netdev - Re: [PATCH v3 net-next 01/10] net: mscc: ocelot: auto-detect packet buffer size and number of frame references

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Date:   Fri, 8 Jan 2021 10:30:00 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>, netdev@...r.kernel.org
Cc:     alexandre.belloni@...tlin.com, andrew@...n.ch,
        vivien.didelot@...il.com, alexandru.marginean@....com,
        claudiu.manoil@....com, xiaoliang.yang_1@....com,
        hongbo.wang@....com, kuba@...nel.org, jiri@...nulli.us,
        idosch@...sch.org, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH v3 net-next 01/10] net: mscc: ocelot: auto-detect packet
 buffer size and number of frame references



On 1/8/2021 9:59 AM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> Instead of reading these values from the reference manual and writing
> them down into the driver, it appears that the hardware gives us the
> option of detecting them dynamically.
> 
> The number of frame references corresponds to what the reference manual
> notes, however it seems that the frame buffers are reported as slightly
> less than the books would indicate. On VSC9959 (Felix), the books say it
> should have 128KB of packet buffer, but the registers indicate only
> 129840 bytes (126.79 KB). Also, the unit of measurement for FREECNT from
> the documentation of all these devices is incorrect (taken from an older
> generation). This was confirmed by Younes Leroul from Microchip support.
> 
> Not having anything better to do with these values at the moment* (this
> will change soon), let's just print them.
> 
> *The frame buffer size is, in fact, used to calculate the tail dropping
> watermarks.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian