From: Heiko =?ISO-8859-1?Q?St=FCbner?= <heiko@sntech.de>
To: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc: Caesar Wang <wxt@rock-chips.com>, "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh+dt@kernel.org>, linux-rockchip@lists.infradead.org,
        keescook@google.com, leozwang@google.com,
        Alexander Kochetkov <al.kochet@gmail.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/6] net: arc_emac: support the phy reset for emac driver
Date: Fri, 11 Mar 2016 15:59:16 +0100
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Am Freitag, 11. M?rz 2016, 15:56:04 schrieb Heiko St?bner:
> Hi Caesar,
> 
> Am Freitag, 11. M?rz 2016, 16:47:59 schrieb Sergei Shtylyov:
> > On 3/11/2016 1:55 PM, Caesar Wang wrote:
> > > This patch adds to support the emac phy reset.
> > > 
> > > 1) phy-reset-gpios:
> > > The phy-reset-gpios is an optional property for arc emac device tree
> > > boot.
> > > Change the binding document to match the driver code.
> > > 
> > > 2) phy-reset-duration:
> > > Different boards may require different phy reset duration. Add property
> > > phy-reset-duration for device tree probe, so that the boards that need
> > > a longer reset duration can specify it in their device tree.
> > > 
> > > 3) phy-reset-active-high:
> > > We need that for a custom hardware that needs the reverse reset
> > > sequence.
> > > 
> > > Of course, this patch will fix the issue on
> > > https://patchwork.kernel.org/patch/8186801/.
> > > 
> > > In some cases, the emac couldn't work if you don't have reset the phy.
> > > Let's add it to happy work.
> > > 
> > > Signed-off-by: Caesar Wang <wxt@rock-chips.com>
> > > ---
> > > 
> > >   drivers/net/ethernet/arc/emac_main.c | 41
> > >   ++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+)
> > > 
> > > diff --git a/drivers/net/ethernet/arc/emac_main.c
> > > b/drivers/net/ethernet/arc/emac_main.c index 6446af1..42384f6a 100644
> > > --- a/drivers/net/ethernet/arc/emac_main.c
> > > +++ b/drivers/net/ethernet/arc/emac_main.c
> > > @@ -764,6 +764,45 @@ static const struct net_device_ops
> > > arc_emac_netdev_ops = {>
> > > 
> > >   #endif
> > >   };
> > > 
> > > +#ifdef CONFIG_OF
> > > +static void emac_reset_phy(struct net_device *pdev)
> > > +{
> > > +	int err, phy_reset;
> > > +	bool active_high = false;
> > > +	int msec = 10;
> > > +	struct device *dev = pdev->dev.parent;
> > > +	struct device_node *np = dev->of_node;
> > > +
> > > +	if (!np)
> > > +		return;
> > > +
> > > +	of_property_read_u32(np, "phy-reset-duration", &msec);
> > > +	/* A sane reset duration should not be longer than 1s */
> > > +	if (msec > 1000)
> > > +		msec = 1;
> > > +
> > > +	phy_reset = of_get_named_gpio(np, "phy-reset-gpios", 0);
> > > +	if (!gpio_is_valid(phy_reset))
> > > +		return;
> > > +
> > > +	active_high = of_property_read_bool(np, "phy-reset-active-high");
> > > +
> > > +	err = devm_gpio_request_one(dev, phy_reset, active_high ?
> > > +				    GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW,
> > > +				    "phy-reset");
> > > +	if (err) {
> > > +		dev_err(dev, "failed to get phy-reset-gpios: %d\n", err);
> > > +		return;
> > > +	}
> > > +	msleep(msec);
> > > +	gpio_set_value_cansleep(phy_reset, !active_high);
> > > +}
> > 
> > [...]
> > 
> >     Why not make it the mii_bus::reset() method? It gets called before the
> > 
> > MDIO bus scan.
> 
> while meddling with the emac, I've built some sort of preliminary variant of
> Sergei's suggestion at [0] - maybe you could take a look for some sort of
> inspiration ;-)

forgot to add ... of course the newer gpiod_* infrastructure should be used 
instead of the old integer-based gpio numbers

> 
> The code is lifted from the designware gmac driver, so the binding also is
> similar.
> 
> 
> Heiko
> 
> 
> [0]
> https://github.com/mmind/linux-rockchip/commit/a943c588783438ff1c508dfa8c79
> f1709aa5775e