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Date: Thu, 3 Sep 2020 22:39:11 +0200 From: Andrew Lunn <andrew@...n.ch> To: Florian Fainelli <f.fainelli@...il.com> Cc: netdev@...r.kernel.org, adam.rudzinski@....net.pl, m.felsch@...gutronix.de, hkallweit1@...il.com, richard.leitner@...data.com, zhengdejin5@...il.com, devicetree@...r.kernel.org, kernel@...gutronix.de, kuba@...nel.org, robh+dt@...nel.org Subject: Re: [PATCH net-next 1/3] net: phy: Support enabling clocks prior to bus probe On Wed, Sep 02, 2020 at 09:39:45PM -0700, Florian Fainelli wrote: > Some Ethernet PHYs may require that their clock, which typically drives > their logic to respond to reads on the MDIO bus be enabled before > issusing a MDIO bus scan. issuing > > We have a chicken and egg problem though which is that we cannot enable > a given Ethernet PHY's device clock until we have a phy_device instance > create and called the driver's probe function. This will not happen > unless we are successful in probing the PHY device, which requires its > clock(s) to be turned on. > > For DT based systems we can solve this by using of_clk_get() which > operates on a device_node reference, and make sure that all clocks > associaed with the node are enabled prior to doing any reads towards the associated. > device. In order to avoid drivers having to know the a priori reference > count of the resources, we drop them back to 0 right before calling > ->probe() which is then supposed to manage the resources normally. Andrew
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