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Date: Sat, 14 May 2016 22:36:38 +0300 From: Sergei Shtylyov <sergei.shtylyov@...entembedded.com> To: Andrew Lunn <andrew@...n.ch> Cc: Roger Quadros <rogerq@...com>, Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, grant.likely@...aro.org, robh+dt@...nel.org, devicetree@...r.kernel.org, f.fainelli@...il.com, netdev@...r.kernel.org, frowand.list@...il.com, pawel.moll@....com, mark.rutland@....com, ijc+devicetree@...lion.org.uk, galak@...eaurora.org, linux-kernel@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org> Subject: Re: [PATCH RFT 1/2] phylib: add device reset GPIO support Hello. On 05/14/2016 02:44 AM, Andrew Lunn wrote: >>>>> Another issue is that on some boards we have one reset line tied to >>>>> multiple PHYs.How do we prevent multiple resets being taking place when each of >>>>> the PHYs are registered? >>>> >>>> My patch just doesn't address this case -- it's about the >>>> individual resets only. >>> >>> This actually needs to be addresses a layer above. What you have is a >>> bus reset, not a device reset. >> >> No. >> There's simply no such thing as a bus reset for the xMII/MDIO >> busses, there's simply no reset signaling on them. Every device has >> its own reset signal and its own timing requirements. > > Except in the case above, where two phys are sharing the same reset > signal. So although it is not part of the mdio standard to have a bus > reset, this is in effect what the gpio line is doing, resetting all > devices on the bus. If you don't model that as a bus reset, how do you > model it? I'm not suggesting that the shared reset should be handled by my patch. Contrariwise, I suggested to use the mii_bus::reset() method -- I see it as a necessary evil. However, in the more common case of a single PHY, this method simply doesn't scale -- you'd have to teach each and every individual MAC/ MDIO driver to do the GPIO reset trick. > Andrew MBR, Sergei
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