linux-kernel - Re: [PATCH v2] net: phy: workaround for buggy cable detection by LAN8700 after cable plugging

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Date:	Fri, 14 Aug 2015 20:12:15 +0300
From:	Igor Plyatov <plyatov@...il.com>
To:	Michael Heimpold <mhei@...mpold.de>
CC:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	f.fainelli@...il.com, joe@...ches.com, luwei.zhou@...escale.com,
	richardcochran@...il.com, davem@...emloft.net,
	u.kleine-koenig@...gutronix.de, Fabio.Estevam@...escale.com,
	LW@...o-electronics.de, Frank.Li@...escale.com
Subject: Re: [PATCH v2] net: phy: workaround for buggy cable detection by
 LAN8700 after cable plugging

Dear Michael,

> The LAN8700, LAN8710, LAN8720 is a product of the SMSC company.
> Microchip acquired SMSC in August 2012.
>
> The LAN8700 is a legacy product for Microchip and they will not update
> anything about it. So, even if Microchip know about HW bug, then there
> is no chance to have Errata sheet or any new documents about LAN8700.
> Long time ago, I worked on a custom device with a PHY of the same family.
> Errata sheet existed but was only available by signing a NDA. So I simply
> wondered whether this changed since SMSC is now Microchip or if they keep
> it still so covered...

The Microchip web-site does not contain Errata sheet for LAN87xx devices.
While it contains many Errata sheets for PIC and dsPIC devices.
So, situation is same as many years ago.


> I propose following comment for the lan87xx_read_status():
> /*
>    * The LAN87xx suffers from rare absence of the ENERGYON-bit when
> Ethernet cable
>    * plugs in while LAN87xx is in Energy Detect Power-Down mode. This
> leads to
>    * unstable detection of plugging in Ethernet cable.
>    * This workaround disables Energy Detect Power-Down mode and waiting for
>    * response on link pulses to detect presence of plugged Ethernet cable.
>    * The Energy Detect Power-Down mode enabled again in the end of
> procedure to
>    * save approximately 220 mW of power if cable is unplugged.
>    */
> Nice. Only one nitpick: ... _is_ enabled again...
>

Changed in [PATCH v3].

Best wishes.
--
Igor Plyatov
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