linux-kernel - Re: GPIO registration for external Ethernet PHY oscillator enable/disable

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Date:	Tue, 7 Oct 2014 11:38:44 -0500
From:	Michael Welling <mwelling@...cinc.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Florian Fainelli <f.fainelli@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Greg KH <gregkh@...uxfoundation.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: GPIO registration for external Ethernet PHY oscillator
 enable/disable

On Tue, Oct 07, 2014 at 04:09:45PM +0200, Linus Walleij wrote:
> On Fri, Sep 26, 2014 at 10:04 PM, Michael Welling <mwelling@...cinc.com> wrote:
> > On Fri, Sep 26, 2014 at 10:16:51AM -0700, Florian Fainelli wrote:
> >>
> >> Yes and no, this might feel like the wrong place, but ultimately, the
> >> Ethernet MAC is a consumer of the PHY device, and is in control, through
> >> the PHY library of how and when the PHY gets to be powered off.
> >>
> >
> > So here is the patch that I made that hooks into the macb driver.
> >
> > Please look it over and tell me if we are on the same page.
> >
> > The thing that bothers me about this solution is that it will only work with the macb driver.
> > So everytime I use the same PHY/OSC combo with a different SoC I will have to do another patch.
> >
> > diff --git a/drivers/net/ethernet/cadence/macb.c b/drivers/net/ethernet/cadence/macb.c
> > index e4e34b6..8cd363f 100644
> > --- a/drivers/net/ethernet/cadence/macb.c
> > +++ b/drivers/net/ethernet/cadence/macb.c
> > @@ -28,6 +28,7 @@
> >  #include <linux/of.h>
> >  #include <linux/of_device.h>
> >  #include <linux/of_net.h>
> > +#include <linux/of_gpio.h>
> 
> No please,
> #include <linux/gpio/consumer.h>
> 
> > @@ -1833,6 +1834,16 @@ static int __init macb_probe(struct platform_device *pdev)
> >                 bp->phy_interface = err;
> >         }
> >
> > +       bp->phy_osc_gpio = of_get_named_gpio(pdev->dev.of_node, "osc-gpio", 0);
> > +
> > +       if (gpio_is_valid(bp->phy_osc_gpio))
> > +       {
> > +               if (gpio_request(bp->phy_osc_gpio, "osc-gpio") != 0) {
> > +                       pr_info("Oscillator GPIO not available.\n");
> > +                       bp->phy_osc_gpio = 0;
> > +               }
> > +       }
> 
> 
> No,
> bp->phy_osc_gpiod = devm_gpiod_get(&pdev->dev, "osc-gpio", 0);
> 
> And error handling.
> 
> > +       if (gpio_is_valid(bp->phy_osc_gpio))
> > +               gpio_set_value_cansleep(bp->phy_osc_gpio, 0);
> > +
> 
> if (bp->phy_osc_gpiod)
>   gpiod_set_...
> 
> > +       if (gpio_is_valid(bp->phy_osc_gpio))
> > +               gpio_set_value_cansleep(bp->phy_osc_gpio, 1);
> 
> Dito.
> 
> >         phy_interface_t         phy_interface;
> > +       int                     phy_osc_gpio;
> 
> struct gpio_desc *phy_osc_gpiod;

Thank you for clearifying the preferred/correct interface.

This version was not even functional and I had to update it 
such that it was.

I will, of course, follow the above suggestions if/when I submit an
actual patch.

I am still not sure the MAC driver is the best place for this
registration.

> 
> Yours,
> Linus Walleij
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