Re: [PATCH v1 1/2] phy: keystone: serdes driver for gbe 10gbe and pcie

Arnd Bergmann
2015-10-15T20:53:31Z

On Thursday 15 October 2015 20:08:32 Kwok, WingMan wrote:
>
> > > +#define reg_rmw(addr, value, mask) \
> > > + __raw_writel(((__raw_readl(addr) & (~(mask))) | \
> > > + (value & (mask))), (addr))
> >
> > not endian safe, and potentially racy.
> >
>
> will change to
>
> #define reg_rmw(addr, value, mask) \
> writel(((readl(addr) & (~(mask))) | \
> (value & (mask))), (addr))

Ok, sounds good. Note that if any of this is performance critical,
better use readl_relaxed(), but as long as this is just for setup
code and not for data transfers, staying with readl() as you
suggest is better.

> > > +static inline void _kserdes_reset_cdr(void __iomem *sregs, int lane)
> > > +{
> > > + /* toggle signal detect */
> > > + _kserdes_force_signal_detect_low(sregs, lane);
> > > + mdelay(1);
> > > + _kserdes_force_signal_detect_high(sregs, lane);
> > > +}
> >
> > Can you change the code so you can use msleep(1) here?
> >
>
> will replace delays with usleep_range()

Ok.

> > > +
> > > + do {
> > > + mdelay(10);
> > > + memset(lane_down, 0, sizeof(lane_down));
> > > +
> > > + link_up = _kserdes_check_link_status(dev, sregs,
> > > + pcsr_regmap, lanes,
> > > + lanes_enable,
> > > + current_state, lane_down);
> > > +
> > > + /* if we did not get link up then wait 100ms
> > > + * before calling it again
> > > + */
> > > + if (link_up)
> > > + break;
> > > +
> > > + for (i = 0; i < lanes; i++) {
> > > + if ((lanes_enable & (1 << i)) && lane_down[i])
> > > + dev_dbg(dev,
> > > + "XGE: detected lane down on lane %d\n",
> > > + i);
> > > + }
> > > +
> > > + if (++retries > 100)
> > > + return -ETIMEDOUT;
> > > +
> > > + } while (!link_up);
> >
> > an more importantly here. Blocking the CPU for over one second is not good.
> >
> > Any use of mdelay() should have a comment explaining why you cannot use
> > msleep() in that instance.
> >
>
> will replace delays with usleep_range()

Here you have to be careful with the total runtime. Using usleep_range()
is a good idea, and you can have a particularly wide range, but then you
should changen the timeout condition from number of retries to total
elapsed time like

unsigned long timeout = jiffies + HZ; /* 1 second maximum */
do {
...

if (link_up)
break;

if (time_after(jiffies, timeout)
return -ETIMEOUT;

usleep_range(1000, 50000);
} while (1);

Arnd