24:12 +0100
From:   Lukasz Majewski <lukma@...x.de>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Vladimir Oltean <olteanv@...il.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/3] dsa: marvell: Provide per device information
 about max frame size

Hi,

> Hi Russell,
> 
> > On Fri, Jan 06, 2023 at 11:16:49AM +0100, Lukasz Majewski wrote:  
> > > Different Marvell DSA switches support different size of max frame
> > > bytes to be sent. This value corresponds to the memory allocated
> > > in switch to store single frame.
> > > 
> > > For example mv88e6185 supports max 1632 bytes, which is now
> > > in-driver standard value. On the other hand - mv88e6250 supports
> > > 2048 bytes. To be more interresting - devices supporting jumbo
> > > frames - use yet another value (10240 bytes)
> > > 
> > > As this value is internal and may be different for each switch IC,
> > > new entry in struct mv88e6xxx_info has been added to store it.
> > > 
> > > This commit doesn't change the code functionality - it just
> > > provides the max frame size value explicitly - up till now it has
> > > been assigned depending on the callback provided by the IC driver
> > > (e.g. .set_max_frame_size, .port_set_jumbo_size).    
> > 
> > I don't think this patch is correct.
> > 
> > One of the things that mv88e6xxx_setup_port() does when initialising
> > each port is:
> > 
> >         if (chip->info->ops->port_set_jumbo_size) {
> >                 err = chip->info->ops->port_set_jumbo_size(chip,
> > port, 10218); if (err)
> >                         return err;
> >         }
> > 
> > There is one implementation of this, which is
> > mv88e6165_port_set_jumbo_size() and that has the effect of setting
> > port register 8 to the largest size. So any chip that supports the
> > port_set_jumbo_size() method will be programmed on initialisation to
> > support this larger size.
> > 
> > However, you seem to be listing e.g. the 88e6190 (if I'm
> > interpreting the horrid mv88e6xxx_table changes correctly)  
> 
> Those changes were requested by the community. Previous versions of
> this patch were just changing things to allow correct operation of the
> switch ICs on which I do work (i.e. 88e6020 and 88e6071).
> 
> And yes, for 88e6190 the max_frame_size = 10240, but (by mistake) the
> same value was not updated for 88e6190X.
> 
> The question is - how shall I proceed? 
> 
> After the discussion about this code - it looks like approach from v3
> [1] seems to be the most non-intrusive for other ICs.
> 

I would appreciate _any_ hints on how shall I proceed to prepare those
patches, so the community will accept them...

Thanks in advance.

> > as having a maximum
> > frame size of 1522, but it implements this method, supports 10240,
> > and thus is programmed to support frames of that size rather than
> > 1522. 
> 
> Links:
> 
> [1] - https://lore.kernel.org/netdev/Y7M+mWMU+DJPYubp@lunn.ch/T/
> 
> 
> Best regards,
> 
> Lukasz Majewski
> 
> --
> 
> DENX Software Engineering GmbH,      Managing Director: Erika Unter
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> lukma@...x.de




Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@...x.de

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