netdev - Re: [RFC PATCH net-next] net: dsa: mt7530: support setting ageing time

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Date:   Fri, 20 Nov 2020 11:37:53 +0800
From:   DENG Qingfang <dqfext@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev <netdev@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Russell King <linux@...linux.org.uk>,
        René van Dorst <opensource@...rst.com>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Greg Ungerer <gerg@...nel.org>,
        Alex Dewar <alex.dewar90@...il.com>,
        Chuanhong Guo <gch981213@...il.com>
Subject: Re: [RFC PATCH net-next] net: dsa: mt7530: support setting ageing time

On Fri, Nov 20, 2020 at 10:26 AM Andrew Lunn <andrew@...n.ch> wrote:
> The bridge code will default to 300 seconds. And after a topology
> change, it sets it to 2 * the forwarding delay, which defaults to 15
> seconds. So maybe you can look for these two values, and use
> pre-computed values?

15 and 300 are not larger than 4096 (AGE_UNIT_MAX + 1) so the exact
match can always be found in the first iteration:

age_count = 0, age_unit = 14, secs = (0 + 1) * (14 + 1) = 15
age_count = 0, age_unit = 299, secs = (0 + 1) * (299 + 1) = 300

>
> You still need to handle other values, the user can configure these.
>
>              Andrew