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Date: Wed, 26 Aug 2020 10:58:57 +0200 From: Sascha Hauer <s.hauer@...gutronix.de> To: Andrew Lunn <andrew@...n.ch> Cc: netdev@...r.kernel.org, Florian Fainelli <f.fainelli@...il.com>, Heiner Kallweit <hkallweit1@...il.com>, kernel@...gutronix.de Subject: Re: ethernet-phy-ieee802.3-c22 binding and reset-gpios Hi Andrew, On Tue, Aug 25, 2020 at 03:14:00PM +0200, Andrew Lunn wrote: > On Tue, Aug 25, 2020 at 11:09:33AM +0200, Sascha Hauer wrote: > > Hi All, > > > > I am using the ethernet phy binding here that looks like: > > > > ethphy1: ethernet-phy@1 { > > compatible = "ethernet-phy-ieee802.3-c22"; > > reg = <1>; > > eee-broken-1000t; > > reset-gpios = <&gpio4 2 GPIO_ACTIVE_LOW>; > > }; > > > > It seems the "reset-gpios" is inherently broken in Linux. > > Hi Sascha > > I think it would be better to say, it does not do what people expect, > rather than broken. > > This code was developed for a PHY which needed to be reset after > enumeration. That PHY did enumerate, either because it was not held in > reset, or would still answer ID requests while held in reset. > > It does however not work for PHYs which are held in reset during probe > and won't enumerate. This is a known issues, but could be better > documented. I think the behaviour should rather be improved than documented. > > > Is this the path to go or are there any other ideas how to solve > > this issue? > > There is two different reset gpios in DT. There is a per PHY reset, > which you are trying to use. And a per MDIO bus reset, which should > apply to all PHYs on the bus. This per bus reset works more as > expected. If this works for you, you could use that. Well there is only one phy connected to the bus, so it makes no difference if I say the reset GPIO is for the whole bus or for a single phy only. The per bus reset should work, but currently it doesn't. First reason I found out that mdiobus_register() doesn't handle -EPROBE_DEFER returned by the devm_gpiod_get_optional() properly, patch follows. Second reason is that the phy is not detected (id read returns 0xffff) when the reset is attached to the bus. So far I haven't found the reason for that. > > Otherwise, you need to modify of_mdiobus_register() to look in device > tree while it is performing the scan and see if there is a reset > property for each address on the bus. If so, take the device out of > reset before reading the ID registers. Ok. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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