linux-kernel - Re: [PATCH net-next 3/5] net: mvpp2: use a data size of 10kB for Tx FIFO on port 0

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Message-ID: <20180302171117.2344a893@windsurf.lan>
Date:   Fri, 2 Mar 2018 17:11:17 +0100
From:   Thomas Petazzoni <thomas.petazzoni@...tlin.com>
To:     Antoine Tenart <antoine.tenart@...tlin.com>
Cc:     davem@...emloft.net, Yan Markman <ymarkman@...vell.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        maxime.chevallier@...tlin.com, gregory.clement@...tlin.com,
        miquel.raynal@...tlin.com, nadavh@...vell.com, stefanc@...vell.com,
        mw@...ihalf.com
Subject: Re: [PATCH net-next 3/5] net: mvpp2: use a data size of 10kB for Tx
 FIFO on port 0

Hello,

On Fri,  2 Mar 2018 16:40:42 +0100, Antoine Tenart wrote:

> -/* Initialize Tx FIFO's */
> +/* Initialize Tx FIFO's
> + * The CP110's total tx-fifo size is 19kB.
> + * Use large-size 10kB for fast port but 3kB for others.
> + */

Is there a reason to hardcode 10KB for port 0, and 3KB for the other
ports ? Would there be use cases where the user may want different
configurations ?

It's just that it feels very "hardcoded" to enforce specifically those
numbers.

Also, does it make sense to mention the CP110 here ? Is this 19 KB
limitation a limit of the PPv2.2 IP, or of the CP110 ?

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com