Re: SMSC9730 Autosuspend/Resume Questions

[Frieder Schrempf]

Hi Nisar,

On 22.10.18 09:03, Nisar.Sayed@xxxxxxxxxxxxx wrote:
> Hi Frieder,
>
> > Hi,
> >
> > I recently tested a board with SMSC9730 connected via USB HSIC to an
> > i.MX6S SOC. I used these patches on top of v4.14-rc8 for the USB HSIC
> > support: [1].
> >
> > When I turned on autosuspend, the smsc95xx stopped in the middle of the
> > suspending routine and /sys/bus/usb/devices/usb3/3-
> > 1/power/runtime_status reported "suspending"
> > forever.
> >
> > With some debug logs I found out, that the last line of code that was
> > executed is [2], after that I didn't get any further messages.
> >
> > Then I applied the following diff and the suspend/resume started to work
> > reliably:
> >
> > @@ -1382,10 +1385,11 @@ static int smsc95xx_link_ok_nopm(struct usbnet
> > *dev)
> >           ret = smsc95xx_mdio_read_nopm(dev->net, mii->phy_id, MII_BMSR);
> >           if (ret < 0)
> >                   return ret;
> > -
> > +       /*
> >           ret = smsc95xx_mdio_read_nopm(dev->net, mii->phy_id, MII_BMSR);
> >           if (ret < 0)
> >                   return ret;
> > +       */
> >
> >           return !!(ret & BMSR_LSTATUS);
> >    }
> >
> > So it seems like the dummy read, that is commented with "first, a dummy
> > read, needed to latch some MII phys" causes problems in my setup. Do you
> > have an idea what could be the reason? Is this a proper fix?
>   
> Link status bit is latch low register and needs to be read twice. You may get wrong Link status with this fix.

Ok, thanks for the information. I guess I'll have to do some more 
debugging to find out why the second read fails in my case.

Frieder