From: Florian Fainelli <f.fainelli@gmail.com>
To: Andrew Lunn <andrew@lunn.ch>,
Claudiu Beznea <claudiu.beznea@microchip.com>
Cc: hkallweit1@gmail.com, linux@armlinux.org.uk, robh+dt@kernel.org,
frowand.list@gmail.com, netdev@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] of: of_mdio: count number of regitered phys
Date: Mon, 29 Jun 2020 20:35:11 -0700 [thread overview]
Message-ID: <6b022bcc-a670-da1d-5f5a-bdf4af667652@gmail.com> (raw)
In-Reply-To: <20200630004543.GB597495@lunn.ch>
On 6/29/2020 5:45 PM, Andrew Lunn wrote:
> On Mon, Jun 29, 2020 at 10:26:36AM +0300, Claudiu Beznea wrote:
>> In case of_mdiobus_register_phy()/of_mdiobus_register_device()
>> returns -ENODEV for all PHYs in device tree or for all scanned
>> PHYs there is a chance that of_mdiobus_register() to
>> return success code although no PHY devices were registered.
>> Add a counter that increments every time a PHY was registered
>> to avoid the above scenario.
>
> Hi Claudiu
>
> There is a danger here this will break something. Without this patch,
> an empty bus is O.K. But with this patch, a bus without a PHY is a
> problem.
>
> Take for example FEC. It often comes in pairs. Each has an MDIO
> bus. But to save pins, there are some designs which place two PHYs on
> one bus, leaving the other empty. The driver unconditionally calls
> of_mdiobus_register() and if it returns an error, it will error out
> the probe. So i would not be too surprised if you get reports of
> missing interfaces with this patch.
Agreed, the potential for breakage here is too high especially given
this is fixing a hypothetical problem rather an an actual one. Even if
we were taking this from the angle of power management, runtime PM
should ensure that a MDIO bus with no slave, or no activity gets runtime
suspended.
--
Florian
next prev parent reply other threads:[~2020-06-30 3:35 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-29 7:26 [PATCH] of: of_mdio: count number of regitered phys Claudiu Beznea
2020-06-30 0:45 ` Andrew Lunn
2020-06-30 3:35 ` Florian Fainelli [this message]
2020-07-01 8:47 ` Claudiu.Beznea
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6b022bcc-a670-da1d-5f5a-bdf4af667652@gmail.com \
--to=f.fainelli@gmail.com \
--cc=andrew@lunn.ch \
--cc=claudiu.beznea@microchip.com \
--cc=devicetree@vger.kernel.org \
--cc=frowand.list@gmail.com \
--cc=hkallweit1@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=netdev@vger.kernel.org \
--cc=robh+dt@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).