On Tue, Oct 20, 2020 at 09:24:04PM +0000, Chris Packham wrote:
>
> On 20/10/20 11:18 pm, Russell King - ARM Linux admin wrote:
> > On Tue, Oct 20, 2020 at 04:45:58PM +1300, Chris Packham wrote:
> >> +void mv88e6123_serdes_get_regs(struct mv88e6xxx_chip *chip, int port,
> >> void *_p)
> >> +{
> >> + u16 *p = _p;
> >> + u16 reg;
> >> + int i;
> >> +
> >> + if (mv88e6xxx_serdes_get_lane(chip, port) == 0)
> >> + return;
> >> +
> >> + for (i = 0; i < 26; i++) {
> >> + mv88e6xxx_phy_read(chip, port, i, ®);
> > Shouldn't this deal with a failed read in some way, rather than just
> > assigning the last or possibly uninitialised value to p[i] ?
>
> mv88e6390_serdes_get_regs() and mv88e6352_serdes_get_regs() also ignore
> the error. The generic mv88e6xxx_get_regs() memsets p[] to 0xff so if
> the serdes_get_regs functions just left it alone we'd return 0xffff
> which is probably better than repeating the last value although it's
> still ambiguous because 0xffff is a valid value for plenty of these
> registers.
>
> Since it looks like I need to come up with an alternative to patch #1
> I'll concentrate on that but making the serdes_get_regs() a little more
> error tolerant is a cleanup I can easily tack on onto this series.
Yep, it looks like they all suffer the same problem. Interestingly,
mv88e6xxx_get_regs() does handle the error by avoiding writing the
register entry (so it gets left as 0xffff.)
Incidentally, that's also the value you'll get when reading from a
PHY that doesn't respond, since the MDIO data line is pulled high
when undriven.
--
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