netdev - Re: [EXT] Re: [PATCH v1] net: mvpp2: divide fifo for dts-active ports only

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Date:   Mon, 23 Nov 2020 17:30:05 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Stefan Chulski <stefanc@...vell.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "thomas.petazzoni@...tlin.com" <thomas.petazzoni@...tlin.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Nadav Haklai <nadavh@...vell.com>,
        Yan Markman <ymarkman@...vell.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "mw@...ihalf.com" <mw@...ihalf.com>,
        "andrew@...n.ch" <andrew@...n.ch>
Subject: Re: [EXT] Re: [PATCH v1] net: mvpp2: divide fifo for dts-active
 ports only

On Mon, Nov 23, 2020 at 04:03:00PM +0000, Stefan Chulski wrote:
> > -----Original Message-----
> > From: Russell King - ARM Linux admin <linux@...linux.org.uk>
> > Sent: Monday, November 23, 2020 5:52 PM
> > To: Stefan Chulski <stefanc@...vell.com>
> > Cc: netdev@...r.kernel.org; thomas.petazzoni@...tlin.com;
> > davem@...emloft.net; Nadav Haklai <nadavh@...vell.com>; Yan Markman
> > <ymarkman@...vell.com>; linux-kernel@...r.kernel.org; kuba@...nel.org;
> > mw@...ihalf.com; andrew@...n.ch
> > Subject: Re: [EXT] Re: [PATCH v1] net: mvpp2: divide fifo for dts-active ports
> > only
> > 
> > On Mon, Nov 23, 2020 at 03:44:05PM +0000, Stefan Chulski wrote:
> > > Yes, but this allocation exists also in current code.
> > > From HW point of view(MAC and PPv2) maximum supported speed in CP110:
> > > port 0 - 10G, port 1 - 2.5G, port 2 - 2.5G.
> > > in CP115: port 0 - 10G, port 1 - 5G, port 2 - 2.5G.
> > >
> > > So this allocation looks correct at least for CP115.
> > > Problem that we cannot reallocate FIFO during runtime, after specific speed
> > negotiation.
> > 
> > We could do much better. DT has a "max-speed" property for ethernet
> > controllers. If we have that property, then I think we should use that to
> > determine the initialisation time FIFO allocation.
> > 
> > As I say, on Macchiatobin, the allocations we end up with are just crazy when
> > you consider the port speeds that the hardware supports.
> > Maybe that should be done as a follow-on patch - but I think it needs to be
> > done.
> 
> I agree with you. We can use "max-speed" for better FIFO allocations.
> I plan to upstream more fixes from the "Marvell" devel branch then I can prepare this patch.
> So you OK with this patch and then follow-on improvement?

Yes - but I would like to see the commit description say that this
results in no change the situation where all three ports are in use.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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