linux-kernel - Re: [PATCH devicetree 2/2] MIPS: mscc: ocelot: mark the phy-mode for internal PHY ports

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Message-ID: <20210819171704.z3avr2b5jur6dohl@skbuf>
Date:   Thu, 19 Aug 2021 17:17:05 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
CC:     "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Horatiu Vultur <horatiu.vultur@...rochip.com>,
        Rob Herring <robh+dt@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH devicetree 2/2] MIPS: mscc: ocelot: mark the phy-mode for
 internal PHY ports

On Thu, Aug 19, 2021 at 08:04:16PM +0300, Vladimir Oltean wrote:
> The ocelot driver was converted to phylink, and that expects a valid
> phy_interface_t. Without a phy-mode, of_get_phy_mode returns
> PHY_INTERFACE_MODE_NA, which is not ideal because phylink rejects that.
> 
> The ocelot driver was patched to treat PHY_INTERFACE_MODE_NA as
> PHY_INTERFACE_MODE_INTERNAL to work with the broken DT blobs, but we
> should fix the device trees and specify the phy-mode too.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> ---

Please note that the pre-phylink driver has this check:

		switch (ocelot_port->phy_mode) {
		case PHY_INTERFACE_MODE_NA:
			(...)
		case PHY_INTERFACE_MODE_SGMII:
			(...)
		case PHY_INTERFACE_MODE_QSGMII:
			(...)
		default:
			dev_err(ocelot->dev,
				"invalid phy mode for port%d, (Q)SGMII only\n",
				port);
			of_node_put(portnp);
			err = -EINVAL;
			goto out_teardown;
		}

So it does not actually expect PHY_INTERFACE_MODE_INTERNAL and will
error out.

Are we okay with the new device tree blobs breaking the old kernel?

Should we instead wait for a few more kernel release cycles before
changing the device tree in this regard?