linux-kernel - Re: [PATCH 4/7] MIPS: Octeon: Add Free Pointer Unit (FPA) support.

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Message-ID: <70fa7ec2-3e6d-e420-ff57-b34dc7ec311e@gmail.com>
Date:   Thu, 2 Nov 2017 11:04:26 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     David Daney <ddaney@...iumnetworks.com>,
        David Daney <david.daney@...ium.com>,
        linux-mips@...ux-mips.org, ralf@...ux-mips.org,
        James Hogan <james.hogan@...s.com>, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org,
        "Steven J. Hill" <steven.hill@...ium.com>,
        devicetree@...r.kernel.org, Carlos Munoz <cmunoz@...ium.com>
Subject: Re: [PATCH 4/7] MIPS: Octeon: Add Free Pointer Unit (FPA) support.

On 11/02/2017 09:27 AM, David Daney wrote:
> On 11/01/2017 08:29 PM, Florian Fainelli wrote:
>> Le 11/01/17 à 17:36, David Daney a écrit :
>>> From: Carlos Munoz <cmunoz@...ium.com>
>>>
>>>  From the hardware user manual: "The FPA is a unit that maintains
>>> pools of pointers to free L2/DRAM memory. To provide QoS, the pools
>>> are referenced indirectly through 1024 auras. Both core software
>>> and hardware units allocate and free pointers."
>>
>> This looks like a possibly similar implement to what
>> drivers/net/ethernet/marvell/mvneta_bm.c, can you see if you can make
>> any use of genpool_* and include/net/hwbm.h here as well?
> 
> Yikes!  Is it permitted to put function definitions that are not "static
> inline" in header files?

Meh well, this is not even ressembling what we initially discussed, so I
was hoping we could build more interesting features on top of this.

> 
> The driver currently doesn't use page fragments, so I don't think that
> the hwbm thing can be used.
> 
> Also the FPA unit is used to control RED and back pressure in the PKI
> (packet input processor), which are features that are features not
> considered in hwbm.
> 
> The OCTEON-III hardware also uses the FPA for non-packet-buffer memory
> allocations.  So for those, it seems that hwbm is also not a good fit.

OK, let me see if I understand how FPA works, can we say that this is
more or less a buffer tokenizer in that, you give it a buffer physical
address and it returns an unique identifier that the FPA uses for actual
packet passing, transmission and other manipulations?

There were a few funky things in the network driver, I will comment there.
--
Florian