netdev - Re: [PATCH net] net: phy: ensure PHY is powered up when reading ID registers

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Message-Id: <20190107.071858.919470138587464515.davem@davemloft.net>
Date:   Mon, 07 Jan 2019 07:18:58 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     hkallweit1@...il.com
Cc:     f.fainelli@...il.com, andrew@...n.ch, netdev@...r.kernel.org
Subject: Re: [PATCH net] net: phy: ensure PHY is powered up when reading ID
 registers

From: Heiner Kallweit <hkallweit1@...il.com>
Date: Sat, 5 Jan 2019 14:21:03 +0100

> During a bug analysis we came across the fact that there's no guarantee
> that reading from the ID registers returns a valid value if PHY is
> powered down. When reading invalid values we may load no or the wrong
> PHY driver. Therefore let's play safe and power up the PHY before
> reading the ID registers in case PHY is powered down.
> 
> Suggested-by: Florian Fainelli <f.fainelli@...il.com>
> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>

There are several concerns still being discussed with this patch.

I personally don't like the idea that this can leave the PHY powered up
fully on a misprobe, and the unexpected power draw that might create.

Anyways, I'm marking this as changes requested.  If anything, some more
discussion should be added to the commit message even if the patch itself
remains the same.

There has been a lot of enlightening information in that thread, and at
least in a condensed state that needs to end up in the commit message.

Thanks.