From: Saravana Kannan <saravanak@google.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>,
Rob Herring <robh+dt@kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
netdev@vger.kernel.org, kernel-team@android.com,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
Neil Armstrong <narmstrong@baylibre.com>,
linux-amlogic@lists.infradead.org
Subject: Re: [PATCH v2] of: property: fw_devlink: Add support for "phy-handle" property
Date: Mon, 23 Aug 2021 13:48:23 -0700 [thread overview]
Message-ID: <CAGETcx8j+bOPL_-qFzHHJkX41Ljzq8HBkbBqtd4E0-2u6a3_Hg@mail.gmail.com> (raw)
In-Reply-To: <YSP91FfbzUHKiv+L@lunn.ch>
On Mon, Aug 23, 2021 at 12:58 PM Andrew Lunn <andrew@lunn.ch> wrote:
>
> > PHY seems to be one of those cases where it's okay to have the
> > compatible property but also okay to not have it.
>
> Correct. They are like PCI or USB devices. You can ask it, what are
> you? There are two registers in standard locations which give you a
> vendor and product ID. We use that to find the correct driver.
For all the cases of PHYs that currently don't need any compatible
string, requiring a compatible string of type "ethernet-phy-standard"
would have been nice. That would have made PHYs consistent with the
general DT norm of "you need a compatible string to be matched with
the device". Anyway, it's too late to do that now. So I'll have to
deal with this some other way (I have a bunch of ideas, so it's not
the end of the world).
> You only need a compatible when things are not so simple.
>
> 1) The IDs are wrong. Some silicon vendors do stupid things
>
> 2) Chicken/egg problems, you cannot read the ID registers until you
> load the driver and some resource is enabled.
>
> 3) It is a C45 devices, e.g. part of clause 45 of 802.3, which
> requires a different protocol to be talked over the bus. So the
> compatible string tells you to talk C45 to get the IDs.
>
> 4) It is not a PHY, but some sort of other MDIO device, and hence
> there are no ID registers.
Yeah, I was digging through of_mdiobus_child_is_phy() when I was doing
the mdio-mux fixes and noticed this. But I missed/forgot the mdiobus
doesn't probe part when I sent out the phy-handle patch.
-Saravana
next prev parent reply other threads:[~2021-08-23 20:49 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-18 2:17 [PATCH v2] of: property: fw_devlink: Add support for "phy-handle" property Saravana Kannan
2021-08-18 17:00 ` Rob Herring
[not found] ` <CGME20210823120849eucas1p11d3919886444358472be3edd1c662755@eucas1p1.samsung.com>
2021-08-23 12:08 ` Marek Szyprowski
2021-08-23 12:42 ` Rob Herring
2021-08-23 13:16 ` Andrew Lunn
2021-08-23 18:13 ` Saravana Kannan
2021-08-23 19:50 ` Andrew Lunn
2021-08-24 6:52 ` Marek Szyprowski
2021-08-23 18:22 ` Saravana Kannan
2021-08-23 19:58 ` Andrew Lunn
2021-08-23 20:48 ` Saravana Kannan [this message]
2021-08-23 22:01 ` Andrew Lunn
2021-08-23 22:08 ` Rob Herring
2021-08-24 7:03 ` Marek Szyprowski
2021-08-24 7:31 ` Saravana Kannan
2021-09-01 2:37 ` Saravana Kannan
2021-09-01 7:22 ` Marek Szyprowski
2021-09-08 21:58 ` [PATCH v1] RFC: of: property: fix phy-hanlde issue Saravana Kannan
2021-09-09 8:03 ` Marek Szyprowski
2021-09-14 0:54 ` Saravana Kannan
2021-09-14 4:44 ` Saravana Kannan
2021-09-14 6:15 ` Marek Szyprowski
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