netdev - Re: "asix: Don't reset PHY on if_up for ASIX 88772" breaks net on arndale platform

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Message-ID: <20141106100104.GS23178@opensource.wolfsonmicro.com>
Date:	Thu, 6 Nov 2014 10:01:04 +0000
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	Riku Voipio <riku.voipio@....fi>
Cc:	"Stam, Michel [FINT]" <M.Stam@...ro.nl>, freddy@...x.com.tw,
	davem@...emloft.net, linux-usb@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org
Subject: Re: "asix: Don't reset PHY on if_up for ASIX 88772" breaks net on
	arndale platform

On Thu, Nov 06, 2014 at 11:06:51AM +0200, Riku Voipio wrote:
> On Wed, Nov 05, 2014 at 03:02:58PM +0000, Charles Keepax wrote:
> > On Wed, Nov 05, 2014 at 01:04:37PM +0100, Stam, Michel [FINT] wrote:
> > > Hello Charles,
> > > 
> > > After looking around I found the reset value for the 8772 chip, which
> > > seems to be 0x1E1 (ANAR register).
> > > 
> > > This equates to (according to include/uapi/linux/mii.h)
> > > ADVERTISE_ALL | ADVERTISE_CSMA.
> > > 
> > > The register only seems to become 0 if the software reset fails.
>  
> > Odd it definitely reads back as zero on Arndale. I am guessing
> > that the root of the problem here is that for some reason Arndale
> > POR of the ethernet is pants and it needs a full software reset
> > before it will work and the patch removes the full reset
> > callback.
> 
> The asix on arndale comes semi-configured from u-boot, which I guess is
> not the state kernel expects it to come in. At least in my case where
> I use tftp from u-boot to load my kernel.
> 
> So probably the full reset is needed here to make the asix chip come
> to a truly pristine state.
> 
> The commit that Michel partially reverted (by returning to use
> ax88772_link_reset instead of ax88772_reset), indicates that a strong reset
> is needed for suspend/resume as well:

Ok I think I have cracked this one. I am pretty sure you are
right that the USB comes to us in a strange state and needs
a full reset, but that only needs to happen once when the driver
is bound in. So there is some code in ax88772_bind that appears
to try to reset the device but does a lot less than ax88772_reset
and I think that must be the problem. Applying the following on
top of the patch we have been debating I think will make
everything work for all of us:

--- a/drivers/net/usb/asix_devices.c
+++ b/drivers/net/usb/asix_devices.c
@@ -465,19 +465,7 @@ static int ax88772_bind(struct usbnet *dev,
struct usb_interface *in
                return ret;
        }

-       ret = asix_sw_reset(dev, AX_SWRESET_IPPD | AX_SWRESET_PRL);
-       if (ret < 0)
-               return ret;
-
-       msleep(150);
-
-       ret = asix_sw_reset(dev, AX_SWRESET_CLEAR);
-       if (ret < 0)
-               return ret;
-
-       msleep(150);
-
-       ret = asix_sw_reset(dev, embd_phy ? AX_SWRESET_IPRL : AX_SWRESET_PRTE);
+       ax88772_reset(dev);

If you guys could test that and let me know how you get on I will
send in a proper patch if it looks good.

Thanks,
Charles
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